The HRPT2 tumor suppressor gene product parafibromin associates with human PAF1 and RNA polymerase II

Genetics of hereditary forms of primary hyperparathyroidism

Primary hyperparathyroidism (PHPT), a relatively common disorder characterized by hypercalcemia with raised or inappropriately normal serum parathyroid hormone (PTH) concentrations, may occur as part of a hereditary syndromic disorder or as a non-syndromic disease. The associated syndromic disorders include multiple endocrine neoplasia types 1-5 (MEN1-5) and hyperparathyroidism with jaw tumor (HPT-JT) syndromes, and the non-syndromic forms include familial hypocalciuric hypercalcemia types 1-3 (FHH1-3), familial isolated hyperparathyroidism (FIHP), and neonatal severe hyperparathyroidism (NS-HPT). Such hereditary forms may occur in > 10% of patients with PHPT, and their recognition is important for implementation of gene-specific screening protocols and investigations for other associated tumors. Syndromic PHPT tends to be multifocal and multiglandular with most patients requiring parathyroidectomy with the aim of limiting end-organ damage associated with hypercalcemia, particularly osteoporosis, nephrolithiasis, and renal failure. Some patients with non-syndromic PHPT may have mutations of the MEN1 gene or the calcium-sensing receptor (CASR), whose loss of function mutations usually cause FHH1, a disorder associated with mild hypercalcemia and may follow a benign clinical course. Measurement of the urinary calcium-to-creatinine ratio clearance (UCCR) may help to distinguish patients with FHH from those with PHPT, as the majority of FHH patients have low urinary calcium excretion (UCCR < 0.01). Once genetic testing confirms a hereditary cause of PHPT, further genetic testing can be offered to the patients' relatives and subsequent screening can be carried out in these affected family members, which prevents inappropriate testing in normal individuals.

Insights into Hyperparathyroidism-Jaw Tumour Syndrome: From Endocrine Acumen to the Spectrum of CDC73 Gene and Parafibromin-Deficient Tumours

A total of 1 out of 10 patients with primary hyperparathyroidism (PHP) presents an underlying genetic form, such as multiple endocrine neoplasia types 1, 2A, etc., as well as hyperparathyroidism-jaw tumour syndrome (HJT). We aimed to summarise the recent data, thus raising more awareness regarding HJT, from the clinical perspective of PHP in association with the challenges and pitfalls of CDC73 genetic testing and parafibromin staining. This narrative review included a sample-focused analysis from the past decade according to a PubMed search. We identified 17 original human studies (≥4 patients per article). The mean age at disease onset was between 20.8 and 39.5 years, while the largest study found that 71% of patients had HJT recognised before the age of 30. Males and females seemed to be equally affected, in contrast with sporadic PHP. PHP represented the central manifestation of HJT, occurring as the first manifestation in up to 85% of HJT cases. A biochemistry panel found a mean serum calcium level above the level of 12 mg/dL in PHP. PTH was elevated in HJT as well, with average values of at least 236.6 pg/mL. The most frequent pathological type in PHP was a parathyroid adenoma, but the incidence of a parathyroid carcinoma was much higher than in non-HJT cases (15% of all parathyroid tumours), with the diagnosis being established between the age of 15 and 37.5. In some families up to 85% of carriers suffered from a parathyroid carcinoma thus indicating that certain CDC73 pathogenic variants may harbour a higher risk. An important issue in HJT was represented by the parafibromin profile in the parathyroid tumours since in HJT both parathyroid adenomas and carcinomas might display a deficient immunoreactivity. Another frequent manifestation in HJT was ossifying fibromas of the jaw (affecting 5.4% to 50% of patients; the largest study found a prevalence of 15.4%). HJT was associated with a wide variety of kidney lesion (mostly: kidney cysts, with a prevalence of up to 75%, and renal tumours involved in 19% of patients). The risk of uterine lesions seemed increased in HJT, especially with concern to leiomyomas, adenofibromas, and adenomyosis. The underlying pathogenic mechanisms and the involvement of CDC73 pathogenic variants and parafibromin expression are yet to be explored. Currently, the heterogeneous expression of parafibromin status and, the wide spectrum of CDC73 mutations including the variety of clinical presentations in HJT, make it difficult to predict the phenotype based on the genotype. The central role of HJT-PHP is, however, the main clinical element, while the elevated risk of parathyroid carcinoma requires a special awareness.

Phenotype of Parathyroid-targeted Cdc73 Deletion in Mice Is Strain-dependent

Hyperparathyroidism jaw-tumor syndrome is an autosomal dominant disorder caused by mutations in the CDC73/HRPT2 tumor suppressor gene, encoding parafibromin, and manifesting benign or malignant parathyroid tumors, ossifying jaw fibromas, uterine tumors, and kidney lesions. Sporadic parathyroid carcinomas also frequently exhibit inactivating CDC73 mutations and loss of parafibromin. To study the role of CDC73 in parathyroid cell proliferation in vivo, we generated mice with a parathyroid-specific deletion of Cdc73. Homozygous knockout mice on a mixed B6/129/CD1 background had decreased serum calcium and PTH and smaller parathyroid glands compared with heterozygous or wild-type littermates, whereas homozygous Cdc73-null mice on other backgrounds exhibited no abnormalities in parathyroid gland function or development. No hypercalcemia or parathyroid hypercellularity was observed in mice of any background examined at any age. Thus, although postnatally acquired complete loss of CDC73 causes parathyroid cell proliferation and hyperparathyroidism, such as seen in human hyperparathyroidism jaw-tumor syndrome, our results suggest that earlier, developmentally imposed complete loss of Cdc73 can cause a primary defect in parathyroid gland structure/function in a strain-dependent manner. This striking disparity in parathyroid phenotype related to genetic background offers a unique opportunity in an in vivo model system to precisely dissect and identify the responsible molecular mechanisms.

Phenotypic Profiling and Molecular Mechanisms in Hyperparathyroidism-jaw Tumor Syndrome

CONTEXT

Hyperparathyroidism-jaw tumor (HPT-JT) syndrome is a heritable form of primary hyperparathyroidism caused by germline inactivating mutations in CDC73 encoding parafibromin and is associated with an increased risk of parathyroid cancer. There is little evidence to guide the management of patients with the disease.

OBJECTIVE

(1) Characterize the natural history of HPT-JT, (2) correlate genotype and histology of parathyroid tumors with parafibromin immunostaining, (3) understand molecular changes downstream to CDC73 loss.

DESIGN

Retrospective study of patients with HPT-JT syndrome (genetically confirmed or affected first-degree relatives). Independent review of uterine tumor from 2 patients and staining for parafibromin on parathyroid tumors from 19 patients (13 adenomas, 6 carcinomas) was performed. RNA-sequencing was performed in 21 parathyroid samples (8 HPT-JT-related adenomas, 6 HPT-JT-related carcinomas, and 7 sporadic carcinomas with wild-type CDC73).

RESULTS

We identified 68 patients from 29 kindreds with HPT-JT with median age at last follow-up of 39 [interquartile range, 29-53] years. A total of 55/68 (81%) developed primary hyperparathyroidism; 17/55 (31%) had parathyroid carcinoma. Twelve of 32 (38%) females developed uterine tumors. Of the 11 patients who had surgical resection for uterine tumors, 12/24 (50%) tumors were rare mixed epithelial mesenchymal polypoid lesions. Four of 68 patients (6%) developed solid kidney tumors; 3/4 had a CDC73 variant at p.M1 residue. Parafibromin staining of parathyroid tumors did not correlate with tumor histology or genotype. RNA-sequencing showed a significant association of HPT-JT-related parathyroid tumors with transmembrane receptor protein tyrosine kinase signaling pathway, mesodermal commitment pathway, and cell-cell adhesion.

CONCLUSIONS

Multiple, recurrent atypical adenomyomatous uterine polyps appear to be enriched in women with HPT-JT and appear characteristic of the disease. Patients with CDC73 variants at p.M1 residue appear predisposed to kidney tumors.

CLINICAL TRIAL NUMBER

NCT04969926.

Molecular and Clinical Spectrum of Primary Hyperparathyroidism

Recent data suggest an increase in the overall incidence of parathyroid disorders, with primary hyperparathyroidism (PHPT) being the most prevalent parathyroid disorder. PHPT is associated with morbidities (fractures, kidney stones, chronic kidney disease) and increased risk of death. The symptoms of PHPT can be nonspecific, potentially delaying the diagnosis. Approximately 15% of patients with PHPT have an underlying heritable form of PHPT that may be associated with extraparathyroidal manifestations, requiring active surveillance for these manifestations as seen in multiple endocrine neoplasia type 1 and 2A. Genetic testing for heritable forms should be offered to patients with multiglandular disease, recurrent PHPT, young onset PHPT (age ≤40 years), and those with a family history of parathyroid tumors. However, the underlying genetic cause for the majority of patients with heritable forms of PHPT remains unknown. Distinction between sporadic and heritable forms of PHPT is useful in surgical planning for parathyroidectomy and has implications for the family. The genes currently known to be associated with heritable forms of PHPT account for approximately half of sporadic parathyroid tumors. But the genetic cause in approximately half of the sporadic parathyroid tumors remains unknown. Furthermore, there is no systemic therapy for parathyroid carcinoma, a rare but potentially fatal cause of PHPT. Improved understanding of the molecular characteristics of parathyroid tumors will allow us to identify biomarkers for diagnosis and novel targets for therapy.

Preoperative, Intraoperative, and Postoperative Parathyroid Pathology: Clinical Pathologic Collaboration for Optimal Patient Management

Parathyroid disease typically presents with parathyroid hyperfunction as result of neoplasia or a consequence of non-neoplastic systemic disease. Given the parathyroid gland is a hormonally active organ with broad physiologic implications and serologically accessible markers for monitoring, the diagnosis of parathyroid disease is predominantly a clinical pathologic correlation. We provide the current pathological correlates of parathyroid disease and discuss preoperative, intraoperative, and postoperative pathology consultative practice for optimal patient care.

Advances and Updates in Parathyroid Pathology

Hyperparathyroidism is a common endocrine disorder characterized by elevated levels of parathyroid hormone and hypercalcemia and is divided into 3 types: primary, secondary, and tertiary. Distinction between these types is accomplished by correlation of clinical, radiologic, and laboratory findings with pathologic features. Primary hyperparathyroidism occurs sporadically in 85% of cases with the remaining cases associated with multiple familial syndromes. The pathologic manifestations of primary hyperparathyroidism include parathyroid adenoma, parathyroid hyperplasia, and parathyroid carcinoma. Recent advances in the understanding of the pathogenesis of parathyroid disease has helped to refine the diagnosis and classification of parathyroid lesions. The identification of multiple clonal proliferations in traditional multiglandular parathyroid hyperplasia has led to the adoption by the World Health Organization (WHO) of the alternate term of primary hyperparathyroidism-related multiglandular parathyroid disease. Additional nomenclature changes include the adoption of the term atypical parathyroid tumor in lieu of atypical parathyroid adenoma to reflect the uncertain malignant potential of these neoplasms. Clinical and morphologic features characteristic of familial disease have been described that can help the practicing pathologist identify underlying familial disease and provide appropriate management. Use of ancillary immunohistochemistry and molecular studies can be helpful in classifying parathyroid neoplasms. Parafibromin has proven useful as a diagnostic and prognostic marker in atypical parathyroid tumors and parathyroid carcinomas. This review provides an update on the diagnosis and classification of parathyroid lesions considering the recent advances in the understanding of the molecular and clinical features of parathyroid disease and highlights the use of ancillary studies (immunohistochemical, and molecular) to refine the diagnosis of parathyroid lesions.

Parathyroid carcinoma during pregnancy: a novel pathogenic CDC73 mutation - a case report

BACKGROUND

Parathyroid carcinoma is an uncommon cause of PTH-dependent hypercalcemia. Only a handful of cases have been reported of parathyroid carcinoma during pregnancy.

CASE PRESENTATION

Twenty-four - Year - old female presented with proximal myopathy was found to have hypercalcemia. Her serum corrected total calcium was - 15 mg/dl (8.5 - 10.3), serum phosphate - 2.3 mg/dl (2.5 - 4.5), intact PTH - 118 pg/ml (20 - 80), Vitamin D - 15 ng/ml and Urine Ca/Cr ratio - 2.1 (0.1 - 0.2). Her CECT-neck revealed a well-defined mass lesion posterior to the right lobe of the thyroid - 2.6 cm × 2.5 cm × 2.9 cm in size. She was started on vitamin D supplementation, and she underwent right lower focal parathyroidectomy. Her PTH levels normalized following surgery. Her histology revealed an atypical parathyroid adenoma. She was treated with calcium and vitamin D. Her follow up was uneventful. One year following initial surgery the patient became pregnant and at 16 weeks of POA, the patient presented with a rapidly enhancing neck mass for one week duration. Her biochemical investigations were suggestive of a recurrence of primary hyperparathyroidism. Her ultrasound scan of the neck revealed a well-defined discreate hypoechoic nodule, superior to the thyroid isthmus which was confirmed by a non-contrast MRI scan of the neck. She underwent an uncomplicated second trimester parathyroid tumour excision with normalization of post op PTH. Her histology revealed a parathyroid carcinoma with vascular and capsular invasion. Her genetic studies revealed a novel frameshift mutation of the CDC73 gene. She was treated with calcium and vitamin D supplementation and closely followed up with ionized calcium and PTH levels which were normal throughout the pregnancy. She had an uncomplicated caesarean section at a POA of 37 weeks. Currently she is twelve weeks post-partum, in remission of disease.

CONCLUSION

This case shows the importance of stringent follow up of atypical parathyroid adenoma patients, the benefit of second trimester surgery in management of hypercalcemia due to parathyroid carcinoma during pregnancy and the importance of identifying the novel CDC73 gene mutation.

A two-generation hyperparathyroidism-jaw tumor (HPT-JT) syndrome family: clinical presentations, pathological characteristics and genetic analysis: a case report

Background

Hyperparathyroidism-Jaw Tumor (HPT-JT) is caused by inactivating germline mutations of CDC73. This hereditary disease can present with a range of symptoms. Jaw ossifying fibroma (OF) is one of the most important clinical presentations, affecting 30% of HPT-JT patients. However, OF is easily confused with other fibro-osseous lesions (FOLs) of the jaw. The correct diagnosis of HPT-JT is a real challenge and must be confirmed by genetic testing.

Case presentation

A female proband and her father suffered from multiple and recurrent FOLs in the jaw. Considering well demarcated margin and heterogeneous calcified substance lying in a variable density of fibrous stroma, we reached the diagnosis of jaw OF through radiologic and microscopic analyses. Additionally, the proband presented with chronic anemia resulting from menorrhagia, as well as renal mixed epithelial and stromal tumor (MEST). Two patients both presented with no evidence of Hyperparathyroidism (HPT). A germline start codon mutation (c.1A > G) of CDC73 was identified in them. Copy number loss at the CDC73 gene locus was verified in the jaw tumor sample of the proband.

Conclusion

Regardless of whether HPT manifestations are present, patients with heritable jaw OF may be at risk for HPT-JT. Genetic testing should be adopted to confirm the diagnosis. Early recognition of HPT-JT helps to better develop tailored treatment plans and surveillance programs.

USP37 Deubiquitinates CDC73 in HPT-JT Syndrome

The CDC73/HRPT2 gene, a defect which causes hyperparathyroidism–jaw tumor (HPT-JT) syndrome, encodes CDC73/parafibromin. We aimed to investigate whether CDC73 would be a target for ubiquitin–proteasome degradation. We cloned full-length cDNAs encoding a family of 58 ubiquitin-specific deubiquitinating enzymes (DUBs), also known as ubiquitin-specific proteases (USPs). Use of the yeast two-hybrid system then enabled us to identify USP37 as interacting with CDC73. The biochemical interaction between the USP37 and CDC73 and their reciprocal binding domains were studied. Co-localization of CDC73 and USP37 was observed in cells. CDC73 was found to be polyubiquitinated, and polyubiquitination of CDC73 was prominent in mutants. CDC73 was deubiquitinated via K48-specific ubiquitin chains by USP37, but not by the catalytically inactive USP37^C350S mutant. Observation of the binding between deletion mutants of CDC73 and USP37 revealed that the β-catenin binding site of CDC73 and the ubiquitin-interacting motifs 2 and 3 (UIM2 and 3) of USP37 were responsible for the interaction between the two proteins. Moreover, these two enzymes co-existed within the nucleus of COS7 cells. We conclude that USP37 is a DUB for CDC73 and that the two proteins interact through specific domains, suggesting that USP37 is responsible for the stability of CDC73 in HPT-JT syndrome.

A novel long-range deletion spanning CDC73 and upper-stream genes discovered in a kindred of familial primary hyperparathyroidism

PURPOSE

To confirm the exact break-point of a novel long-range deletion discovered in one female parathyroid carcinoma (PC) patient who has a strong family history suggesting familial hyperparathyroidism, and to investigate the expression of parafibromin in the patient's affected lesion.

METHODS

Clinical information of one female patient as well as five of her relatives was collected. Their genomic DNA extracted from peripheral blood went through Sanger sequencing and multiplex ligation-dependent probe amplification (MLPA). After completing whole genome sequencing (WGS), clone sequencing was also performed, whose result was aligned with standard human genome database after Sanger sequencing.

RESULTS

The medical history of recurrent hypercalcemia after parathyroidectomy and histopathological investigation confirmed that the female patient was diagnosed with PC. WGS displayed a novel 130 kb long-range deletion spanning UCHL5 to CDC73 that was later confirmed by clone sequencing. MLPA showed similar results in four of her five relatives, suggesting these people to be carriers of the same long-range deletion, and three among them had a history of primary hyperparathyroidism (PHPT) ahead of the proband's first visit.

CONCLUSIONS

We discovered a novel 130 kb long-range deletion spanning CDC73 in a family of 5 persons, and the existence of the deletion was related to PHPT and PC. Our discovery validated the role of CDC73 mutation in the occurrence of PHPT and PC, which provided new information to the genetic studies of PC.

Overview of the 2022 WHO Classification of Parathyroid Tumors

The 2022 WHO classification reflects increases in the knowledge of the underlying pathogenesis of parathyroid disease. In addition to the classic characteristic features of parathyroid neoplasms, subtleties in histologic features which may indicate an underlying genetic abnormality reflect increased understanding of the clinical manifestations, histologic, and genetic correlation in parathyroid disease. The importance of underlying genetic aberrancies is emphasized due to their significance to the care of the patient. Traditionally, the term "parathyroid hyperplasia" has been applied to multiglandular parathyroid disease; however, the concept of hyperplasia is generally no longer supported in the context of primary hyperparathyroidism since affected glands are usually composed of multiple "clonal" neoplastic proliferations. In light of these findings and management implications for patient care, the 2022 WHO classification endorses primary hyperparathyroidism-related multiglandular parathyroid disease (multiglandular multiple parathyroid adenomas) as a germline susceptibility-driven multiglandular parathyroid neoplasia. From such a perspective, pathologists can provide additional value to genetic triaging by recognizing morphological and immunohistochemical harbingers of MEN1, CDKN1B, MAX, and CDC73-related manifestations. In the current WHO classification, the term "parathyroid hyperplasia" is now used primarily in the setting of secondary hyperplasia which is most often caused by chronic renal failure. In addition to expansion in the histological features, including those that may be suggestive of an underlying genetic abnormality, there are additional nomenclature changes in the 2022 WHO classification reflecting increased understanding of the underlying pathogenesis of parathyroid disease. The new classification no longer endorses the use of "atypical parathyroid adenoma". This entity is now being replaced with the term of "atypical parathyroid tumor" to reflect a parathyroid neoplasm of uncertain malignant potential. The differential diagnoses of atypical parathyroid tumor are discussed along with the details of worrisome clinical and laboratory findings, and also features that define atypical histological and immunohistochemical findings to qualify for this diagnosis. The histological definition of parathyroid carcinoma still requires one of the following findings: (i) angioinvasion (vascular invasion) characterized by tumor invading through a vessel wall and associated thrombus, or intravascular tumor cells admixed with thrombus, (ii) lymphatic invasion, (iii) perineural (intraneural) invasion, (iv) local malignant invasion into adjacent anatomic structures, or (v) histologically/cytologically documented metastatic disease. In parathyroid carcinomas, the documentation of mitotic activity (e.g., mitoses per 10mm²) and Ki67 labeling index is recommended. Furthermore, the importance of complete submission of parathyroidectomy specimens for microscopic examination, and the crucial role of multiple levels along with ancillary biomarkers have expanded the diagnostic workup of atypical parathyroid tumors and parathyroid carcinoma to ensure accurate characterization of parathyroid neoplasms. The concept of parafibromin deficiency has been expanded upon and term "parafibromin deficient parathyroid neoplasm" is applied to a parathyroid neoplasm showing complete absence of nuclear parafibromin immunoreactivity. Nucleolar loss is considered as abnormal finding that requires further molecular testing to confirm its biological significance. The 2022 WHO classification emphasizes the role of molecular immunohistochemistry in parathyroid disease. By adopting a question-answer framework, this review highlights advances in knowledge of histological features, ancillary studies, and associated genetic findings that increase the understanding of the underlying pathogenesis of parathyroid disease that are now reflected in the updated classification and new entities in the 2022 WHO classification.

MicroRNA Profile Alterations in Parathyroid Carcinoma: Latest Updates and Perspectives

Simple Summary

Despite the considerable development of diagnostic tools, distinguishing between benign and malignant parathyroid tumors poses a significant diagnostic challenge. Epigenetic regulations, including noncoding microRNAs (miRNAs), have recently emerged as a new and promising source of biomarkers. MiRNAs are post-transcriptional regulators of gene expression. These tissue-specific molecules are known to be deregulated between cancer and normal cells. This review delineates changes in miRNA expression in parathyroid carcinoma (PC), advancing our understanding of PC tumorigenesis and emphasizing, at the same time, that miRNAs can be further exploited for diagnostic and therapeutic purposes.

Abstract

Parathyroid tumors are a genetically heterogenous group with a significant variability in clinical features. Due to a lack of specific signs and symptoms and uncertain histopathological criteria, parathyroid carcinomas (PCs) are challenging to diagnose, both before and after surgery. There is a great interest in searching for accurate molecular biomarkers for early detection, disease monitoring, and clinical management. Due to improvements in molecular pathology, the latest studies have reported that PC tumorigenesis is strongly linked to the epigenetic regulation of gene expression. MicroRNA (miRNA) profiling may serve as a helpful adjunct in distinguishing parathyroid adenoma (PAd) from PC and provide further insight into regulatory pathways involved in PTH release and parathyroid tumorigenesis. So far, only a few studies have attempted to show the miRNA signature for PC, and very few overlaps could be found between these relatively similar studies. A global miRNA downregulation was detected in PC compared with normal glands among differentially expressed miRNAs. This review summarizes changes in miRNA expression in PC and discusses the future research directions in this area.

Genetics and Epigenetics of Parathyroid Carcinoma

Parathyroid carcinoma (PC) is an extremely rare malignancy, accounting less than 1% of all parathyroid neoplasms, and an uncommon cause of primary hyperparathyroidism (PHPT), characterized by an excessive secretion of parathyroid hormone (PTH) and severe hypercalcemia. As opposed to parathyroid hyperplasia and adenomas, PC is associated with a poor prognosis, due to a commonly unmanageable hypercalcemia, which accounts for death in the majority of cases, and an overall survival rate of 78-85% and 49-70% at 5 and 10 years after diagnosis, respectively. No definitively effective therapies for PC are currently available. The mainly employed treatment for PC is the surgical removal of tumoral gland(s). Post-surgical persistent or recurrent disease manifest in about 50% of patients. The comprehension of genetic and epigenetic bases and molecular pathways that characterize parathyroid carcinogenesis is important to distinguish malignant PCs from benign adenomas, and to identify specific targets for novel therapies. Germline heterozygote inactivating mutations of the CDC73 tumor suppressor gene, with somatic loss of heterozygosity at 1q31.2 locus, account for about 50-75% of familial cases; over 75% of sporadic PCs harbor biallelic somatic inactivation/loss of CDC73. Recurrent mutations of the PRUNE2 gene, a recurrent mutation in the ADCK1 gene, genetic amplification of the CCND1 gene, alterations of the PI3K/AKT/mTOR signaling pathway, and modifications of microRNA expression profile and gene promoter methylation pattern have all been detected in PC. Here, we review the current knowledge on gene mutations and epigenetic changes that have been associated with the development of PC, in both familial and sporadic forms of this malignancy.

A comprehensive analysis of prefoldins and their implication in cancer

Prefoldins (PFDNs) are evolutionary conserved co-chaperones, initially discovered in archaea but universally present in eukaryotes. PFDNs are prevalently organized into hetero-hexameric complexes. Although they have been overlooked since their discovery and their functions remain elusive, several reports indicate they act as co-chaperones escorting misfolded or non-native proteins to group II chaperonins. Unlike the eukaryotic PFDNs which interact with cytoskeletal components, the archaeal PFDNs can bind and stabilize a wide range of substrates, possibly due to their great structural diversity. The discovery of the unconventional RPB5 interactor (URI) PFDN-like complex (UPC) suggests that PFDNs have versatile functions and are required for different cellular processes, including an important role in cancer. Here, we summarize their functions across different species. Moreover, a comprehensive analysis of PFDNs genomic alterations across cancer types by using large-scale cancer genomic data indicates that PFDNs are a new class of non-mutated proteins significantly overexpressed in some cancer types.

Pathogenic Mitochondrial DNA Mutation Load Inversely Correlates with Malignant Features in Familial Oncocytic Parathyroid Tumors Associated with Hyperparathyroidism-Jaw Tumor Syndrome

While somatic disruptive mitochondrial DNA (mtDNA) mutations that severely affect the respiratory chain are counter-selected in most human neoplasms, they are the genetic hallmark of indolent oncocytomas, where they appear to contribute to reduce tumorigenic potential. A correlation between mtDNA mutation type and load, and the clinical outcome of a tumor, corroborated by functional studies, is currently lacking. Recurrent familial oncocytomas are extremely rare entities, and they offer the chance to investigate the determinants of oncocytic transformation and the role of both germline and somatic mtDNA mutations in cancer. We here report the first family with Hyperparathyroidism-Jaw Tumor (HPT-JT) syndrome showing the inherited predisposition of four individuals to develop parathyroid oncocytic tumors. MtDNA sequencing revealed a rare ribosomal RNA mutation in the germline of all HPT-JT affected individuals whose pathogenicity was functionally evaluated via cybridization technique, and which was counter-selected in the most aggressive infiltrating carcinoma, but positively selected in adenomas. In all tumors different somatic mutations accumulated on this genetic background, with an inverse clear-cut correlation between the load of pathogenic mtDNA mutations and the indolent behavior of neoplasms, highlighting the importance of the former both as modifiers of cancer fate and as prognostic markers.

Two distinct mechanisms of RNA polymerase II elongation stimulation in vivo

Transcription by RNA polymerase II (RNA Pol II) relies on the elongation factors PAF1 complex (PAF), RTF1, and SPT6. Here, we use rapid factor depletion and multi-omics analysis to investigate how these elongation factors influence RNA Pol II elongation activity in human cells. Whereas depletion of PAF subunits PAF1 and CTR9 has little effect on cellular RNA synthesis, depletion of RTF1 or SPT6 strongly compromises RNA Pol II activity, albeit in fundamentally different ways. RTF1 depletion decreases RNA Pol II velocity, whereas SPT6 depletion impairs RNA Pol II progression through nucleosomes. These results show that distinct elongation factors stimulate either RNA Pol II velocity or RNA Pol II progression through chromatin in vivo. Further analysis provides evidence for two distinct barriers to early elongation: the promoter-proximal pause site and the +1 nucleosome. It emerges that the first barrier enables loading of elongation factors that are required to overcome the second and subsequent barriers to transcription.

The Unforeseen Diagnosis: Hyperparathyroidism-Jaw Tumour Syndrome Case Report and Review of the Literature

Hypercalcaemia and its systemic sequelae are a relatively common finding amongst patients in the field of endocrinology. Primary hyperparathyroidism, a frequent cause of hypercalcaemia, is often seen among middle-aged female patients, typically resulting from an underlying single-gland adenoma. Although patients may present with symptoms (nephrolithiasis, musculoskeletal discomfort, dehydration, or mood disturbance, to name a few), hypercalcaemia is rather frequently identified incidentally. In younger patients, a familial form of primary hyperparathyroidism must be considered, with a positive diagnosis mandating familial screening. Hyperparathyroidism-jaw tumour syndrome is one such autosomal dominant familial disorder, characterised by a mutation in the cell division cycle 73 (CDC73; also known as HRPT-2) tumour suppressor gene. This disorder is characterised by multiple pleiotropic phenomena, including recurrent primary hyperparathyroidism (and the effects of hypercalcaemia), neoplasms (such as uterine, renal, mandibular, and maxillary), and infertility. A patient not conforming to the classic candidacy for primary hyperparathyroidism requires consideration for a familial cause. Case Description. We present a rare diagnostic entity-hyperparathyroidism-jaw tumour (HPT-JT) syndrome-in a 36-year-old female with recurrent primary hyperparathyroidism, frequent nephrolithiasis, and infertility for 18 years prior to the diagnosis. We aim to promote awareness amongst medical professionals of this rare, but nonetheless essential differential diagnosis through a case report and review of the literature. Conclusion. Medical professionals must avoid diagnostic overshadowing and display a low threshold for genetic testing in younger patients with primary hyperparathyroidism. The importance of proper identification extends beyond the patient to their relatives and offspring.

Rpb5, a subunit shared by eukaryotic RNA polymerases, cooperates with prefoldin-like Bud27/URI

Rpb5 is one of the five common subunits to all eukaryotic RNA polymerases, which is conserved in archaea, but not in bacteria. Among these common subunits, it is the only one that is not interchangeable between yeasts and humans, and accounts for the functional incompatibility of yeast and human subunits. Rpb5 has been proposed to contribute to the gene-specific activation of RNA pol II, notably during the infectious cycle of the hepatitis B virus, and also to participate in general transcription mediated by all eukaryotic RNA pol. The structural analysis of Rpb5 and its interaction with different transcription factors, regulators and DNA, accounts for Rpb5 being necessary to maintain the correct conformation of the shelf module of RNA pol II, which favors the proper organization of the transcription bubble and the clamp closure of the enzyme.

In this work we provide details about subunit Rpb5's structure, conservation and the role it plays in transcription regulation by analyzing the different interactions with several factors, as well as its participation in the assembly of the three RNA pols, in cooperation with prefoldin-like Bud27/URI.

Chromatin-Associated Protein Complexes Link DNA Base J and Transcription Termination in Leishmania

Unlike most other eukaryotes, Leishmania and other trypanosomatid protozoa have largely eschewed transcriptional control of gene expression, relying instead on posttranscriptional regulation of mRNAs derived from polycistronic transcription units (PTUs). In these parasites, a novel modified nucleotide base (β-d-glucopyranosyloxymethyluracil) known as J plays a critical role in ensuring that transcription termination occurs only at the end of each PTU, rather than at the polyadenylation sites of individual genes. To further understand the biology of J-associated processes, we used tandem affinity purification (TAP) tagging and mass spectrometry to reveal proteins that interact with the glucosyltransferase performing the final step in J synthesis. These studies identified four proteins reminiscent of subunits in the PTW/PP1 complex that controls transcription termination in higher eukaryotes. Moreover, bioinformatic analyses identified the DNA-binding subunit of Leishmania PTW/PP1 as a novel J-binding protein (JBP3), which is also part of another complex containing proteins with domains suggestive of a role in chromatin modification/remodeling. Additionally, JBP3 associates (albeit transiently and/or indirectly) with the trypanosomatid equivalent of the PAF1 complex involved in the regulation of transcription in other eukaryotes. The downregulation of JBP3 expression levels in Leishmania resulted in a substantial increase in transcriptional readthrough at the 3′ end of most PTUs. We propose that JBP3 recruits one or more of these complexes to the J-containing regions at the end of PTUs, where they halt the progression of the RNA polymerase. This decoupling of transcription termination from the splicing of individual genes enables the parasites’ unique reliance on polycistronic transcription and posttranscriptional regulation of gene expression.

IMPORTANCELeishmania parasites cause a variety of serious human diseases, with no effective vaccine and emerging resistance to current drug therapy. We have previously shown that a novel DNA base called J is critical for transcription termination at the ends of the polycistronic gene clusters that are a hallmark of Leishmania and related trypanosomatids. Here, we describe a new J-binding protein (JBP3) associated with three different protein complexes that are reminiscent of those involved in the control of transcription in other eukaryotes. However, the parasite complexes have been reprogrammed to regulate transcription and gene expression in trypanosomatids differently than in the mammalian hosts, providing new opportunities to develop novel chemotherapeutic treatments against these important pathogens.

Multiple Endocrine Neoplasia Type 1 (MEN1) Phenocopy Due to a Cell Cycle Division 73 (CDC73) Variant

Multiple endocrine neoplasia type 1 (MEN1) is an autosomal dominant disorder characterized by the combined occurrence of parathyroid tumors, pituitary adenomas, and pancreatic neuroendocrine neoplasms (PNENs). MEN1 is caused by germline MEN1 mutations in > 75% of patients, and the remaining 25% of patients may have mutations in unidentified genes or represent phenocopies with mutations in genes such as cell cycle division 73 (CDC73), the calcium sensing receptor (CASR), and cyclin-dependent kinase inhibitor 1B (CDKN1B), which are associated with the hyperparathyroidism-jaw tumor syndrome, familial hypocalciuric hypercalcemia type 1, and MEN4, respectively. Here, we report a heterozygous c.1138C>T (p.Leu380Phe) CDC73 germline variant in a clinically diagnosed MEN1 patient, based on combined occurrence of primary hyperparathyroidism, acromegaly, and a PNEN. Characterization of the PNEN confirmed it was a neuroendocrine neoplasm as it immuno-stained positively for chromogranin and glucagon. The rare variant p.Leu380Phe occurred in a highly conserved residue, and further analysis using RNA-Scope indicated that it was associated with a significant reduction in CDC73 expression in the PNEN. Previously, CDC73 mutations have been reported to be associated with tumors of the parathyroids, kidneys, uterus, and exocrine pancreas. Thus, our report of a patient with PNEN and somatotrophinoma who had a CDC73 variant, provides further evidence that CDC73 variants may result in a MEN1 phenocopy.

Genotype of CDC73 germline mutation determines risk of parathyroid cancer

Mutation of the CDC73 gene, which encodes parafibromin, has been linked with parathyroid cancer. However, no correlation between genotypes of germline CDC73 mutations and the risk of parathyroid cancer has been known. In this study, subjects with germline CDC73 mutations were identified from the participants of two clinical protocols at National Institutes of Health (Discovery Cohort) and from the literature (Validation Cohort). The relative risk of developing parathyroid cancer was analyzed as a function of CDC73 genotype, and the impact of representative mutations on structure of parafibromin was compared between genotype groups. A total of 419 subjects, 68 in Discovery Cohort and 351 in Validation Cohort, were included. In both cohorts, percentages of CDC73 germline mutations that predicted significant conformational disruption or loss of expression of parafibromin (referred as 'high-impact mutations') were significantly higher among the subjects with parathyroid cancers compared to all other subjects. The Kaplan-Meier analysis showed that high-impact mutations were associated with a 6.6-fold higher risk of parathyroid carcinoma compared to low-impact mutations, despite a similar risk of developing primary hyperparathyroidism between two groups. Disruption of the C-terminal domain (CTD) of parafibromin is directly involved in predisposition to parathyroid carcinoma, since only the mutations impacting this domain were associated with an increased risk of parathyroid carcinoma. Structural analysis revealed that a conserved surface structure in the CTD is universally disrupted by the mutations affecting this domain. In conclusion, high-impact germline CDC73 mutations were found to increase risk of parathyroid carcinoma by disrupting the CTD of parafibromin.

Structure of complete Pol II-DSIF-PAF-SPT6 transcription complex reveals RTF1 allosteric activation

Transcription by RNA polymerase II (Pol II) is carried out by an elongation complex. We previously reported an activated porcine Pol II elongation complex, EC*, encompassing the human elongation factors DSIF, PAF1 complex (PAF) and SPT6. Here we report the cryo-EM structure of the complete EC* that contains RTF1, a dissociable PAF subunit critical for chromatin transcription. The RTF1 Plus3 domain associates with Pol II subunit RPB12 and the phosphorylated C-terminal region of DSIF subunit SPT5. RTF1 also forms four α-helices that extend from the Plus3 domain along the Pol II protrusion and RPB10 to the polymerase funnel. The C-terminal 'fastener' helix retains PAF and is followed by a 'latch' that reaches the end of the bridge helix, a flexible element of the Pol II active site. RTF1 strongly stimulates Pol II elongation, and this requires the latch, possibly suggesting that RTF1 activates transcription allosterically by influencing Pol II translocation.

Challenges in the treatment of parathyroid carcinoma: a case report

INTRODUCTION

Parathyroid carcinoma (PC) is a rare neoplasm with a high rate of recurrence and an indolent course. It is frequently functional, causing nearly 1% of the cases of primary hyperparathyroidism (HPT), and in some cases, it may be complicated by brown tumors, mimicking bone metastases. Synchronous parathyroid and papillary thyroid carcinomas are rare.

CASE REPORT

We present a patient with HPT due to PC, misdiagnosed at first evaluation, which exhibited multiple hypermetabolic lytic lesions in the skeleton, suggesting bone metastases. Their regression after PTH reduction suggested the diagnosis of brown tumors due to severe HPT. Given the persistence of HPT, the patient underwent a number of neck surgeries, and a papillary thyroid microcarcinoma with a nodal metastasis was diagnosed. A genetic test discovered a previously unreported mutation of the CDC73 (HRPT2) gene, codifying for parafibromin and resulting in a premature stop codon (c.580A>Tp.Arg194). Because of the persistence of HPT, cinacalcet therapy was started in order to control hypercalcemia.

CONCLUSION

This is a very unusual patient with a newly discovered variant of the CDC73 gene and a phenotype characterized by recurrent PC, brown tumors, and N1a metastasized thyroid carcinoma. The present case confirms that PC may not exhibit clear malignant properties at first assessment, contributing to inadequate initial surgical treatment. Although infrequently, PC can be associated with papillary thyroid cancer. The diagnosis of brown tumor should be considered in patients with severe HPT and multiple destructive bone lesions mimicking metastases on PET/CT imaging.

RMP promotes the proliferation and radioresistance of esophageal carcinoma

RMP is a RNA polymerase II Subunit RPB-5 associated protein shown to act as an oncogene in several cancer. However, the mechanism of the involvement of RMP in esophageal cancer (EC) remains unclear. We analyzed RMP expression in EC cell lines and EC tissues. The connection between RMP and clinical pathological features of EC was also elucidated. To investigate the role of RMP in EC, We performed CCK-8 assay to evaluate cell proliferation, and Annexin V/PI double-staining to evaluate cell apoptosis. Effect of RMP on tumor progression in nude mouse models was assessed by measurement of volume and weight of tumors. Expression of RMP, CEA and CA199 in vivo were measured by Inmunohistochemical staining. First of all, our study showed that RMP was highly expressed in EC cell lines (compared with normal cells) and tumor tissues (compare with corresponding normal tissues). Then, we found that RMP was bound up with the status of nodal and T stage which indicating that RMP may be related to the growth and malignant degree of EC. Moreover upregulation of RMP could contribute to tumor growth in vitro and vivo. In addition, the results also showed that overexpression of RMP could significantly reduce the susceptibility to radiotherapy. Taken together, all these further suggested that RMP would play a chance-promoting in EC which may provide us a powerful goal for gene targeting treatment of esophageal cancer.

Characterization of a novel CDC73 gene mutation in a hyperparathyrodism-jaw tumor patient affected by parathyroid carcinoma in the absence of somatic loss of heterozygosity

Hyperparathyrodism-jaw tumor (HPT-JT) syndrome is an autosomal dominant disorder. Loss of function of the cell division cycle protein 73 homolog (CDC73) gene is responsible for the syndrome. This gene encodes an ubiquitously expressed 531 amino acid protein, parafibromin, that acts as a tumor suppressor. Loss of heterozygosity (LOH) of the CDC73 locus in many HPT-JT associated parathyroid tumors from patients with germline mutation is in accordance with Knudson's "two-hit" model for hereditary cancer. A 41-year-old man with mandible ossifying fibroma suffered from severe hypercalcemia due to parathyroid carcinoma (PC). Genetic analysis was performed to evaluate germinal and somatic CDC73 gene mutation as well as real-time qRT-PCR to quantify CDC73 mRNA, miR-155 and miR-664 expression levels. Immunohistochemistry and Western blotting (WB) assay were carried out to evaluate parafibromin protein expression. A novel heterozygous nonsense mutation, c.191-192 delT, was identified in the CDC73 gene. No CDC73 LOH was found in PC tissue, nor any differences in expression levels for CDC73 gene, miR-155 and miR-664 between PC and parathyroid adenoma control tissues. On the contrary, both immunohistochemistry and WB assay showed an approximate 90% reduction of parafibromin protein expression in PC. In conclusion, this study describes a novel germinal mutation, c.191-192 delT, in the CDC73 gene. Despite normal CDC73 gene expression, we found a significant decrease in parafibromin. We hypothesize that a gene silencing mechanism, possibly induced by microRNA, could play a role in determining somatic post-transcriptional inactivation of the wild type CDC73 allele.

Clinical Features, Treatment, and Surveillance of Hyperparathyroidism-Jaw Tumor Syndrome: An Up-to-Date and Review of the Literature

Hyperparathyroidism-jaw tumor (HPT-JT) syndrome is an autosomal dominant disorder characterized by parathyroid tumors in association with fibro-osseous jaw tumors and uterine and renal lesions. HPT-JT syndrome is caused by germline mutations of the cell division cycle 73 (CDC73) gene that encodes the parafibromin, a 531-amino acid protein with antiproliferative activity. Primary hyperparathyroidism is the main finding of HPT-JT syndrome, usually caused by a single-gland parathyroid involvement (80% of cases), at variance with other variants of hereditary hyperparathyroidism, in which a multiglandular involvement is more frequent. Moreover, parathyroid carcinoma may occur in approximately 20% of cases. Surgery is the treatment of choice for primary hyperparathyroidism, but the extent of surgery remains controversial, varying between bilateral neck and focused exploration, with subtotal or limited parathyroidectomy. Recently, more limited approaches and parathyroid excisions have been suggested in order to decrease the risk of permanent hypoparathyroidism, the main surgical morbidity following more extensive surgical approaches. Ossifying fibromas of the mandible or maxilla may present only in a minority of cases and, even if benign, they should be surgically treated to avoid tumor growth and subsequent functional limitations. Benign and malignant uterine involvement (including leiomyomas, endometrial hyperplasia, adenomyosis, multiple adenomyomatous polyps, and adenosarcomas) is the second most common clinical feature of the syndrome, affecting more than 50% of CDC73-carrier women. Genetic testing should be performed in all family members of affected individuals, in young patients undergoing surgery for primary hyperparathyroidism, or in presence of other associated tumors, allowing early diagnosis and prompt treatment with more tailored surgery. Moreover, CDC73 mutation carriers should be also periodically screened for primary hyperparathyroidism and the other associated tumors. The present review was aimed to summarize the main clinical features of HPT-JT syndrome, focusing on genetic screening and surgical treatment, and to revise the available literature.

Paf1 and Ctr9 subcomplex formation is essential for Paf1 complex assembly and functional regulation

The evolutionarily conserved multifunctional polymerase-associated factor 1 (Paf1) complex (Paf1C), which is composed of at least five subunits (Paf1, Leo1, Ctr9, Cdc73, and Rtf1), plays vital roles in gene regulation and has connections to development and human diseases. Here, we report two structures of each of the human and yeast Ctr9/Paf1 subcomplexes, which assemble into heterodimers with very similar conformations, revealing an interface between the tetratricopeptide repeat module in Ctr9 and Paf1. The structure of the Ctr9/Paf1 subcomplex may provide mechanistic explanations for disease-associated mutations in human PAF1 and CTR9. Our study reveals that the formation of the Ctr9/Paf1 heterodimer is required for the assembly of yeast Paf1C, and is essential for yeast viability. In addition, disruption of the interaction between Paf1 and Ctr9 greatly affects the level of histone H3 methylation in vivo. Collectively, our results shed light on Paf1C assembly and functional regulation.

Structure of activated transcription complex Pol II-DSIF-PAF-SPT6

Gene regulation involves activation of RNA polymerase II (Pol II) that is paused and bound by the protein complexes DRB sensitivity-inducing factor (DSIF) and negative elongation factor (NELF). Here we show that formation of an activated Pol II elongation complex in vitro requires the kinase function of the positive transcription elongation factor b (P-TEFb) and the elongation factors PAF1 complex (PAF) and SPT6. The cryo-EM structure of an activated elongation complex of Sus scrofa Pol II and Homo sapiens DSIF, PAF and SPT6 was determined at 3.1 Å resolution and compared to the structure of the paused elongation complex formed by Pol II, DSIF and NELF. PAF displaces NELF from the Pol II funnel for pause release. P-TEFb phosphorylates the Pol II linker to the C-terminal domain. SPT6 binds to the phosphorylated C-terminal-domain linker and opens the RNA clamp formed by DSIF. These results provide the molecular basis for Pol II pause release and elongation activation.

Immunohistochemistry in Diagnostic Parathyroid Pathology

Pathologists are usually readily able to diagnose parathyroid tissues and diseases, particularly when they have knowledge of the clinical information, laboratory findings, and radiographic imaging studies. However, the identification of parathyroid tissue or lesions can be difficult in small biopsies, ectopic locations, supranumerary glands, and in some oxyphil/oncocytic lesions. Widely available immunohistochemical studies such as chromogranin-A, synaptophysin, keratin, parathyroid hormone, thyroglobulin, and thyroid transcription factor-1 can help in difficult cases. One of the most difficult diagnostic aspects faced by the pathologist in evaluating parathyroid is distinguishing between parathyroid adenoma, particularly atypical adenoma, and parathyroid carcinoma. Many markers have and continue to be evaluated for diagnostic utility, and are even beginning to be studied for prognostic utility. Single immunohistochemical markers such as parafibromin and Ki-67 are among the most studied and most utilized, but many additional markers have and continue to be evaluated such as galectin-3, PGP9.5, Rb, bcl2, p27, hTERT, mdm2, and APC. Although not widely available in many laboratories, a panel of immunohistochemical markers may prove most useful as an adjunct in the evaluation of challenging parathyroid tumors.

PAF1 complex interactions with SETDB1 mediate promoter H3K9 methylation and transcriptional repression of Hoxa9 and Meis1 in acute myeloid leukemia

The Polymerase Associated Factor 1 complex (PAF1c) is an epigenetic co-modifying complex that directly contacts RNA polymerase II (RNAPII) and several epigenetic regulating proteins. Mutations, overexpression and loss of expression of subunits of the PAF1c are observed in various forms of cancer suggesting proper regulation is needed for cellular development. However, the biochemical interactions with the PAF1c that allow dynamic gene regulation are unclear. We and others have shown that the PAF1c makes a direct interaction with MLL fusion proteins, which are potent oncogenic drivers of acute myeloid leukemia (AML). This interaction is critical for the maintenance of MLL translocation driven AML by targeting MLL fusion proteins to the target genes Meis1 and Hoxa9. Here, we use a proteomics approach to identify protein-protein interactions with the PAF1c subunit CDC73 that regulate the function of the PAF1c. We identified a novel interaction with a histone H3 lysine 9 (H3K9) methyltransferase protein, SETDB1. This interaction is stabilized with a mutant CDC73 that is incapable of supporting AML cell growth. Importantly, transcription of Meis1 and Hoxa9 is reduced and promoter H3K9 trimethylation (H3K9me3) increased by overexpression of SETDB1 or stabilization of the PAF1c-SETDB1 interaction in AML cells. These findings were corroborated in human AML patients where increased SETDB1 expression was associated with reduced HOXA9 and MEIS1. To our knowledge, this is the first proteomics approach to search for CDC73 protein-protein interactions in AML, and demonstrates that the PAF1c may play a role in H3K9me3-mediated transcriptional repression in AML.

Large deletion at the CDC73 gene locus and search for predictive markers of the presence of a CDC73 genetic lesion

The Hyperparathyroidism with Jaw-Tumours syndrome is caused by mutations of the CDC73 gene: it has been suggested that early onset of the disease and high Ca²⁺ levels may predict the presence of a CDC73 mutation. We searched for large deletions at the CDC73 locus in patients with: HPT-JT (nr 2), atypical adenoma (nr 7) or sporadic parathyroid carcinoma (nr 11) with a specific MLPA and qRT-PCR assays applied on DNA extracted from whole blood. A Medline search in database for all the papers reporting a CDC73 gene mutation, clinical/histological diagnosis, age at onset, Ca²⁺, PTH levels for familial/sporadic cases was conducted with the aim to possibly identify biochemical/clinical markers predictive, in first diagnosis, of the presence of a CDC73 gene mutation. A novel genomic deletion of the first 10 exons of the CDC73 gene was found in a 3-generation HPT-JT family, confirmed by SNP array analysis. A classification tree built on the published data, showed the highest probability of having a CDC73 mutation in subjects with age at the onset < 41.5 years (44/47 subjects, 93.6%, had the mutation). Whereas the lowest probability was found in subjects with age at the onset ≥ 41.5 years and Ca²⁺ levels <13.96 mg/dL (7/20 subjects, 35.0%, had the mutation, odds ratio = 27.1, p < 0.001). We report a novel large genomic CDC73 gene deletion identified in an Italian HPT-JT family. Age at onset < 41.5 ys and Ca²⁺ > 13.96 mg/dL are predictive for the presence of a CDC73 genetic lesion.

Rpb5, a subunit shared by eukaryotic RNA polymerases, cooperates with prefoldin-like Bud27/URI

Rpb5 is one of the five common subunits to all eukaryotic RNA polymerases, which is conserved in archaea, but not in bacteria. Among these common subunits, it is the only one that is not interchangeable between yeasts and humans, and accounts for the functional incompatibility of yeast and human subunits. Rpb5 has been proposed to contribute to the gene-specific activation of RNA pol II, notably during the infectious cycle of the hepatitis B virus, and also to participate in general transcription mediated by all eukaryotic RNA pol. The structural analysis of Rpb5 and its interaction with different transcription factors, regulators and DNA, accounts for Rpb5 being necessary to maintain the correct conformation of the shelf module of RNA pol II, which favors the proper organization of the transcription bubble and the clamp closure of the enzyme. In this work we provide details about subunit Rpb5's structure, conservation and the role it plays in transcription regulation by analyzing the different interactions with several factors, as well as its participation in the assembly of the three RNA pols, in cooperation with prefoldin-like Bud27/URI.

Transcriptional Co-activator Functions of YAP and TAZ Are Inversely Regulated by Tyrosine Phosphorylation Status of Parafibromin

YAP and TAZ, the Hippo signal-regulated transcriptional co-activators, play crucial roles in morphogenesis and organogenesis. Here we report that the YAP/TAZ activities are stimulated upon complex formation with Parafibromin, which undergoes tyrosine phosphorylation and dephosphorylation by kinases such as PTK6 and phosphatases such as SHP2, respectively. Furthermore, TAZ and the Wnt effector β-catenin interact cooperatively with tyrosine-dephosphorylated Parafibromin, which synergistically stimulates the co-activator functions of TAZ and β-catenin. On the other hand, YAP is selectively activated through binding with tyrosine-phosphorylated Parafibromin, which does not interact with β-catenin and thus cannot co-activate YAP and β-catenin. These findings indicate that Parafibromin inversely regulates the activities of YAP and TAZ depending on its tyrosine phosphorylation status. They also suggest that YAP and TAZ exert their redundant and non-redundant biological actions through mutually exclusive interaction with Parafibromin, which is regulated by a balance of kinase and phosphatase activities toward Parafibromin.

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YAP and TAZ co-activators bind to the nuclear tyrosine phosphoprotein Parafibromin

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TAZ is functionally activated through binding with dephosphorylated Parafibromin

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YAP activity is stimulated upon binding with tyrosine-phosphorylated Parafibromin

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Dephosphorylated Parafibromin co-stimulates TAZ and β-catenin via complex formation

Role of the Unconventional Prefoldin Proteins URI and UXT in Transcription Regulation

The Unconventional prefoldin RPB5 interacting protein (URI), also known as RPB5-Mediating Protein (RMP) has been shown to play several regulatory roles in different cellular compartments including the mitochondria, as a phosphatase binding protein; in the cytoplasm, as a chaperone-like protein; and in the nucleus, as a transcriptional regulator through binding to RPB5 and RNA polymerase II (polII). This chapter focuses on the role URI plays in transcriptional regulation in the prostate cell. In prostate cells, URI is tightly bound to another prefoldin-like protein called UXT, a known androgen receptor (AR) cofactor. Part of a multiprotein complex, URI and UXT act as transcriptional repressors, and URI regulates KAP1 through PP2A phosphatase activity. The discovery of the interaction of URI and UXT with KAP1, AR, and PP2A, as well as the numerous interactions between URI and components of the R2TP/prefoldin-like complex, RPB5, and nuclear proteins involved in DNA damage response, chromatin remodeling and gene transcription, reveal a pleiotropic effect of the URI/UXT complex on nuclear processes. The mechanisms by which URI/UXT affect transcription, chromatin structure and regulation, and genome stability, remain to be elucidated but will be of fundamental importance considering the many processes affected by alterations of URI/UXT and other prefoldins and prefoldin-like proteins.

Roles and Functions of the Unconventional Prefoldin URI

Almost 15 years ago, the URI prefoldin-like complex was discovered by Krek and colleagues in immunoprecipitation experiments conducted in mammalian cells with the aim of identifying new binding partners of the E3 ubiquitin-protein ligase S-phase kinase-associated protein 2 (SKP2) (Gstaiger et al. Science 302(5648):1208-1212, 2003). The URI prefoldin-like complex is a heterohexameric chaperone complex comprising two α and four β subunits (α2β4). The α subunits are URI and STAP1, while the β subunits are PFDN2, PFDN6, and PFDN4r, one of which is probably present in duplicate. Elucidating the roles and functions of these components in vitro and in vivo will help to clarify the mechanistic behavior of what appears to be a remarkably important cellular machine.

Molecular genetics of syndromic and non-syndromic forms of parathyroid carcinoma

Parathyroid carcinoma (PC) may occur as part of a complex hereditary syndrome or an isolated (i.e., non-syndromic) non-hereditary (i.e., sporadic) endocrinopathy. Studies of hereditary and syndromic forms of PC, which include the hyperparathyroidism-jaw tumor syndrome (HPT-JT), multiple endocrine neoplasia types 1 and 2 (MEN1 and MEN2), and familial isolated primary hyperparathyroidism (FIHP), have revealed some genetic mechanisms underlying PC. Thus, cell division cycle 73 (CDC73) germline mutations cause HPT-JT, and CDC73 mutations occur in 70% of sporadic PC, but in only ∼2% of parathyroid adenomas. Moreover, CDC73 germline mutations occur in 20%-40% of patients with sporadic PC and may reveal unrecognized HPT-JT. This indicates that CDC73 mutations are major driver mutations in the etiology of PCs. However, there is no genotype-phenotype correlation and some CDC73 mutations (e.g., c.679_680insAG) have been reported in patients with sporadic PC, HPT-JT, or FIHP. Other genes involved in sporadic PC include germline MEN1 and rearranged during transfection (RET) mutations and somatic alterations of the retinoblastoma 1 (RB1) and tumor protein P53 (TP53) genes, as well as epigenetic modifications including DNA methylation and histone modifications, and microRNA misregulation. This review summarizes the genetics and epigenetics of the familial syndromic and non-syndromic (sporadic) forms of PC.

The clinicopathological and prognostic significances of CDC73 expression in cancers: a bioinformatics analysis

CDC73 interacts with human PAF1 complex, histone methyltransferase complex and RNA polymerase II for transcription elongation and 3’ end processing. Its down-regulated expression was immunohistochemically detected in gastric, colorectal, ovarian and head and neck cancers, and positively correlated with aggressive behaviors and unfavorable prognosis of malignancies. We performed a bioinformatics analysis by using Oncomine, TCGA and KM plotter databases. It was found that CDC73 mRNA was overexpressed in gastric, lung, breast and ovarian cancers, even stratified by histological subtypes (p<0.05). CDC73 mRNA expression was stronger in gastric intestinal- than diffuse-type carcinomas (p<0.05), and positively correlated with distant metastasis and TNM staging of lung cancer (p<0.05). CDC73 mRNA expression was positively related to both overall and progression-free survival rates of the patients with gastric cancer, even stratified by gender, lymph node involvement, or treatment (p<0.05), while versa for breast cancer (p<0.05). The prognostic significance of CDC73 mRNA was dependent on the datasets and pathological grouping in lung and ovarian cancers. These findings indicated the CDC73 mRNA overexpression was positively linked to carcinogenesis. It is cautious to employ CDC73 mRNA to evaluate the clinicopathological behaviors and prognosis of cancers.

Large intragenic deletion of CDC73 (exons 4-10) in a three-generation hyperparathyroidism-jaw tumor (HPT-JT) syndrome family

Background

Inactivating mutations of CDC73 cause Hyperparathyroidism-Jaw Tumour syndrome (HPT-JT), Familial Isolated Hyperparathyroidism (FIHP) and sporadic parathyroid carcinoma. We conducted CDC73 mutation analysis in an HPT-JT family and confirm carrier status of the proband’s daughter.

Methods

The proband had primary hyperparathyroidism (parathyroid carcinoma) and uterine leiomyomata. Her father and daughter had hyperparathyroidism (parathyroid adenoma) but no other manifestations of HPT-JT. CDC73 mutation analysis (sequencing of all 17 exons) and whole-genome copy number variation (CNV) analysis was done on leukocyte DNA of the three affecteds as well as the proband’s unaffected sister.

Results

A novel deletion of exons 4 to 10 of CDC73 was detected by CNV analysis in the three affecteds. A novel insertion in the 5’UTR (c.-4_-11insG) that co-segregated with the deletion was identified. By in vitro assay the 5’UTR insertion was shown to significantly impair the expression of the parafibromin protein. Screening for the mutated CDC73 confirmed carrier status in the proband’s daughter and the biochemistry and ultrasonography led to pre-emptive surgery and resolution of the hyperparathyroidism.

Conclusions

A novel gross deletion mutation in CDC73 was identified in a three-generation HPT-JT family emphasizing the importance of including screening for large deletions in the molecular diagnostic protocol.

Electronic supplementary material

The online version of this article (doi:10.1186/s12881-017-0445-0) contains supplementary material, which is available to authorized users.

Osteoblast-specific deletion of Hrpt2/Cdc73 results in high bone mass and increased bone turnover

Inactivating mutations that lead to loss of heterozygosity within the HRPT2/Cdc73 gene are directly linked to the development of primary hyperparathyroidism, parathyroid adenomas, and ossifying fibromas of the jaw (HPT-JT). The protein product of the Cdc73 gene, parafibromin, is a core member of the polymerase-associated factors (PAF) complex, which coordinates epigenetic modifiers and transcriptional machinery to control gene expression. We conditionally deleted Cdc73 within mesenchymal progenitors or within mature osteoblasts and osteocytes to determine the consequences of parafibromin loss within the mesenchymal lineage. Homozygous deletion of Cdc73 via the Dermo1-Cre driver resulted in embryos which lacked mesenchymal organ development of internal organs, including the heart and fetal liver. Immunohistochemical detection of cleaved caspase-3 revealed extensive apoptosis within the progenitor pools of developing organs. Unexpectedly, when Cdc73 was homozygously deleted within mature osteoblasts and osteocytes (via the Ocn-Cre driver), the mice had a normal life span but increased cortical and trabecular bone. OCN-Cre;Cdc73^flox/flox bones displayed large cortical pores actively undergoing bone remodeling. Additionally the cortical bone of OCN-Cre;Cdc73^flox/flox femurs contained osteocytes with marked amounts of cytoplasmic RNA and a high rate of apoptosis. Transcriptional analysis via RNA-seq within OCN-Cre;Cdc73^flox/flox osteoblasts showed that loss of Cdc73 led to a derepression of osteoblast-specific genes, specifically those for collagen and other bone matrix proteins. These results aid in our understanding of the role parafibromin plays within transcriptional regulation, terminal differentiation, and bone homeostasis.

Mice deleted for cell division cycle 73 gene develop parathyroid and uterine tumours: model for the hyperparathyroidism-jaw tumour syndrome

The hyperparathyroidism-jaw tumour (HPT-JT) syndrome is an autosomal dominant disorder characterized by occurrence of parathyroid tumours, often atypical adenomas and carcinomas, ossifying jaw fibromas, renal tumours and uterine benign and malignant neoplasms. HPT-JT is caused by mutations of the cell division cycle 73 (CDC73) gene, located on chromosome 1q31.2 and encodes a 531 amino acid protein, parafibromin. To facilitate in vivo studies of Cdc73 in tumourigenesis we generated conventional (Cdc73^+/-) and conditional parathyroid-specific (Cdc73^+/L/PTH-Cre and Cdc73^L/L/PTH-Cre) mouse models. Mice were aged to 18-21 months and studied for survival, tumour development and proliferation, and serum biochemistry, and compared to age-matched wild-type (Cdc73^+/+ and Cdc73^+/+/PTH-Cre) littermates. Survival of Cdc73^+/- mice, when compared to Cdc73^+/+ mice was reduced (Cdc73^+/-=80%; Cdc73^+/+=90% at 18 months of age, P<0.05). Cdc73^+/-, Cdc73^+/L/PTH-Cre and Cdc73^L/L/PTH-Cre mice developed parathyroid tumours, which had nuclear pleomorphism, fibrous septation and increased galectin-3 expression, consistent with atypical parathyroid adenomas, from 9 months of age. Parathyroid tumours in Cdc73^+/-, Cdc73^+/L/PTH-Cre and Cdc73^L/L/PTH-Cre mice had significantly increased proliferation, with rates >fourfold higher than that in parathyroid glands of wild-type littermates (P<0.0001). Cdc73^+/-, Cdc73^+/L/PTH-Cre and Cdc73^L/L/PTH-Cre mice had higher mean serum calcium concentrations than wild-type littermates, and Cdc73^+/- mice also had increased mean serum parathyroid hormone (PTH) concentrations. Parathyroid tumour development, and elevations in serum calcium and PTH, were similar in males and females. Cdc73^+/- mice did not develop bone or renal tumours but female Cdc73^+/- mice, at 18 months of age, had uterine neoplasms comprising squamous metaplasia, adenofibroma and adenomyoma. Uterine neoplasms, myometria and jaw bones of Cdc73^+/- mice had increased proliferation rates that were 2-fold higher than in Cdc73^+/+ mice (P<0.05). Thus, our studies, which have established mouse models for parathyroid tumours and uterine neoplasms that develop in the HPT-JT syndrome, provide in vivo models for future studies of these tumours.

URI Regulates KAP1 Phosphorylation and Transcriptional Repression via PP2A Phosphatase in Prostate Cancer Cells

URI (unconventional prefoldin RPB5 interactor protein) is an unconventional prefoldin, RNA polymerase II interactor that functions as a transcriptional repressor and is part of a larger nuclear protein complex. The components of this complex and the mechanism of transcriptional repression have not been characterized. Here we show that KAP1 (KRAB-associated protein 1) and the protein phosphatase PP2A interact with URI. Mechanistically, we show that KAP1 phosphorylation is decreased following recruitment of PP2A by URI. We functionally characterize the novel URI-KAP1-PP2A complex, demonstrating a role of URI in retrotransposon repression, a key function previously demonstrated for the KAP1-SETDB1 complex. Microarray analysis of annotated transposons revealed a selective increase in the transcription of LINE-1 and L1PA2 retroelements upon knockdown of URI. These data unveil a new nuclear function of URI and identify a novel post-transcriptional regulation of KAP1 protein that may have important implications in reactivation of transposable elements in prostate cancer cells.

Genetics of parathyroid tumours

Primary hyperparathyroidism (PHPT), due to parathyroid tumours, may occur as part of a complex syndrome or as an isolated (nonsyndromic) disorder, and both forms can occur as familial (i.e. hereditary) or nonfamilial (i.e. sporadic) disease. Syndromic PHPT includes multiple endocrine neoplasia (MEN) types 1 to 4 (MEN1 to MEN4) and the hyperparathyroidism-jaw tumour (HPT-JT) syndrome. Syndromic and hereditary PHPT are often associated with multiple parathyroid tumours, in contrast to sporadic PHPT, in which single parathyroid adenomas are more common. In addition, parathyroid carcinomas may occur in ~15% of patients with the HPT-JT syndrome. MEN1 is caused by abnormalities of the MEN1 gene which encodes a tumour suppressor; MEN2 and MEN3 are due to mutations of the rearranged during transfection (RET) proto-oncogene, which encodes a tyrosine kinase receptor; MEN4 is due to mutations of a cyclin-dependent kinase inhibitor (CDNK1B); and HPT-JT is due to mutations of cell division cycle 73 (CDC73), which encodes parafibromin. Nonsyndromic PHPT, which may be hereditary and referred to as familial isolated hyperparathyroidism, may also be due to MEN1, CDC73 or calcium-sensing receptor (CASR) mutations. In addition, ~10% of patients presenting below the age of 45 years with nonsyndromic, sporadic PHPT may have MEN1, CDC73 or CASR mutations, and overall more than 10% of patients with PHPT will have a mutation in one of 11 genes. Genetic testing is available and of value in the clinical setting, as it helps in making the correct diagnosis and planning the management of these complex disorders associated with parathyroid tumours.

Transcription factors that influence RNA polymerases I and II: To what extent is mechanism of action conserved?

In eukaryotic cells, nuclear RNA synthesis is accomplished by at least three unique, multisubunit RNA polymerases. The roles of these enzymes are generally partitioned into the synthesis of the three major classes of RNA: rRNA, mRNA, and tRNA for RNA polymerases I, II, and III respectively. Consistent with their unique cellular roles, each enzyme has a complement of specialized transcription factors and enzymatic properties. However, not all transcription factors have evolved to affect only one eukaryotic RNA polymerase. In fact, many factors have been shown to influence the activities of multiple nuclear RNA polymerases. This review focuses on a subset of these factors, specifically addressing the mechanisms by which these proteins influence RNA polymerases I and II.

Cystic parathyroid glands in MEN1: A rare entity?

Approximately 300 cases of sporadic parathyroid cyst (PCs) have been reported to date. Only two cases have been described in MEN1 so far. Detection by imaging could be challenging, especially in multiglandular primary hyperparathyroidism (HPT) and clinical outcome could be different. During the period 1990-2014, 71 MEN1 patients were operated for primary hyperparathyroidism in our centre. We report three cases of PCs in MEN1 patients affected by HPT, who underwent a total or subtotal parathyroidectomy with transcervical thymectomy. In our series, all three patients had an unsatisfactory postoperative course, at variance with the high percentage (over 90 %) of long-term success in MEN1 patients operated at our centre. One patient affected by cystic degeneration of all the four parathyroid glands reported persistent hypoparathyroidism, despite autografts of parathyroid tissue. For the other two cases, surgery failed to cure hyperparathyroidism, perhaps because of the presence of undetected ectopic parathyroid tissue. In the context of a multiglandular disease such as MEN1 syndrome, PCs seem rare but our experience shows about a 4 % incidence. Furthermore their presence, even in expert hands, could affect the preoperative identification of the parathyroid glands due to the difficult differential diagnosis between PC and other cystic lesions of the neck, and intraoperative detection of the glands as well as the postoperative outcome.

CDC73 gene mutations in sporadic ossifying fibroma of the jaws

Background

The tumor suppressor gene CDC73 was found to be associated with hyperparathyroidism-jaw tumor syndrome (HPT-JT), which is characterized by parathyroid adenoma or carcinoma, ossifying fibroma (OF) of the jaws, and renal and uterine lesions. Mutations in CDC73 have also been frequently detected in sporadic parathyroid carcinomas and renal tumors. However, the prevalence and range of CDC73 mutations in sporadic OFs have not been established.

Methods

We directly sequenced coding and flanking splice junctional regions of CDC73 in 40 cases of sporadic OF of the jaws. We also used immunohistochemistry to detect parafibromin, the protein product of CDC73, in those cases.

Results

Two novel CDC73 mutations were identified in 2 of the 40 cases (5 %). Both were somatic mutations located in exon 1 of the coding region. Strong parafibromin expression was detected in all 40 cases, irrespective of the presence of CDC73 mutations.

Conclusions

Mutations inCDC73 were rare in sporadic OF of the jaws, but may affect the pathogenesis of a small subset of tumors of this type.

Significance of Parafibromin Expression in Laryngeal Squamous Cell Carcinomas

BACKGROUND

Parafibromin is a product of the tumor suppressor gene that has been studied as a potential indicator of tumor aggressiveness in the parathyroid, breast, colorectum, and stomach. However, the clinical significance and potential function of parafibromin expression in head and neck squamous cell carcinomas remain largely unknown. The aim of this study was to evaluate the expression of parafibromin in laryngeal squamous cell carcinoma (LSCC) and to verify its potential as a biomarker of tumor behavior.

METHODS

Parafibromin expression was evaluated in 30 cases of LSCC using immunohistochemistry. The correlations between parafibromin expression and clinicopathologic parameters were investigated.

RESULTS

Parafibromin expression was positive in 15 cases (50%) and negative in 15 cases (50%). Tumor size and T stage showed a statistically significant inverse relationship with parafibromin expression (p=.028 and p<.001, respectively). Parafibromin expression was not associated with age, sex, lymph node metastasis, tumor differentiation, or tumor location. There was no statistically significant relationship between parafibromin expression and progression-free survival in the patients (p>.05).

CONCLUSIONS

Our results indicate that the downregulation or loss of parafibromin expression can be employed as a novel marker of tumor progression or aggressiveness in LSCC.

Update on parathyroid carcinoma

INTRODUCTION

Parathyroid carcinoma (PC) is a rare endocrine disorder, commonly causing severe primary hyperparathyroidism (PHPT). PC is mainly a sporadic disease, but it may occur in familial PHPT. Patients with PC usually present markedly elevated serum calcium and PTH. The clinical features are mostly due to the effects of the excessive secretion of PTH rather than to the spread of tumor. At times, the diagnosis can be difficult.

PURPOSE

The aim of this work is to review the available data on PC, and focus its molecular pathogenesis and the clinical utility of CDC73 genetic testing and immunostaining of its product, parafibromin. The pathological diagnosis of PC is restricted to lesions showing unequivocal growth into adjacent tissues or metastasis. Inactivating mutations of the cell division cycle 73 (CDC73) gene have been identified in up to 70 % of apparently sporadic PC and in one-third are germline. Loss of parafibromin immunostaining has been shown in most PC. The association of CDC73 mutations and loss of parafibromin predicts a worse clinical outcome and a lower overall 5- and 10-year survival.

CONCLUSIONS

The treatment of choice is the en bloc resection of the tumor. The course of PC is variable; most patients have local recurrences or distant metastases and die from unmanageable hypercalcemia.

An adolescent case of familial hyperparathyroidism with a germline frameshift mutation of the CDC73 gene

A 13-yr-old boy who complained of persistent nausea, vomiting and weight loss had hypercalcemia and an elevated intact PTH level. Computed tomography confirmed two tumors in the thyroid gland. The tumors were surgically removed and pathologically confirmed as parathyroid adenoma. Because his maternal aunt and grandmother both had histories of parathyroid tumors, genetic investigation was undertaken for him, and a germline frameshift mutation of the CDC73 gene was identified. CDC73 gene analysis should be done on individuals who are at risk of familial hyperparathyroidism, including those who are asymptomatic, and they should be followed for potential primary hyperparathyroidism and associated disorders including resultant parathyroid carcinoma.