Characterization of the gene for dbpA, a family member of the nucleic-acid-binding proteins containing a cold-shock domain

DNA-Binding Protein A Is Actively Secreted in a Calcium-and Inflammasome-Dependent Manner and Negatively Influences Tubular Cell Survival

DNA-binding protein A (DbpA) belongs to the Y-box family of cold shock domain (CSD) proteins that bind RNA/DNA and exert intracellular functions in cell stress, proliferation, and differentiation. Given the pattern of DbpA staining in inflammatory glomerular diseases, without adherence to cell boundaries, we hypothesized extracellular protein occurrence and specific functions. Lipopolysaccharide and ionomycin induce DbpA expression and secretion from melanoma and mesangial cells. Unlike its homologue Y-box-binding protein 1 (YB-1), DbpA secretion requires inflammasome activation, as secretion is blocked upon the addition of a NOD-like receptor protein-3 (NLRP3) inhibitor. The addition of recombinant DbpA enhances melanoma cell proliferation, migration, and competes with tumor necrosis factor (TNF) binding to its receptor (TNFR1). In TNF-induced cell death assays, rDbpA initially blocks TNF-induced apoptosis, whereas at later time points (>24 h), cells are more prone to die. Given that CSD proteins YB-1 and DbpA fulfill the criteria of alarmins, we propose that their release signals an inherent danger to the host. Some data hint at an extracellular complex formation at a ratio of 10:1 (DbpA:YB-1) of both proteins.

Cold Shock Domain Protein DbpA Orchestrates Tubular Cell Damage and Interstitial Fibrosis in Inflammatory Kidney Disease

DNA-binding protein A (DbpA) belongs to the Y-box family of cold shock domain proteins that exert transcriptional and translational activities in the cell via their ability to bind and regulate mRNA. To investigate the role of DbpA in kidney disease, we utilized the murine unilateral ureter obstruction (UUO) model, which recapitulates many features of obstructive nephropathy seen in humans. We observed that DbpA protein expression is induced within the renal interstitium following disease induction. Compared with wild-type animals, obstructed kidneys from Ybx3-deficient mice are protected from tissue injury, with a significant reduction in the number of infiltrating immune cells as well as in extracellular matrix deposition. RNAseq data from UUO kidneys show that Ybx3 is expressed by activated fibroblasts, which reside within the renal interstitium. Our data support a role for DbpA in orchestrating renal fibrosis and suggest that strategies targeting DbpA may be a therapeutic option to slow disease progression.

A novel 27-bp indel in the intron region of the YBX3 gene is associated with growth traits in chickens

1. The DNA/RNA binding protein YBX3 is associated with gene transcription, DNA repair, and the progression of various diseases and is highly conserved from bacteria to humans.2. The following experiment found a 27-bp insertion/deletion polymorphism in the intron region of the YBX3 gene through resequencing. In cross-designed, F₂ resource groups, the indel was significantly associated with broiler weight and body size at 0, 2, 4, 6, 8, 10 and 12 weeks of age and several other traits (semi evisceration weight (SEW), evisceration weight (EW), semi evisceration rate (SER), evisceration rate (ER), head weight (HW), claw weight (CLW), wing weight (DWW), gizzard weight (GW), pancreas weight (PW), chest muscle weight (CMW), leg weight (LW), leg muscle weight (LMW), shedding weight (SW), carcass weight (CW) and pectoral area (PA)) (P<0.05).3. The insertion-insertion (II) genotype was significantly associated with the greatest growth traits and carcass traits, whereas the values associated with the insertion-deletion (ID) genotype were the lowest in the F₂ reciprocal cross chickens.4. The mutation sites were genotyped in 3611 individuals from 13 different chicken breeds and cross-designed F₂ resource groups. The II genotype is the most important in commercial broilers, and the I allele frequency observed in these breeds was relatively high. However, there is still considerable potential in breeding dual-purpose chickens and commercial laying hens.5. The mRNA expression of the YBX3 gene in tissues from different breeds and developmental stages demonstrated that the 27-bp indel may affect the entire development process of poultry by affecting muscle development. These findings are beneficial for elucidating the function of the YBX3 gene and facilitating enhanced reproduction in the chicken industry.

Identification of prognostic and metastasis-related alternative splicing signatures in hepatocellular carcinoma

As the most common neoplasm in digestive system, hepatocellular carcinoma (HCC) is one of the most important leading cause of cancer deaths worldwide. Its high-frequency metastasis and relapse rate lead to the poor survival of HCC patients. However, the mechanism of HCC metastasis is still unclear. Alternative splicing events (ASEs) have a great effect in cancer development, progression and metastasis. We downloaded RNA sequencing and seven types of ASEs data of HCC samples, in order to explore the mechanism of ASEs underlying tumorigenesis and metastasis of HCC. The data were taken from the The Cancer Genome Atlas (TCGA) and TCGASpliceSeq databases. Univariate Cox regression analysis was used to determine a total of 3197 overall survival-related ASEs (OS-SEs). And based on five OS-SEs screened by Lasso regression, we constructed a prediction model with the Area Under Curve of 0.765. With a good reliability of the model, the risk score was also proved to be an independent predictor. Among identified 390 candidate SFs, Y-box protein 3 (YBX3) was significantly correlated with OS and metastasis. Among 177 ASEs, ATP-binding cassette subfamily A member 6 (ABCA6)-43162-AT and PLIN5-46808-AT were identified both associated with OS, bone metastasis and co-expressed with SFs. Then we identified primary bile acid biosynthesis as survival-related (KEGG) pathway by Gene Set Variation Analysis (GSVA) and univariate regression analysis, which was correlated with ABCA6-43162-AT and PLIN5-46808-AT. Finally, we proposed that ABCA6-43162-AT and PLIN5-46808-AT may contribute to HCC poor prognosis and metastasis under the regulation of aberrant YBX3 through the pathway of primary bile acid biosynthesis.

YBX3 Mediates the Metastasis of Nasopharyngeal Carcinoma via PI3K/AKT Signaling

The metastasis of nasopharyngeal carcinoma (NPC) is a complex process associated with oncogenic dysfunction, the deciphering of which remains a challenge and requires more in-depth studies. Y-box protein 3 (YBX3) is a DNA/RNA binding protein associated with gene transcription, DNA repair, and the progression of various diseases. However, whether and how YBX3 affects the metastasis of NPC remains unknown. Thus, in this study, we aimed to investigate the role of YBX3 in the metastasis of NPC and determine its underlying mechanism. Interestingly, it was found that the expression of YBX3, which was associated with NPC metastasis, was upregulated in the clinical NPC tissues and cell lines. Moreover, we found that knockdown of YBX3 expression by lentivirus shRNA significantly suppressed NPC cells migration in vitro and metastasis in vivo. Mechanistically, RNA sequencing results suggested that the genes regulated by YBX3 were significantly enriched in cell adhesion molecules, cAMP signaling pathway, calcium signaling pathway, focal adhesion, PI3K/AKT signaling pathway, Ras signaling pathway, Rap1 signaling pathway, NF-κB signaling pathway, and Chemokine signaling pathway. Of these, PI3K/AKT signaling pathway contained the most genes. Accordingly, YBX3 knockdown decreased the activation of PI3K/AKT signaling pathway, thereby inhibit epithelial-to-mesenchymal transition (EMT) and MMP1. These results have demonstrated that YBX3 are involved in the metastasis of NPC through regulating PI3K/AKT signaling pathway, and serve as a potential therapeutic target for patients with NPC.

Antimicrobial peptide LL-37 promotes the proliferation and invasion of skin squamous cell carcinoma by upregulating DNA-binding protein A

The antimicrobial peptide LL-37 not only contributes to the host defence against microbial invasion but also regulates immune activity, angiogenesis and cell proliferation. Studies have shown that LL-37 participates in the development of a variety of tumours, such as lung cancer, ovarian cancer, breast cancer and melanoma. However, the role of LL-37 in the development of skin squamous cell carcinoma (SCC) is not clear. The present study used immunohistochemistry to confirm that the expression of human DNA-binding protein A (dbpA) was increased in SCC tissues. After stimulating SCC A341 cells, LL-37 was shown promote the proliferation, migration and invasion of these malignant cells. LL-37 also promoted the upregulation of dbpA mRNA and protein expression. In addition, after using small interfering RNA to silence the normal dbpA expression in these malignant cells, the proliferation and invasion of the tumor cells were significantly reduced. When the NF-κB inhibitor PDTC was used to inhibit the process of LL-37-stimulated cells, it was found that the original upregulated expression of dbpA was downregulated. Overall, the present demonstrated that by upregulating the expression of dbpA, LL-37 can promote the proliferation and invasion of tumour cells, and that this process depends on the NF-κB signalling pathway.

RNAi-mediated downregulation of DNA binding protein A inhibits tumorigenesis in colorectal cancer

DNA binding protein A (dbpA) belongs to the Y-box binding protein family and has been reported to play an important role in carcinogenesis. Our previous study demonstrated that the knockdown of dbpA in gastric cancer cells inhibited cell proliferation by modulating the cell cycle. However, the role of dbpA in human colorectal cancer (CRC) remains unclear. In this study, immunohistochemical (IHC) staining and clinicopathological parameter analysis were employed to detect dbpA expression in 44 paired CRC samples and 7 CRC cell lines. Lentivirus-mediated short hairpin RNA (shRNA) was used to silence dbpA, and the effects of dbpA knockdown on cell proliferation were determined by MTT assay, colony formation assay and flow cytometry. Furthermore, a xenograft model was established to observe tumor growth in vivo. Functional analysis indicated that dbpA was overexpressed in the CRC tissues and cell lines, and a high dbpA expression was associated with the depth of invasion (p<0.001), the degree of differentiation (p<0.001), lymphatic metastasis (p<0.001) and vessel invasion (p<0.001). The suppression of dbpA expression resulted in decreased cell proliferation in vitro and tumor growth in vivo, and it induced cell cycle arrest and promoted the apoptosis of the CRC cells. As a whole, our findings illustrate the crucial role of dbpA in colorectal tumorigenesis. Thus, dbpA may be used as a novel and potent therapeutic target in CRC.

Cold Shock Proteins Mediate GN with Mesangioproliferation

DNA binding protein A (DbpA) is a member of the human cold shock domain-containing protein superfamily, with known functions in cell proliferation, differentiation, and stress responses. DbpA mediates tight junction-associated activities in tubular epithelial cells, but the function of DbpA in mesangial cells is unknown. Here, we found DbpA protein expression restricted to vascular smooth muscle cells in healthy human kidney tissue but profound induction of DbpA protein expression within the glomerular mesangial compartment in mesangioproliferative nephritis. In vitro, depletion or overexpression of DbpA using lentiviral constructs led to inhibition or promotion, respectively, of mesangial cell proliferation. Because platelet-derived growth factor B (PDGF-B) signaling has a pivotal role in mesangial cell proliferation, we examined the regulatory effect of PDGF-B on DbpA. In vitro studies of human and rat mesangial cells confirmed a stimulatory effect of PDGF-B on DbpA transcript numbers and protein levels. Additional in vivo investigations showed DbpA upregulation in experimental rat anti-Thy1.1 nephritis and murine mesangioproliferative nephritis models. To interfere with PDGF-B signaling, we injected nephritic rats with PDGF-B neutralizing aptamers or the MEK/ERK inhibitor U0126. Both interventions markedly decreased DbpA protein expression. Conversely, continuous PDGF-B infusion in healthy rats induced DbpA expression predominantly within the mesangial compartment. Taken together, these results indicate that DbpA is a novel target of PDGF-B signaling and a key mediator of mesangial cell proliferation.

Alterations in the interactome of serine/threonine protein phosphatase type-1 in atrial fibrillation patients

BACKGROUND

Atrial fibrillation (AF) is the most common sustained cardiac arrhythmia, yet current pharmacological treatments are limited. Serine/threonine protein phosphatase type-1 (PP1), a major phosphatase in the heart, consists of a catalytic subunit (PP1c) and a large set of regulatory (R)-subunits that confer localization and substrate specificity to the holoenzyme. Previous studies suggest that PP1 is dysregulated in AF, but the mechanisms are unknown.

OBJECTIVES

The purpose of this study was to test the hypothesis that PP1 is dysregulated in paroxysmal atrial fibrillation (PAF) at the level of its R-subunits.

METHODS

Cardiac lysates were coimmunoprecipitated with anti-PP1c antibody followed by mass spectrometry-based, quantitative profiling of associated R-subunits. Subsequently, label-free quantification (LFQ) was used to evaluate altered R-subunit-PP1c interactions in PAF patients. R-subunits with altered binding to PP1c in PAF were further studied using bioinformatics, Western blotting (WB), immunocytochemistry, and coimmunoprecipitation.

RESULTS

A total of 135 and 78 putative PP1c interactors were captured from mouse and human cardiac lysates, respectively, including many previously unreported interactors with conserved PP1c docking motifs. Increases in binding were found between PP1c and PPP1R7, cold-shock domain protein A (CSDA), and phosphodiesterase type-5A (PDE5A) in PAF patients, with CSDA and PDE5A being novel interactors validated by bioinformatics, immunocytochemistry, and coimmunoprecipitation. WB confirmed that these increases in binding cannot be ascribed to their changes in global protein expression alone.

CONCLUSIONS

Subcellular heterogeneity in PP1 activity and downstream protein phosphorylation in AF may be attributed to alterations in PP1c-R-subunit interactions, which impair PP1 targeting to proteins involved in electrical and Ca(2+) remodeling. This represents a novel concept in AF pathogenesis and may provide more specific drug targets for treating AF.

Differential distribution of Y-box-binding protein 1 and cold shock domain protein A in developing and adult human brain

The two cold shock domain containing proteins, Y-box-binding protein-1 and cold shock domain protein A were immunolocalized in developing and adult human brain. With the exception of a small population of hypothalamic astrocytes, brain Y-box-binding protein-1 was predominantly found in multiple neurons in the mature human CNS, which might be related to its involvement in neurotransmission and other neuron-associated functions. Cold shock domain protein A was typically observed in astrocytes, oligodendrocytes, choroid plexus epithelia and nerve fibers. However, in circumscribed brain regions as hypothalamus, habenula, and cerebellum, this protein was also expressed in neurons. In the prenatal brain, both proteins were found to be abundantly expressed in radial glial cells, neuroblasts and neurons, which might be an anatomical correlate of the proposed roles of both proteins in cell proliferation and differentiation. In addition, Y-box-binding protein-1 was identified in cultured, lipopolysaccharide-stimulated microglial cells, which underscores its putative role as a mediator in immune and inflammatory processes.

Y-box binding protein-1 implicated in translational control of fetal myocardial gene expression after cardiac transplant

Peri-transplant surgical trauma and ischemia/reperfusion injury in accepted murine heterotopic heart grafts has been associated with myofibroblast differentiation, cardiac fibrosis and biomechanical-stress activation of the fetal myocardial smooth muscle α-actin (SMαA) gene. The wound-healing agonists, transforming growth factor β1 and thrombin, are known to coordinate SMαA mRNA transcription and translation in activated myofibroblasts by altering the subcellular localization and mRNA-binding affinity of the Y-box binding protein-1 (YB-1) cold-shock domain (CSD) protein that governs a variety of cellular responses to metabolic stress. YB-1 accumulated in polyribosome-enriched regions of the sarcoplasm proximal to cardiac intercalated discs in accepted heart grafts. YB-1 binding to a purine-rich motif in exon 3 of SMαA mRNA that regulates translational efficiency increased substantially in perfusion-isolated, rod-shaped adult rat cardiomyocytes during phenotypic de-differentiation in the presence of serum-derived growth factors. Cardiomyocyte de-differentiation was accompanied by the loss of a 60 kDa YB-1 variant that was highly expressed in both adult myocardium and freshly isolated myocytes and replacement with the 50 kDa form of YB-1 (p50) typically expressed in myofibroblasts that demonstrated sequence-specific interaction with SMαA mRNA. Accumulation of p50 YB-1 in reprogrammed, de-differentiated myocytes was associated with a 10-fold increase in SMαA protein expression. Endomyocardial biopsies collected from patients up to 14 years after heart transplant showed variable yet coordinately elevated expression of SMαA and p50 YB-1 protein and demonstrable p50 YB-1:SMαA mRNA interaction. The p60 YB-1 variant in human heart graft samples, but neither mouse p60 nor mouse or human p50, reacted with an antibody specific for the phosphoserine 102 modification in the YB-1 CSD. Modulation of YB-1 subcellular compartmentalization and mRNA-binding activity may be linked with reprogramming of contractile protein gene expression in ventricular cardiomyocytes that could contribute to maladaptive remodeling in accepted, long-term heart grafts.

Critical roles of cold shock domain protein A as an endogenous angiogenesis inhibitor in skeletal muscle

Angiogenesis is regulated by the local balance between angiogenic stimulators and inhibitors and is maintained by muscle-derived angiogenic factors in ischemic tissues.

AIMS

Our objectives were to investigate the effect of cold shock domain protein A (CSDA) as an endogenous angiogenesis inhibitor and to develop a novel strategy of therapeutic angiogenesis by blocking CSDA expression.

RESULTS

In human skeletal muscle cells, CSDA was upregulated during hypoxia when cells were damaged and apoptosis was induced. CSDA expression could repress the activity of hypoxia inducible factor-1α and nuclear factor κB, because CSDA can competitively bind the hypoxia response element and the nuclear factor κB-binding element. As a result, vascular endothelial growth factor-A, interleukin-6, and interleukin-8 secretions from skeletal muscle cells were decreased. Further, CSDA depletion increased the secretion level of these angiogenic factors. In a hindlimb ischemia model, transfer of short-hairpin RNA targeting CSDA ameliorated ischemia without direct transfer of angiogenic factors. In this ischemic tissue, vascular endothelial growth factor-A, interleukin-6, and CXCL2 protein levels were increased.

INNOVATION AND CONCLUSION

CSDA appears to play a critical role as an endogenous angiogenesis inhibitor in skeletal muscle, and RNA interference targeting of CSDA is a promising gene therapy strategy for treating peripheral arterial disease.

Role of the cold shock domain protein A in the transcriptional regulation of HBG expression

Impaired switching from fetal haemoglobin (HbF) to adult globin gene expression leads to hereditary persistence of fetal haemoglobin (HPFH) in adult life. This is of prime interest because elevated HbF levels ameliorate β-thalassaemia and sickle cell anaemia. Fetal haemoglobin levels are regulated by complex mechanisms involving factors linked or not to the β-globin gene (HBB) locus. To search for factors putatively involved in the expression of the γ-globin genes (HBG1, HBG2), we examined the reticulocyte transcriptome of three siblings who had different HbF levels and different degrees of β-thalassaemia severity although they had the same ΗBA- and ΗΒB cluster genotypes. By mRNA differential display we isolated the cDNA coding for the cold shock domain protein A (CSDA), also known as dbpA, previously reported to interact in vitro with the HBG2 promoter. Expression studies performed in K562 and in primary erythroid cells showed an inverse relationship between HBG and CSDA expression levels. Functional studies performed by Chromatin Immunoprecipitation and reporter gene assays in K562 cells demonstrated that CSDA is able to bind the HBG2 promoter and suppress its expression. Therefore, our study demonstrated that CSDA is a trans-acting repressor factor of HBG expression and modulates the HPFH phenotype.

Upregulation of human DNA binding protein A (dbpA) in gastric cancer cells

AIM

To determine the effect of human DNA binding protein (dbpA) on the biology of gastric cancer cells.

METHODS

DbpA expression was analyzed by Western blot analysis and immunofluorescence staining in gastric cancer tissues and cell lines. A dbpA-specific small interference (si) RNA was designed and synthesized. Suppressive effect of siRNA on dbpA expression was assessed by real-time RT-PCR. Transwell migration and colony formation assays were used to assess the inhibitory effects of dbpA siRNA on cell invasion and tumorigenesis in vitro. Drug-sensitivity was evaluated using a conventional 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide (MTT) assay.

RESULTS

The expression of dbpA was upregulated in gastric cancer tissues and cell lines as compared to adjacent normal tissues or gastric epithelial cells. siRNA treatment successfully silenced dbpA expression. Silencing of dbpA increased expression of E-cadherin, decreased expression of adenomatous polyposis coli (APC), beta-catenin and cyclin D1, but had no effect on expression of NF-kappaB. Silencing of dbpA also suppressed cell invasion and colony formation of SGC7901 cells, and enhanced their chemosensitivity to 5-fluorouracil.

CONCLUSION

DbpA plays an important role in the pathogenesis and development of gastric cancer, and the process involves E-cadherin, APC, beta-catenin and cyclin D1. Silencing of dbpA might be a novel therapeutic strategy for increasing chemosensitivity to 5-fluorouracil in gastric cancer.

Nuclease sensitive element binding protein 1 gene disruption results in early embryonic lethality

Nuclease sensitive element binding protein 1 (NSEP1) is a member of the EFIA/NSEP1/YB-1 family of DNA-binding proteins whose members share a cold shock domain; it has also been termed DNA-binding protein B and Y box binding protein-1 because of its recognition of transcriptional regulatory elements. In addition, NSEP1 functions in the translational regulation of renin, ferritin, and interleukin 2 transcripts, and our laboratory has reported that it plays a role in the biosynthesis of selenium-containing proteins. To test the functional importance of NSEP1 in murine embryonic development, we have utilized a clone of ES cells in which the NSEP1 gene had been disrupted by integration of a plasmid gene-trapping vector into the seventh exon. Injection of these cells into C57BL/6 blastocysts resulted in 11 high percentage chimeric mice; crosses to wild type C57BL/6 mice generated 82 F1 agouti mice, indicating germ line transmission of the ES cell clone, but genotyping showed no evidence of the disrupted allele in any of these agouti offspring even though spermatozoa from four of five tested mice contained the targeted allele. Embryos harvested after timed matings of chimeric male mice demonstrated only the wildtype allele in 27 embryos tested at E7.5, E12.5, and E18.5. These results suggest that gene targeting of NSEP1 induces a lethal phenotype in early embryos, due to either haploinsufficiency of NSEP1 or formation of a dominant negative form of the protein. In either case, these data indicate the functional importance of the NSEP1 gene in murine early embryonic development.

Altered expression of pro-inflammatory and developmental genes in the fetal brain in a mouse model of maternal infection

Human studies of unexplained cerebral palsy (CP) suggest an association with maternal infection. We used an established model of maternal infection, lipopolysaccharide (LPS) administration, to investigate the molecular changes in the fetal brain that may link maternal infection and CP. We compared gene expression in brains from mouse pups exposed to LPS in utero to those from saline-treated controls. Dams were injected with 50 microg LPS or saline on E18 with surgical delivery from 0.5 to 6h later. Differential gene expression was analyzed in the whole mouse brain using RT-PCR. When compared to control mice, pups exposed to LPS showed increased expression of pro-inflammatory genes monocyte chemoattractant protein-1 (MCP-1), interleukin-6 (IL-6), and interleukin-1beta (IL-1beta), as well as VEGF, a regulator of vascular development and permeability, the anti-apoptotic protein Y-box-binding protein-1 (YB-1), and the neuronal differentiation factor necdin. LPS-exposed mice also showed downregulation of semaphorin 5b and groucho, involved in axon guidance and neurogenesis, respectively, providing evidence that LPS may disrupt normal developmental pathways. These data suggest possible mechanisms for adverse neurological outcomes following maternal infection involving elevated cytokine levels and altered expression of developmental genes in the fetal brain.

Expression of Y-box-binding protein dbpC/contrin, a potentially new cancer/testis antigen

Y-box-binding proteins are members of the human cold-shock domain protein superfamily, which includes dbpA, dbpB/YB-1, and dbpC/contrin. dbpC/contrin is a germ cell-specific Y-box-binding protein and is suggested to function as a nuclear transcription factor and RNA-binding protein in the cytoplasm. Whereas ubiquitous dbpB/YB-1 expression has been well studied in various types of human carcinomas as a prognostic or predictive marker, the dbpC/contrin expression in human tumour cells has not been reported. In this report, we provide the first evidence showing that dbpC was highly expressed in human testicular seminoma and ovarian dysgerminomas, and in carcinomas in other tissues and that its expression in normal tissues is nearly restricted to germ cells and placental trophoblasts. These results indicate that dbpC/contrin would be a potentially novel cancer/testis antigen.

Expression and cellular localization of dbpC/Contrin in germ cell tumor cell lines

The transcriptional regulation of the germ cell-specific cold-shock domain protein dbpC/Contrin was investigated, and the promoter region between -272 and -253 relative to the transcription start site was shown to be critical for the manifestation of cell-type specific transcription. In vivo footprint analysis demonstrated that the E-box located between -272 and -253 is protected in the dbpC/Contrin-positive germ cell tumor cell lines NEC8 and TERA1, but not in the dbpC/Contrin-negative bladder cancer cell line T24 or ovarian cancer cell line A2780. The promoter activity of the dbpC/Contrin gene was transactivated by co-transfection with c-Myc and the N-Myc expression plasmid. Western blotting analysis clearly showed that N-Myc is highly expressed in both NEC8 and TERA1 cells, and that c-Myc is expressed in both T24 and A2780 cells. These data demonstrate that cell-type specific dbpC/Contrin expression in germ cells is regulated by N-Myc. In addition, dbpC/Contrin is localized mainly in the cytoplasm of NEC8 and TERA1 cells, but is translocated to the nucleus when its C-terminal region is partially deleted. Our findings also suggest that dbpC/Contrin can be used as a molecular tool for the detection of germ cell tumors.

Intentional delay of human hepatocarcinogenesis due to suppression of chronic hepatitis

Human hepatocellular carcinomas (HCCs) are preceded by chronic hepatitis and cirrhosis. Despite a clear viral etiology [hepatitis B virus (HBV) and hepatitis C virus (HCV)] of human hepatocarcinogenesis, the mechanism is complex and the distinct molecular pathway or molecules to explain this phenomenon are not yet known. Hepatitis viral, 'inflammation-mediated' hepatocarcinogenesis greatly influences the incidence of somatic genetic events in hepatocytes by increasing the number of target cells, or the proliferation of once-hit hepatocytes, eventually leading to HCCs. These conditions may be designated as the 'hypercarcinogenic state'. Our goal is to lead the 'hypercarcinogenic state' to the 'normo- or hypocarcinogenic' state and to prevent HCC development (intentional delay of HCC).

Construction of gene interaction and regulatory networks in bovine skeletal muscle from expression data

We propose a data-driven reverse engineering approach to isolate the components of a gene interaction and regulatory network. We apply this method to the construction of a network for bovine skeletal muscle. Key nodes in the network include muscle-specific genes and transcription factors. muscle-specific genes are identified from data mining the USA National Cancer Institute, Cancer Genome Anatomy Project database, while transcription factors are predicted by accurate function annotation. A total of 5 microarray studies spanning 78 hybridisations and 23 different experimental conditions provided raw expression data. A recently-reported analytical method based on multivariate mixed-model equations is used to compute gene co-expression measures across 624 genes. The resulting network included 102 genes (of which 40 were muscle-specific genes and 7 were transcription factors) that clustered in 7 distinct modules with clear biological interpretation.

Transcription of dbpA, a Y box binding protein, is positively regulated by E2F1: implications in hepatocarcinogenesis

Human hepatocellular carcinoma is one of the most common cancers in the world. We previously showed that dbpA, a member of the Y box family of proteins, could accelerate the process of inflammation-induced hepatocarcinogenesis, and that dbpA is more abundantly expressed in hepatocellular carcinoma than in non-tumorous tissue. In this study, to clarify the mechanism by which expression of dbpA is enhanced in the proliferative state, we examined the transcriptional activity of the dbpA promoter region. We focused on the sequence 5'-TTTGGGGC-3' (-8 to -1 in the promoter region) resembling the E2F binding site (one base mismatch, TFSEARCH score 86.2). By overexpressing E2F1 in Huh-7 cells, transcriptional activity of dbpA was significantly increased, and this increase was abolished by mutating or deleting this sequence. Thus, expression of dbpA was positively regulated by E2F1, suggesting that one of the effects of E2F1 on cell proliferation might be mediated by dbpA at the carcinogenesis step.

Developmental changes in the fetal pig transcriptome

Growth and development of pig fetuses is dependent on the coordinated expression of multiple genes. Between 21 and 45 days of gestation, fetuses experience increasing growth rates that can result in uterine crowding and increased mortality. We used differential display reverse transcription-PCR (DDRT-PCR) to identify differentially expressed genes in pig fetuses at 21, 35, and 45 days of gestation. Pig cDNAs were identified with homologies to CD3 gamma-subunit, collagen type XIV alpha1, complement component C6, craniofacial developmental protein 1, crystallin-gammaE, DNA binding protein B, epsilon-globin, formin binding protein 2, ribosomal protein L23, small acidic protein, secreted frizzled related protein 2, titin, vitamin D binding protein, and two hypothetical protein products. Two novel expressed sequence tags (ESTs) were also identified. Expression patterns were confirmed for eight genes, and spatiotemporal expression of three genes was evaluated. We identified novel transcriptome changes in fetal pigs during a period of rapid growth. These changes involved genes with a spectrum of proposed functions, including musculoskeletal growth, immune system function, and cellular regulation. This information can ultimately be used to enhance production efficiency through improved pig growth and survival.

The pleiotropic functions of the Y-box-binding protein, YB-1

The Y-box-binding protein (YB-1) represents the most evolutionary conserved nucleic-acid-binding protein currently known. YB-1 is a member of the cold-shock domain (CSD) protein superfamily. It performs a wide variety of cellular functions, including transcriptional regulation, translational regulation, DNA repair, drug resistance and stress responses to extracellular signals. As a result, YB-1 expression is closely associated with cell proliferation. In this review, we will begin by briefly describing the characteristics of YB-1 and will then summarize the pleiotropic functions brought about via DNA-RNA transaction and protein-protein interactions. In addition, we will discuss the diverse range of potential physiological and pathological functions of YB-1.

Identification of altered gene expression in skeletal muscles from Duchenne muscular dystrophy patients

Mutations in the dystrophin gene lead to dystrophin deficiency, which is the cause of Duchenne muscular dystrophy (DMD). This important discovery more than 10 years ago opened a new field for very productive investigations. However, the exact functions of dystrophin are still not fully understood and the complex process leading to subsequent muscle fiber necrosis has not been clearly described; hence there has not yet been any marked improvement in patient treatment. To decipher the molecular mechanisms induced by a lack of dystrophin, we started identifying genes whose expression is altered in DMD skeletal muscles. The approach was based on differential screening of a human muscle cDNA array. Nine genes were found to be up- or downregulated. Our results indicate expression alterations in mitochondrial genes, titin, a muscle transcription factor and three novel genes. First characterizations of these novel genes indicated that two of them have striated muscle tissue specificity.

Cold shock domain factors activate the granulocyte-macrophage colony-stimulating factor promoter in stimulated Jurkat T cells

Cold shock domain (CSD) family members have been shown to play roles in either transcriptional activation or repression of many genes in various cell types. We have previously shown that CSD proteins dbpAv and dbpB (also known as YB-1) act to repress granulocyte-macrophage colony-stimulating factor transcription in human embryonic lung (HEL) fibroblasts via binding to single-stranded DNA regions across the promoter. Here we show that the same CSD factors are involved in granulocyte-macrophage colony-stimulating factor transcriptional activation in Jurkat T cells. Unlike the mechanisms of CSD repression in HEL fibroblasts, CSD-mediated activation in Jurkat T cells is not mediated through DNA binding but presumably through protein-protein interactions via the C terminus of the CSD protein with transcription factors such as RelA/NF-kappaB p65. We demonstrate that Jurkat T cells lack truncated CSD factor subtypes present in HEL fibroblasts, which raises the possibility that the cellular content of CSD proteins may determine their final role as activators or repressors of transcription.

Gene cloning of immunogenic antigens overexpressed in pancreatic cancer

The serological analysis of recombinant cDNA expression libraries (SEREX) by utilizing a library derived from a human pancreatic adenocarcinoma cell line and IgG antibodies from an allogeneic patient serum led to the identification of 18 genes: 13 of these were known genes, and 5 were unknown genes. In Northern and RT-PCR analyses, we found that the expression of mRNA of 14 genes was elevated in pancreatic cancer cell lines compared with the levels in normal pancreatic tissues. In addition, the expression of mRNA of hsp105 in colon cancer was greater than that in normal colon tissue. Immunohistochemical analysis using anti-hsp105 antibody revealed that an increased expression of hsp105 is a characteristic feature of pancreatic ductal and colon adenocarcinoma. Furthermore, hsp105 immunoreactivity in some cases of gastric, esophageal, and hepatocellular carcinoma was much stronger than that in normal corresponding tissues. These molecules identified may provide good diagnostic markers for cancer cells.

High affinity binding of beta 2-glycoprotein I to human endothelial cells is mediated by annexin II

Beta(2)-glycoprotein I (beta(2)GPI) is an abundant plasma phospholipid-binding protein and an autoantigen in the antiphospholipid antibody syndrome. Binding of beta(2)GPI to endothelial cells targets them for activation by anti-beta(2)GPI antibodies, which circulate and are associated with thrombosis in patients with the antiphospholipid antibody syndrome. However, the binding of beta(2)GPI to endothelial cells has not been characterized and is assumed to result from association of beta(2)GPI with membrane phospholipid. Here, we characterize the binding of beta(2)GPI to endothelial cells and identify the beta(2)GPI binding site. (125)I-beta(2)GPI bound with high affinity (K(d) approximately 18 nm) to human umbilical vein endothelial cells (HUVECs). Using affinity purification, we isolated beta(2)GPI-binding proteins of approximately 78 and approximately 36 kDa from HUVECs and EAHY.926 cells. Amino acid sequences of tryptic peptides from each of these were identical to sequences within annexin II. A role for annexin II in binding of beta(2)GPI to cells was confirmed by the observations that annexin II-transfected HEK 293 cells bound approximately 10-fold more (125)I-beta(2)GPI than control cells and that anti-annexin II antibodies inhibited the binding of (125)I-beta(2)GPI to HUVECs by approximately 90%. Finally, surface plasmon resonance studies revealed high affinity binding between annexin II and beta(2)GPI. These results demonstrate that annexin II mediates the binding of beta(2)GPI to endothelial cells.

An ordered array of cold shock domain repressor elements across tumor necrosis factor-responsive elements of the granulocyte-macrophage colony-stimulating factor promoter

The tumor necrosis factor-alpha-responsive region of the human granulocyte-macrophage colony-stimulating factor (GM-CSF) promoter (-114 to -31) encompasses binding sites for NF-kappaB, CBF, AP-1, ETS, and NFAT families of transcription factors. We show both here and previously that mutation of any one of these binding sites greatly reduces tumor necrosis factor-alpha induction of the GM-CSF promoter. Interspersed between these elements are sequences that when mutated lead to an increase in GM-CSF promoter activity. We have previously shown that two of these repressor elements bind proteins known as cold shock domain (CSD) factors and that overexpression of CSD proteins leads to repression of GM-CSF promoter activity in fibroblasts. CSD proteins are single strand DNA- and RNA-binding proteins that contact 5'-CCTG-3' sequences in the GM-CSF repressor elements. We show here that two newly identified repressor sequences in the proximal promoter can also bind CSD proteins. We have characterized the CSD-containing protein complexes that bind to the GM-CSF promoter and identified a novel protein related to mitochondrial single strand binding protein that forms part of one of these complexes. The four CSD-binding sites on the promoter occur in pairs on opposite strands of the DNA and appear to form an ordered array of binding elements. A similar ordered array of CSD sites are present in the promoters of the granulocyte colony-stimulating factor and interleukin-3 genes, implying a common mechanism for negative regulation of these myeloid growth factors.

A sequence-specific RNA binding complex expressed in murine germ cells contains MSY2 and MSY4

The protamine mRNAs are stored for up to 8 days as translationally repressed ribonucleoprotein particles during murine spermatogenesis. Translational repression of the protamine 1, Prm1, mRNA is controlled by sequences in its 3'-untranslated region (UTR). In this study we used the yeast three-hybrid system to clone Msy4, which encodes a novel member of the Y box family of nucleic acid binding proteins. MSY4 specifically binds to a site within the 5' most 37 nucleotides in the Prm1 3' UTR. Msy4 is highly expressed in the testis, and the protein is detected in the cytoplasm of germ cells in both the testis and the ovary, where repressed messages are stored. Analysis of a previously described 48/50-kDa binding activity in testis extracts by electrophoretic mobility shift assays and immunoprecipitation indicates the activity is composed of MSY4 and MSY2, another mouse Y box protein. Polysome analysis demonstrates MSY4 is associated with mRNPs, consistent with MSY4 having a role in storing repressed messages.

Specifically regulated genes in malignant melanoma tissues identified by subtractive hybridization

A polymerase chain reaction (PCR)-based subtractive hybridization technique was used to identify transformation-related genes in malignant melanoma. Melanoma biopsies were compared with tissues of benign melanocytic naevi and 549 gene fragments were screened using arrayed filters. Thirty-eight clones were confirmed to be differentially expressed representing 30 different genes (18 melanoma-specific and 12 naevus-specific genes). To further confirm differential gene expression, Northern blot analyses with six of the 30 genes as probes were performed. All six were differentially expressed in benign and malignant melanocytic lesions, specifically dbpB/YB-1, 67-kDa laminin receptor, CAGH-3, 71-kDa heat shock protein and two unknown genes. The expression levels of these genes were then analysed in 50 different tissues to determine their overall expression profile. In conclusion, the technique of PCR-based subtractive hybridization in combination with arrayed filters allows detection of differences in gene expression even in tissues from which high-quality RNA is hard to isolate. The genes identified in this study are of interest because of their potential role in the pathogenesis of malignant melanoma.

RNAs from all categories generate retrosequences that may be exapted as novel genes or regulatory elements

While the significance of middle repetitive elements had been neglected for a long time, there are again tendencies to ascribe most members of a given middle repetitive sequence family a functional role--as if the discussion of SINE (short interspersed repetitive elements) function only can occupy extreme positions. In this article, I argue that differences between the various classes of retrosequences concern mainly their copy numbers. Consequently, the function of SINEs should be viewed as pragmatic such as, for example, mRNA-derived retrosequences, without underestimating the impact of retroposition for generation of novel protein coding genes or parts thereof (exon shuffling by retroposition) and in particular of SINEs (and retroelements) in modulating genes and their expression. Rapid genomic change by accumulating retrosequences may even facilitate speciation [McDonald, J.F., 1995. Transposable elements: possible catalysts of organismic evolution. Trends Ecol. Evol. 10, 123-126.] In addition to providing mobile regulatory elements, small RNA-derived retrosequences including SINEs can, in analogy to mRNA-derived retrosequences, also give rise to novel small RNA genes. Perhaps not representative for all SINE/master gene relationships, we gained significant knowledge by studying the small neuronal non-messenger RNAs, namely BC1 RNA in rodents and BC200 RNA in primates. BC1 is the first identified master gene generating a subclass of ID repetitive elements, and BC200 is the only known Alu element (monomeric) that was exapted as a novel small RNA encoding gene.

Molecular cloning of a cold-shock domain protein, zfY1, in zebrafish embryo(1)

Cold-shock domain proteins in vertebrates contain a highly conserved domain which is related to the Escherichia coli cold-shock proteins. Here we report the cloning of a cold-shock domain protein from zebrafish embryo. Using the combination of PCR techniques with degenerate primers, 5'RACE and 3'RACE, the full length cDNA of a cold-shock domain protein in the zebrafish embryo was successfully cloned without constructing and screening a library. Determined from the deduced amino acid sequence, this protein is most similar to Xenopus, FRGY1, and this newly cloned zebrafish gene was therefore designated as zfY1.

DNA binding protein dbpA binds Cdk5 and inhibits its activity

Progress in the cell cycle is governed by the activity of cyclin dependent kinases (Cdks). Unlike other Cdks, the Cdk5 catalytic subunit is found mostly in differentiated neurons. Interestingly, the only known protein that activates Cdk5 (i.e. p35) is expressed solely in the brain. It has been suggested that, besides its requirement in neuronal differentiation, Cdk5 activity is induced during myogenesis. However, it is not clear how this activity is regulated in the pathway that leads proliferative cells to differentiation. In order to find if there exists any Cdk5-interacting protein, the yeast two-hybrid system was used to screen a HeLa cDNA library. We have determined that a C-terminal 172 amino acid domain of the DNA binding protein, dbpA, binds to Cdk5. Biochemical analyses reveal that this fragment (dbpA(Cdelta)) strongly inhibits p35-activated Cdk5 kinase. The protein also interacts with Cdk4 and inhibits the Cdk4/cyclin D1 enzyme. Surprisingly, dbpA(Cdelta) does not bind Cdk2 in the two-hybrid assay nor does it inhibit Cdk2 activated by cyclin A. It could be that dbpA's ability to inhibit Cdk5 and Cdk4 reflects an apparent cross-talk between distinct signal transduction pathways controlled by dbpA on the one hand and Cdk5 or Cdk4 on the other.

drp, a novel protein expressed at high cell density but not during growth arrest

Contact is a vital mechanism used by cells to interact with their environment. Contact with living and nonliving elements adjacent to a cell is the basis for many common biological events ranging from growth regulation to metastasis to embryonic pattern formation. We describe the cloning and characterization of a novel density-regulated protein (drp) whose expression is increased in cultured cells at high density compared with cells at low density. A drp cDNA was isolated from the human teratocarcinoma cell line PA-1. Northern analysis with a drp probe revealed transcripts of 2.8 and 3.2 kb. The drp RNA was expressed in a variety of tissues, with the highest amounts in skeletal and cardiac muscle. Using antipeptide antisera, increasing amounts of a 70-kDa protein were detected using several experimental approaches in several cells lines as cell density is increased. Conditioned medium from high-density cells was unable to induce expression of drp in cells growing at low density. Similarly, growth arrest by serum starvation or transforming growth factor-beta (TGF-beta) treatment failed to elicit drp expression. We conclude that drp is a novel protein whose expression is increased at high cell density but not growth arrest.

Identification and molecular cloning of a human selenocysteine insertion sequence-binding protein. A bifunctional role for DNA-binding protein B

Prokaryotic and eukaryotic cells incorporate the unusual amino acid selenocysteine at a UGA codon, which conventionally serves as a termination signal. Translation of eukaryotic selenoprotein mRNA requires a nucleotide selenocysteine insertion sequence in the 3'-untranslated region. We report the molecular cloning of the binding protein that recognizes the selenocysteine insertion sequence element in human cellular glutathione peroxidase gene (GPX1) transcripts and its identification as DNA-binding protein B, a member of the EFIA/dbpB/YB-1 family. The predicted amino acid sequence contains four arginine-rich RNA-binding motifs, and one segment shows strong homology to the human immunodeficiency virus Tat domain. Recombinant DNA-binding protein B binds the selenocysteine insertion sequence elements from the GPX1 and type I iodothyronine 5'-deiodinase genes in RNA electrophoretic mobility shift assays and competes with endogenous GPX1 selenocysteine insertion sequence binding activity in COS-1 cytosol extracts. Addition of antibody to DNA-binding protein B to COS-1 electromobility shift assays produces a slowly migrating "supershift" band. The molecular cloning and identification of DNA-binding protein B as the first eukaryotic selenocysteine insertion sequence-binding protein opens the way to the elucidation of the entire complex necessary for the alternative reading of the genetic code that permits translation of selenoproteins.

Genomic organization of the human Y-box protein (YB-1) gene

The human Y-box protein (YB-1) is a member of a family of DNA-binding proteins containing a highly conserved cold shock domain. The genomic organization of the human YB-1 gene was determined from five overlapping genomic clones that encompassed all exons of the gene. Sequence analysis of these clones revealed that human YB-1 spans approximately 19 kb of genomic DNA and contains eight exons. The cold shock domain is encoded by exons 1-5. Both exon-splitting and codon-splitting in the region of the gene encoding the cold shock domain are similar to those in the corresponding region of another Y-box binding protein, dbpA. Exon-intron structures and nucleotide sequences of the regions encoding the N-terminal and C-terminal domains of the two proteins differ markedly between YB-1 and dbpA. These observations suggest that YB-1 and dbpA arose by duplication of a common ancestral gene encoding all these domains.

Nuclear translocation of the Y-box binding protein by ultraviolet irradiation

The Y-box binding protein, YB-1, is a member of a DNA binding protein family with a structurally and functionally conserved cold shock domain. Using Western blotting and immunohistochemical methods, larger amounts of YB-1 were detected in the cytosol, particularly at the perinuclear region, than in the nucleus of human cancer cells. UV irradiation increased accumulation of YB-1 in the nucleus at 20 min and thereafter. This translocation of YB-1 into the nucleus by UV irradiation was blocked by the protein kinase inhibitor H-7, but not HA-1004. Both green fluorescent protein (GFP)-YB-1 and GFP-YB-1C with the C-terminus (248-317) of YB-1 were located mainly in the cytosol, but GFP-YB-1deltaC with a deletion at the C-terminus of YB-1 was located in the nucleus. YB-1 is translocated into the nucleus by UV irradiation, possibly through a protein kinase C-mediated signal transduction pathway, and the C-terminal region of YB-1 might be important for cytoplasmic retention of YB-1.

Suppression of grp78 core promoter element-mediated stress induction by the dbpA and dbpB (YB-1) cold shock domain proteins

The highly conserved grp78 core promoter element plays an important role in the induction of grp78 under diverse stress signals. Previous studies have established a functional region in the 3' half of the core (stress-inducible change region [SICR]) which exhibits stress-inducible changes in stressed nuclei. The human transcription factor YY1 is shown to bind the SICR and transactivate the core element under stress conditions. Here we report that expression library screening with the core element has identified two new core binding proteins, YB-1 and dbpA. Both proteins belong to the Y-box family of proteins characterized by an evolutionarily conserved DNA binding motif, the cold shock domain (CSD). In contrast to YY1, which binds only double-stranded SICR, the Y-box/CSD proteins much prefer the lower strand of the SICR. The Y-box proteins can repress the inducibility of the grp78 core element mediated by treatment of cells with A23187, thapsigargin, and tunicamycin. In gel shift assays, YY1 binding to the core element is inhibited by either YB-1 or dbpA. A yeast interaction trap screen using LexA-YY1 as a bait and a HeLa cell cDNA-acid patch fusion library identified YB-1 as a YY1-interacting protein. In cotransfection experiments, the Y-box proteins antagonize the YY1-mediated enhancement of transcription directed by the grp78 core in stressed cells. Thus, the CSD proteins may be part of the stress signal transduction mechanism in the mammalian system.

Structural and functional analysis of the human Y-box binding protein (YB-1) gene promoter

We have isolated three overlapping genomic clones containing the 5'portion of the human YB-1 gene. These clones span approximately 25 kb of contiguous DNA containing 10 kb of 5' flanking sequence and 15 kb of the gene. The nucleotide sequence of the first exon and of 2000 upstream base pairs (bp) was determined. The first axon is unusually large and contains a 166 bp coding sequence and a 331 bp untranslated region. CpG sequences cover the 5'-end of the YB-1 gene including its first axon and intron as well as the upstream regions. The GC content around the first exon is approximately 70% and a CpG-free region was located in the untranslated sequence. The segment preceding the major transcription initiation site does not contain a TATA box, CCAAT box and the binding sequence for known transcription factors. A transient expression assay using the chloramphenicol acetyltransferase (CAT) gene showed that the sequence from +24 to +281 was critical for CAT expression. Fluorescence in situ hybridization demonstrated the chromosomal locus of YB-1 gene on chromosome 1p34. Polymerase chain reaction analysis on other genomic phage DNAs showed that several clones were derived from pseudogenes.