YY1 activates Msx2 gene independent of bone morphogenetic protein signaling

Multisuture craniosynostosis: a case report of unusual presentation of chromosome 14q32 deletion

Multisuture craniosynostosis is associated with a number of syndromes and underlying gene mutations. It is rarely caused by chromosome disorders. For the management, multisuture craniosynostosis raises concerns about abnormal head shape and risks of increased intracranial pressure in affected patients. Calvarial reconstruction to reshape the skull shape and expand the intracranial volume plays an essential role in correcting particular problems. Here, we report a 2-month-old female infant presenting with low birth weight, abnormal head shape, dysmorphic facies and pinnae, hypotonia, and feeding difficulty. Three-dimensional computed tomographic scans revealed left unicoronal and sagittal synostoses. Chromosome microarray analysis revealed de novo chromosome 14q32.12-q32.31 deletion. Among the deleted genes, YY1 and BCL11B are the most likely candidate genes causing craniosynostosis. Some clinical features of the patient are similar to Temple syndrome indicating that the deleted region is paternal in origin. In summary, this is a rare case of chromosome 14q32 deletion with multisuture craniosynostosis. We also report the multidisciplinary management and clinical outcomes after early cranial vault remodelling procedures.

YY1 directly suppresses MYCT1 leading to laryngeal tumorigenesis and progress

YY1 is a key transcription factor and plays different roles in various cancers. However, role and mechanism of YY1 in laryngeal cancer are still unknown. YY1 and MYCT1 mRNA and protein levels were detected by Real-time RT-PCR and Western Blot methods, respectively. Binding of YY1 to MYCT1 promoter was predicted and confirmed by bioinformatics and chromatin immunoprecipitation assays, respectively. MYCT1 promoter activity was assessed by dual luciferase assay system. Laryngeal cancer cell proliferation, migration, and apoptosis were evaluated by cell viability, colony formation, cell scratch assay, transwell assay, and flow cytometry methods, respectively. YY1 and MYCT1 were upregulated and downregulated at transcriptional level in laryngeal cancer, respectively, which showed a negative correlation between YY1 and MYCT1 expression in laryngeal cancer. Significantly higher expression of YY1 and lower expression of MYCT1 were found in laryngeal cancer tissues of patients with lymphatic metastasis than those without metastasis.YY1 directly bound to MYCT1 promoter region and inhibited its promoter activity. YY1 silence had similar biological functions as MYCT1 overexpression in repressiveness of proliferation and migration, and promotion of apoptosis in laryngeal cancer cells. However, the effects of YY1 silence were recovered by MYCT1 knockdown. YY1 promotes proliferation and migration with suppression of apoptosis via directly inhibiting MYCT1 in laryngeal cancer cells, suggesting that YY1 is a useful target as a potential oncogene in laryngeal cancer development and progression.

Positive and negative regulation of prostate stem cell antigen expression by Yin Yang 1 in prostate epithelial cell lines

Prostate cancer is influenced by epigenetic modification of genes involved in cancer development and progression. Increased expression of Prostate Stem Cell Antigen (PSCA) is correlated with development of malignant human prostate cancer, while studies in mouse models suggest that decreased PSCA levels promote prostate cancer metastasis. These studies suggest that PSCA has context-dependent functions, and could be differentially regulated during tumor progression. In the present study, we identified the multi-functional transcription factor Yin Yang 1 (YY1) as a modulator of PSCA expression in prostate epithelial cell lines. Increased YY1 levels are observed in prostatic intraepithelial neoplasia (PIN) and advanced disease. We show that androgen-mediated up-regulation of PSCA in prostate epithelial cell lines is dependent on YY1. We identified two direct YY1 binding sites within the PSCA promoter, and showed that the upstream site inhibited, while the downstream site, proximal to the androgen-responsive element, stimulated PSCA promoter activity. Thus, changes in PSCA expression levels in prostate cancer may at least partly be affected by cellular levels of YY1. Our results also suggest multiple roles for YY1 in prostate cancer which may contribute to disease progression by modulation of genes such as PSCA.

The oncogenic role of Yin Yang 1

Yin Yang 1 (YY1) is a transcription factor with diverse and complex biological functions. YY1 either activates or represses gene transcription, depending on the stimuli received by the cells and its association with other cellular factors. Since its discovery, a biological role for YY1 in tumor development and progression has been suggested because of its regulatory activities toward multiple cancer-related proteins and signaling pathways and its overexpression in most cancers. In this review, we primarily focus on YY1 studies in cancer research, including the regulation of YY1 as a transcription factor, its activities independent of its DNA binding ability, the functions of its associated proteins, and mechanisms regulating YY1 expression and activities. We also discuss the correlation of YY1 expression with clinical outcomes of cancer patients and its target potential in cancer therapy. Although there is not a complete consensus about the role of YY1 in cancers based on its activities of regulating oncogene and tumor suppressor expression, most of the currently available evidence supports a proliferative or oncogenic role of YY1 in tumorigenesis.

Yin yang-1 regulates the characterized murine focal adhesion-associated protein promoter

The focal adhesion-associated protein (FAAP), product of the murine D10Wsu52e gene, is involved in modulating cell adhesion dynamics. The ubiquitously expressed protein belongs to the highly conserved UPF0027 family, the newly identified RNA >p ligase family. To understand the mechanisms underlying FAAP expression and regulation, we first mapped its major transcription start site at the nucleotide 79  bp upstream of the ATG codon. The murine FAAP 2.1  kb 5'-flanking region was cloned, analyzed, and aligned with the corresponding 1.7  kb region of its human homolog HSPC117. Despite the differences in activity, cell in vitro transfection and testis in vivo electroporation identified a 0.2 kb efficient promoter region lacking a functional TATA-box. Gel shift assays confirmed the specific interaction between Yin Yang-1 (YY1) and the potential element in the proximal region of the FAAP promoter. Site mutation, truncation, RNAi, and overexpression analyses suggested that YY1 is an important regulator of the FAAP promoter.

YY1-dependent transcriptional regulation of the human GDAP1 gene

Charcot-Marie-Tooth disease (CMT) is a heritable neurodegenerative condition, some types of which (notably CMT4A) are caused by mutations in the GDAP1 gene that encodes a protein of unknown molecular function implicated in regulation of mitochondrial fission. Here we present for the first time a functional analysis of the GDAP1 gene promoter which we found to be transcriptionally regulated by YY1, a broadly studied factor that seems to be involved in regulating many of the same cellular phenomena as GDAP1. We show that GDAP1 is broadly expressed in cancer cell lines of different tissue origin, contrasting with the restricted neuronal distribution reported by some authors. There is a consensus YY1 binding site in the GDAP1 core promoter which we show to be functional in both in vitro binding assays and in living cells. Overexpression of YY1 activated the GDAP1 promoter in a reporter gene system as well as increased the level of endogenous mRNA. RNAi-mediated knockdown of YY1 in HEK293 cells led to decreased GDAP1 expression. While YY1 is known to exert both positive and negative regulatory influences on nuclear-encoded mitochondrial proteins, as well as on neurodegeneration-related genes, in all cell lines we studied (including neuroblastoma) the effect of YY1 on GDAP1 expression is activatory. This leads to interesting conclusions about the possible clinical role of this interaction and suggests a broader regulatory network.

Hypermethylation of homeobox A10 by in utero diethylstilbestrol exposure: an epigenetic mechanism for altered developmental programming

Diethylstilbestrol (DES) is a nonsteroidal estrogen that induces developmental anomalies of the female reproductive tract. The homeobox gene HOXA10 controls uterine organogenesis, and its expression is altered after in utero DES exposure. We hypothesized that an epigenetic mechanism underlies DES-mediated alterations in HOXA10 expression. We analyzed the expression pattern and methylation profile of HOXA10 after DES exposure. Expression of HOXA10 is increased in human endometrial cells after DES exposure, whereas Hoxa10 expression is repressed and shifted caudally from its normal location in mice exposed in utero. Cytosine guanine dinucleotide methylation frequency in the Hoxa10 intron was higher in DES-exposed offspring compared with controls (P = 0.017). The methylation level of Hoxa10 was also higher in the caudal portion of the uterus after DES exposure at the promoter and intron (P < 0.01). These changes were accompanied by increased expression of DNA methyltransferases 1 and 3b. No changes in methylation were observed after in vitro or adult DES exposure. DES has a dual mechanism of action as an endocrine disruptor; DES functions as a classical estrogen and directly stimulates HOXA10 expression with short-term exposure, however, in utero exposure results in hypermethylation of the HOXA10 gene and long-term altered HOXA10 expression. We identify hypermethylation as a novel mechanism of DES-induced altered developmental programming.

Signaling by bone morphogenetic proteins directs formation of an ectodermal signaling center that regulates craniofacial development

We previously described a signaling center, the Frontonasal Ectodermal Zone (FEZ) that regulates growth and patterning of the frontonasal process (FNP). The FEZ is comprised of FNP ectoderm flanking a boundary between Sonic hedgehog (Shh) and Fibroblast growth factor 8 (Fgf8) expression domains. Our objective was to examine BMP signaling during formation of the FEZ. We blocked BMP signaling throughout the FNP prior to FEZ formation by infecting chick embryos at stage 10 (HH10) with a replication-competent avian retrovirus encoding the BMP antagonist Noggin. We assessed gene expression patterns in the FNP 72 h after infection (approximately HH22) and observed that Shh expression was reduced or absent. In the mesenchyme, we observed that Bmp2 transcripts were absent while the Bmp4 expression domain was expanded proximally. In addition to the molecular changes, infected embryos also exhibited facial malformations at 72 and 96 h after infection suggesting that the FEZ did not form. Our data indicate that reduced cell proliferation, but not apoptosis, in the mesenchyme contributed to the phenotype that we observed. Additionally, adding exogenous SHH into the mesenchyme of RCAS-Noggin-infected embryos did not restore Bmp2 and Bmp4 to a normal pattern of expression. These data indicate that BMP signaling mediates interactions between tissues in the FNP that regulate FEZ formation; and that the correct pattern of Bmp2 and Bmp4, but not Bmp7, expression in the FNP mesenchyme requires signaling by the BMP pathway.

Functional interactions between Dlx2 and lymphoid enhancer factor regulate Msx2

Dlx2, Lymphoid Enhancer Factor (Lef-1) and Msx2 transcription factors are required for several developmental processes. To understand the control of gene expression by these factors, chromatin immunoprecipitation (ChIP) assays identified Msx2 as a downstream target of Dlx2 and Lef-1. Dlx2 activates the Msx2 promoter in several cell lines and binds DNA as a monomer and dimer. A Lef-1 beta-catenin-dependent isoform minimally activates the Msx2 promoter and a Lef-1 beta-catenin-independent isoform is inactive, however co-expression of Dlx2 and both Lef-1 isoforms synergistically activate the Msx2 promoter. Co-immunoprecipitation and protein pull-down experiments demonstrate Lef-1 physically interacts with Dlx2. Deletion analyses of the Lef-1 protein reveal specific regions required for synergism with Dlx2. The Lef-1 beta-catenin binding domain (betaDB) is not required for its interaction with Dlx2. Msx2 can auto-regulate its promoter and repress Dlx2 activation. Msx2 repression of Dlx2 activation is dose-specific and both bind a common DNA-binding element. These transcriptional mechanisms correlate with the temporal and spatial expression of these factors and may provide a mechanism for the control of several developmental processes. We demonstrate new transcriptional activities for Dlx2, Msx2 and Lef-1 through protein interactions and identification of downstream targets.

Transcription factor sumoylation and factor YY1 serve to modulate mouse amelogenin gene expression

Amelogenin proteins are essential in the control of enamel biomineralization and the amelogenin gene therefore is spatiotemporally regulated to ensure proper amelogenin protein expression. In this study, we examined the role of sumoylation to alter CCAAT/enhancer-binding protein alpha (C/EBPalpha) activity, and performed a search using a protein/DNA array system for other proteins that act co-operatively with C/EBPalpha to alter amelogenin expression. We observed that C/EBPalpha was modified by sumoylation, and that this modification played an indirect inhibitory role on the regulation of C/EBPalpha activity which appeared to act through other transcription factors. The protein/DNA array allowed us to single out the transcription factor, YY1, which acts in the absence of direct DNA binding to repress both the basal amelogenin promoter activity and C/EBPalpha-mediated transactivation. Taken together, these pathways may account for part of the physiological modulation of the amelogenin gene expression in accordance with tooth developmental and enamel biomineralization requirements.

Enhancement of long-term memory retention and short-term synaptic plasticity in cbl-b null mice

The cbl-b gene is a member of the cbl protooncogene family. It encodes a protein with multiple domains, which can interact with other proteins in a variety of signaling pathways. The functions of cbl family genes in the brain are unknown. In this report, we used genetic, immunohistochemical, behavioral, and electrophysiological approaches to study the role of cbl-b in learning and memory. Cbl-b null mice developed normally and had no abnormalities in their locomotor performance. In spatial learning and memory studies, cbl-b null and WT mice performed similarly during training. To test memory retention, two probe trials were used. cbl-b null mice performed slightly better 1 day after training. However, in the probe trial 45 days after training, the cbl-b null group showed significantly higher memory retention than WT mice, suggesting an enhancement of long-term memory. Using electrophysiological approaches, we found there was enhanced paired-pulse facilitation in the Schaffer Collateral-CA1 glutamatergic synapses of the cbl-b null mice. On the other hand, there was no difference in long-term potentiation between the two groups of mice. In summary, we provide evidence that (i) cbl-b protein is concentrated in the synaptic regions of CA1, CA3, and the dentate gyrus of the hippocampus; (ii) cbl-b null mice have enhanced long-term memory; and (iii) cbl-b null mice show an enhancement in short-term plasticity. These results indicate that cbl-b is a negative regulator of long-term memory, and its neuronal mechanism regulates synaptic transmission in the hippocampus.

Radiological trace of mandibular primary growth center in postnatal human mandibles

The mandibular primary growth center (MdPGC) of human fetus was conspicuously defined in the soft X-ray view of fetal mandibles. As the peripheral adaptive growth of mandible advances during the postnatal period, the MdPGC image became overshadowed by condensed cortical bones in soft X-ray view. In this study, we traced a sclerotic sequela of MdPGC during the postnatal period. Panoramic radiograms of 200 adults and soft X-ray views of 30 dried adult mandibles were analyzed by statistical methods. The former clearly showed an MdPGC below the middle portion of apices of canine and first premolar, which was distinguishable from mental foramen, and the latter also showed the MdPGC at the same area as a radiating and condensed radiopaque image, measuring 0.5-1.0 cm in diameter. This MdPGC position was seldom changed in the elderly people, even in the edentulous mandibles. Additionally, in the radiological examination, the benign tumors including odontogenic cysts hardly involved the MdPGC, while the malignant tumors of both primary and metastatic cancer frequently destroyed the MdPGC.

A functional SNP in the promoter region of TCOF1 is associated with reduced gene expression and YY1 DNA-protein interaction

Treacher Collins syndrome (TCS) is an autosomal dominant craniofacial malformation caused by null mutations in the TCOF1 gene. High inter and intra familial clinical variability, ranging from mild malar hypoplasia to perinatal death due to airway collapse is observed, but, to date, no genotype-phenotype correlation has been reported. Considering haploinsufficiency as the molecular mechanism underlying the disease, we have hypothesized that mutations in the promoter region of the gene, which has never been previously characterized, in trans with a pathogenic mutation, could modulate the phenotype. Therefore, the aims of the present study were to determine the TCOF1 gene's core promoter and to identify mutations in this region that could contribute to the phenotypic variation observed in this syndrome. We have delimitated the minimal promoter to a region of less than 150 bp, with 63% of identity among 5 different species. We screened 1.2 kbp of the TCOF1 5' flanking sequence in the DNA obtained from 21 patients and 51 controls and identified four new single nucleotide polymorphisms (SNPs), one of which (-346C>T), was proved to be functional, as it decreased the promoter activity by 38%. Electrophoretic mobility shift assay (EMSA) analysis demonstrated that the -346T allele impairs DNA-binding to the YY1 transcription factor. This promoter variant represents a candidate allele to explain the clinical variability in patients bearing TCS.

Marked variation in response of consensus binding elements for the Rta protein of Epstein-Barr virus

The R transactivator (Rta) protein activates Epstein-Barr virus (EBV) lytic-cycle genes by several distinct mechanisms that include direct binding to viral promoters, synergy with BamHI Z EBV replication activator (ZEBRA), and activation of cellular signaling pathways. In the direct and synergistic mechanisms of action, Rta binds to specific DNA sequences that are present in the promoters of responsive genes. It has been difficult to demonstrate the capacity of Rta expressed in mammalian cells to bind DNA in vitro in order to study the relative affinities of Rta binding elements. We discovered that a short C-terminal region of Rta inhibits the ability of Rta to bind DNA in vitro. C-terminally truncated versions of Rta bind DNA efficiently and thus facilitate a comparison of consensus Rta binding elements (CRBEs) found in promoters of five Rta-responsive genes: BMLF1, BHLF1, BMRF1, BaRF1, and BLRF2. All CRBEs in the promoters of the five genes conform to the proposed recognition sequence GNCCN9GGNG, where N is any nucleotide and N9 represents a sequence of nine nucleotides. Nonetheless, CRBEs varied markedly in their abilities to bind Rta in electrophoretic mobility shift assays. Not all CRBEs bound or responded to Rta. Binding affinities of the CRBEs and the capacity to be activated by Rta in reporter assays were strongly correlated. The CRBEs from the BMLF1 and BHLF1 promoters conferred the greatest response. The response of the BMRF1, BaRF1, and BLRF2 CRBEs was less robust. By creation of chimeras, inversions, and point mutations, differences in binding affinities and transcriptional activation levels could be attributed to N9 sequence variation. The length of N9 was also critical for a maximal response. In Raji and BZLF1-knockout cells, the mRNAs of the five Rta-responsive lytic-cycle genes differed dramatically in kinetics of expression, abundance, and synergistic responses to ZEBRA and Rta. Affinities of Rta response elements for Rta are likely to play an important role in temporal regulation and the level of lytic-cycle EBV gene expression.

YY1 is involved in RANKL-induced transcription of the tartrate-resistant acid phosphatase gene in osteoclast differentiation

Receptor activator of nuclear factor kappa B (NF-kappaB) ligand (RANKL), a critical activator of osteoclast differentiation, plays a pivotal role in tartrate-resistant acid phosphatase (TRAP) gene expression. Previously, we showed that upstream stimulatory factors (USF) 1 and 2 are implicated in the RANKL-induced TRAP transcriptional activation via a 12-bp USF binding site in the TRAP promoter. In that study, we also demonstrated that a RANKL-induced nuclear protein binds to a 50-bp oligonucleotide (Oligo IV) corresponding to a distinct TRAP promoter region. Here we report the identification and functional characterization of the nuclear protein binding to Oligo IV. We identified a 21-bp sequence CTGTTTATGATGGCGAGGGGG in Oligo IV that specifically binds the RANKL-induced nuclear protein from RAW264.7 cells by performing a series of competition assays. Computer analysis of the 21-bp sequence revealed that the sequence contains a putative Yin Yang 1 (YY1) binding site overlapped with a putative activator protein-2 (AP-2) binding site. Competition and supershift assays indicated that the nuclear protein binding to the 21-bp sequence is YY1, not AP-2. Functionally, mutation of the YY1-binding site resulted in a reduction in the RANKL-induced TRAP transcription in RAW264.7 cells, demonstrating that YY1 positively regulates RANKL-induced TRAP transcriptional activation. In conclusion, our data demonstrated that YY1 plays a functional role in RANKL-mediated TRAP gene expression during osteoclast differentiation.

A phylogenetically conserved cis-regulatory module in the Msx2 promoter is sufficient for BMP-dependent transcription in murine and Drosophila embryos

To understand the actions of morphogens, it is crucial to determine how they elicit different transcriptional responses in different cell types. Here, we identify a BMP-responsive enhancer of Msx2, an immediate early target of bone morphogenetic protein (BMP) signaling. We show that the BMP-responsive region of Msx2 consists of a core element, required generally for BMP-dependent expression, and ancillary elements that mediate signaling in diverse developmental settings. Analysis of the core element identified two classes of functional sites: GCCG sequences related to the consensus binding site of Mad/Smad-related BMP signal transducers; and a single TTAATT sequence, matching the consensus site for Antennapedia superclass homeodomain proteins. Chromatin immunoprecipitation and mutagenesis experiments indicate that the GCCG sites are direct targets of BMP restricted Smads. Intriguingly, however, these sites are not sufficient for BMP responsiveness in mouse embryos; the TTAATT sequence is also required. DNA sequence comparisons reveal this element is highly conserved in Msx2 promoters from mammalian orders but is not detectable in other vertebrates or non-vertebrates. Despite this lack of conservation outside mammals, the Msx2 BMP-responsive element serves as an accurate readout of Dpp signaling in a distantly related bilaterian - Drosophila. Strikingly, in Drosophila embryos, as in mice, both TTAATT and GCCG sequences are required for Dpp responsiveness, showing that a common cis-regulatory apparatus can mediate the transcriptional activation of BMP-regulated genes in widely divergent bilaterians.

Expression of Pax2 in the intermediate mesoderm is regulated by YY1

The transcription factor Pax2 is essential for the development of the urogenital system. Pax2 expression can be detected by mouse embryonic day 8.5 (E8.5) in the region of intermediate mesoderm fated to become the nephric duct, pronephros, and mesonephros. Elements that direct Pax2 expression to nephrogenic precursor cells must be responding to positional information that controls nephrogenic fate. A 4.1-kb Pax2 promoter/enhancer fragment directs expression of a lacZ reporter to the nephrogenic region and the midbrain-hindbrain junction in transgenic mice. As kidney development proceeds, transgene expression is limited to the nephric duct and its derivatives, but not the metanephric mesenchyme. The early expression driven by the 4.1 promoter does not require the Pax2 protein, demonstrating that it receives positional information in the absence of a developing pro- or mesonephros. We have identified two DNAseI hypersensitive regions within this promoter, one at the start site of transcription initiation and a second approximately 2-kb upstream. Deletion of the more distal site significantly attenuates lacZ expression in the nephrogenic region but not in the midbrain-hindbrain region. DNA footprinting of this fragment revealed a highly conserved sequence between mouse and human Pax2 promoter sequences. Using fractionated nuclear extracts, we identified the transcription factor Yin Yang 1 (YY1) as the protein that binds to this conserved sequence. Deletion of the YY1 element significantly attenuated expression of a full-length 4.1 promoter. Moreover, inclusion of this YY1 binding element significantly enhanced expression of a minimal Pax2 promoter/enhancer transgene in E12 embryos. These data point to a novel role for YY1 in the establishment of high level tissue-specific expression within the intermediate mesoderm.

Msx homeobox gene family and craniofacial development

Vertebrate Msx genes are unlinked, homeobox-containing genes that bear homology to the Drosophila muscle segment homeobox gene. These genes are expressed at multiple sites of tissue-tissue interactions during vertebrate embryonic development. Inductive interactions mediated by the Msx genes are essential for normal craniofacial, limb and ectodermal organ morphogenesis, and are also essential to survival in mice, as manifested by the phenotypic abnormalities shown in knockout mice and in humans. This review summarizes studies on the expression, regulation, and functional analysis of Msx genes that bear relevance to craniofacial development in humans and mice. Key words: Msx genes, craniofacial, tooth, cleft palate, suture, development, transcription factor, signaling molecule.

YY1AP, a novel co-activator of YY1

With the aim of identifying potential cellular proteins that mediate the transcriptional regulation of YY1, a HeLa cDNA library was screened using the yeast two-hybrid system. A previously unknown protein interacting with YY1 was identified and named YY1AP. By using the 5'-rapid amplification of cDNA ends technique, the full-length cDNA of YY1AP was cloned and sequenced. The cDNA was 2253 bp in length and encoded an open reading frame of 750 amino acids. The chromosomal gene was made up of 10 exons separated by nine introns and is localized on chromosome 1 (1q21.3). Northern blot analysis revealed that YY1AP is ubiquitously expressed in various human tissues and cancer cell lines. Co-immunoprecipitation and immunostaining of cells further indicated that YY1AP co-localizes with YY1 in the nucleus. Furthermore, YY1AP was shown to be capable of enhancing the transcriptional activation of an YY1 responsive promoter. Subsequent analysis by glutathione S-transferase pull-down assay showed that YY1AP contained two YY1 binding regions. The transactivation region of YY1AP would seem to be localized within the section of amino acids 260-345. It is proposed that YY1AP is a novel co-activator of YY1.