Expression of YY1 in pro-B and T phenotypes correlation with poor survival in pediatric acute lymphoblastic leukemia.

Acute lymphoblastic leukemia (ALL) is the most common pediatric cancer, constituting 80% of all acute leukemias in minors. Despite the increase in the success of therapies, disease-free survival is over 80% in most cases. For the remaining 20% of patients, new strategies are needed to allow us to know and select those at greatest risk of relapse. We evaluated by immunohistochemistry the expression of the transcription factor YY1 and found that it is overexpressed in peripheral blood leukemia cells of pediatric patients with ALL with Pro-B and T phenotype compared to control samples. Over expression of YY1 was associated with a significantly lower chance of survival. We also evaluated by RT-PCR in bone marrow samples from ALL pediatric patients the association of YY1 expression with the percentage of blasts. High levels of YY1 were present in samples with higher percent of blasts in these patients. In addition, ALL pediatric patients with a poor response to therapy had higher levels at the nuclear level of YY1 than those who responded well to chemotherapy. In conclusion, our data suggest that YY1 could serve in pediatric ALL as markers of evolution and response for this disease, mainly in patients with pro-B and T immunophenotype. It is also suggested that YY1 is implicated in the expanse of blast in these patients.

Essential and unexpected role of Yin Yang 1 to promote mesodermal cardiac differentiation.

RATIONALE: Cardiogenesis is regulated by a complex interplay between transcription factors. However, little is known about how these interactions regulate the transition from mesodermal precursors to cardiac progenitor cells (CPCs). OBJECTIVE: To identify novel regulators of mesodermal cardiac lineage commitment. METHODS AND RESULTS: We performed a bioinformatic-based transcription factor binding site analysis on upstream promoter regions of genes that are enriched in embryonic stem cell-derived CPCs. From 32 candidate transcription factors screened, we found that Yin Yang 1 (YY1), a repressor of sarcomeric gene expression, is present in CPCs in vivo. Interestingly, we uncovered the ability of YY1 to transcriptionally activate Nkx2.5, a key marker of early cardiogenic commitment. YY1 regulates Nkx2.5 expression via a 2.1-kb cardiac-specific enhancer as demonstrated by in vitro luciferase-based assays, in vivo chromatin immunoprecipitation, and genome-wide sequencing analysis. Furthermore, the ability of YY1 to activate Nkx2.5 expression depends on its cooperative interaction with Gata4 at a nearby chromatin. Cardiac mesoderm-specific loss-of-function of YY1 resulted in early embryonic lethality. This was corroborated in vitro by embryonic stem cell-based assays in which we showed that the overexpression of YY1 enhanced the cardiogenic differentiation of embryonic stem cells into CPCs. CONCLUSIONS: These results demonstrate an essential and unexpected role for YY1 to promote cardiogenesis as a transcriptional activator of Nkx2.5 and other CPC-enriched genes.

Yin Yang 1 extends the Myc-related transcription factors network in embryonic stem cells.

The Yin Yang 1 (YY1) transcription factor is a master regulator of development, essential for early embryogenesis and adult tissues formation. YY1 is the mammalian orthologue of Pleiohomeotic, one of the transcription factors that binds Polycomb DNA response elements in Drosophila melanogaster and mediates Polycomb group proteins (PcG) recruitment to DNA. Despite several publications pointing at YY1 having a similar role in mammalians, others showed features of YY1 that are not compatible with PcG functions. Here, we show that, in mouse Embryonic Stem (ES) cells, YY1 has genome-wide PcG-independent activities while it is still stably associated with the INO80 chromatin-remodeling complex, as well as with novel RNA helicase activities. YY1 binds chromatin in close proximity of the transcription start site of highly expressed genes. Loss of YY1 functions preferentially led to a down-regulation of target genes expression, as well as to an up-regulation of several small non-coding RNAs, suggesting a role for YY1 in regulating small RNA biogenesis. Finally, we found that YY1 is a novel player of Myc-related transcription factors and that its coordinated binding at promoters potentiates gene expression, proposing YY1 as an active component of the Myc transcription network that links ES to cancer cells.

Yin Yang 1 positively regulates BRCA1 and inhibits mammary cancer formation.

Expression of the breast cancer-associated gene 1 (BRCA1) in sporadic breast cancers is usually reduced, yet the underlying mechanisms remains elusive. To identify factors that are responsible for reduced BRCA1 expression, we screened 92 known transcription factors for their ability to regulate expression of BRCA1. Among several potential regulators, the Gli-Krueppel-related transcription factor Yin Yang 1 (YY1) showed the most dramatic transactivation of the BRCA1 promoter. YY1 binds to the promoter of BRCA1, and its overexpression resulted in increased expression of BRCA1 and a number of BRCA1 downstream genes. We further showed that overexpression of YY1 in cancer cells inhibited cell proliferation, foci formation and tumor growth in nude mice. To assess the clinical relevance between YY1 and BRCA1, we studied expression of YY1 and BRCA1 from human breast cancer samples and tissue arrays, and detected a significant positive correlation between the level of YY1 and BRCA1 expression in these cancers. Taken together, these findings suggest that YY1 is a key regulator of BRCA1 expression and may be causally linked to the molecular etiology of human breast cancer.

YY1 associates with the macrosatellite DXZ4 on the inactive X chromosome and binds with CTCF to a hypomethylated form in some male carcinomas.

DXZ4 is an X-linked macrosatellite composed of 12-100 tandemly arranged 3-kb repeat units. In females, it adopts opposite chromatin arrangements at the two alleles in response to X-chromosome inactivation. In males and on the active X chromosome, it is packaged into heterochromatin, but on the inactive X chromosome (Xi), it adopts a euchromatic conformation bound by CTCF. Here we report that the ubiquitous transcription factor YY1 associates with the euchromatic form of DXZ4 on the Xi. The binding of YY1 close to CTCF is reminiscent of that at other epigenetically regulated sequences, including sites of genomic imprinting, and at the X-inactivation centre, suggesting a common mode of action in this arrangement. As with CTCF, binding of YY1 to DXZ4 in vitro is not blocked by CpG methylation, yet in vivo both proteins are restricted to the hypomethylated form. In several male carcinoma cell lines, DXZ4 can adopt a Xi-like conformation in response to cellular transformation, characterized by CpG hypomethylation and binding of YY1 and CTCF. Analysis of a male melanoma cell line and normal skin cells from the same individual confirmed that a transition in chromatin state occurred in response to transformation.

Expresión y localización del factor de transcripción Yin Yang 1 en el músculo cuádriceps en la enfermedad pulmonar obstructiva crónica / Yin Yang 1 expression and localisation in quadriceps muscle in COPD

Introducción: El Ying Yang 1 (YY1) es un factor de transcripción represor que inhibe la expresión génicamuscular y la miogénesis. Este factor no se ha investigado previamente este factor no se ha investigado enel músculo esquelético de pacientes con enfermedad pulmonar obstructiva crónica (EPOC). Los objetivosdel presente estudio fueron investigar la expresión de YY1 y su localización en el músculo cuádricepsde pacientes con EPOC, comparado con individuos control sanos, emparejados por edad, y examinar larelación entre la expresión y localización de YY1 en las áreas transversales (AT) de las fibras muscularesdel cuádriceps en pacientes con EPOC.Pacientes y métodos: Se sometió a 15 pacientes con EPOC y a 8 individuos de control, emparejados poredad, a valoraciones de la función pulmonar y del cuádriceps y a una biopsia percutánea de este músculo.Mediante inmunofluorescencia se determinó el AT de las fibras musculares del cuádriceps las proporcionesde fibras y localización de YY1. YY1 se inmunoprecipitó a partir del músculo y sus niveles se evaluaronmediante inmunotransferencia.Resultados: Los niveles de YY1 se correlacionaron inversamente con el AT de las fibras de tipo IIx y de tipo Ien pacientes e individuos de control, aunque los niveles de YY1 no fueron significativamente diferentesentre ambos grupos. En los pacientes, pero no en los individuos control, se demostró la localizaciónnuclear de YY1.Conclusión: La expresión de YY1 se asocia a un AT más pequeña de las fibras del cuádriceps en pacientescon EPOC, en cuyo músculo también se observa una localización nuclear del factor, a diferencia de losindividuos control. La regulación de YY1 parece alterada en la EPOC y podría estar implicada en la atrofiamuscular relacionada con la enfermedad(AU)

Introduction: Yin Yang 1 (YY1) is a transcriptional repressor that inhibits muscle gene expression andmyogenesis. YY1 has not previously been investigated in the skeletal muscle of patients with COPD.The aims of this study were to investigate YY1 expression and localisation in the quadriceps muscle ofCOPD patients compared to healthy age-matched controls, and examine the relationship between YY1expression and localisation and quadriceps muscle fibre cross-sectional area (CSA) in COPD patients.Patients and methods: 15 COPD patients and 8 age-matched controls underwent lung and quadriceps function assessments and a percutaneous quadriceps biopsy. Quadriceps muscle fibre CSA and fibre proportions and YY1 localisation were determined by immunofluorescence. YY1 was immunoprecipitated from muscle and YY1 levels assessed by western blotting.

Yin Yang 1 expression and localisation in quadriceps muscle in COPD.

INTRODUCTION: Yin Yang 1 (YY1) is a transcriptional repressor that inhibits muscle gene expression and myogenesis. YY1 has not previously been investigated in the skeletal muscle of patients with COPD. The aims of this study were to investigate YY1 expression and localisation in the quadriceps muscle of COPD patients compared to healthy age-matched controls, and examine the relationship between YY1 expression and localisation and quadriceps muscle fibre cross-sectional area (CSA) in COPD patients. PATIENTS AND METHODS: 15 COPD patients and 8 age-matched controls underwent lung and quadriceps function assessments and a percutaneous quadriceps biopsy. Quadriceps muscle fibre CSA and fibre proportions and YY1 localisation were determined by immunofluorescence. YY1 was immunoprecipitated from muscle and YY1 levels assessed by western blotting. RESULTS: YY1 levels were inversely correlated with type IIx and type I fibre CSA in patients and controls, though YY1 levels were not significantly different between the groups. Nuclear localisation of YY1 was demonstrated in the patients but not in controls. CONCLUSION: YY1 expression is associated with smaller quadriceps fibre CSA in COPD and nuclear localisation of YY1 was found in muscle of patients but not controls. Regulation of YY1 appears altered in COPD and may be implicated in COPD-related muscle atrophy.

A DNA variant within the MYO7A promoter regulates YY1 transcription factor binding and gene expression serving as a potential dominant DFNA11 auditory genetic modifier.

Mutations within MYO7A can lead to recessive and dominant forms of inherited hearing loss. We previously identified a large pedigree (referred to as the HL2 family) with hearing loss that first impacts the low and mid frequencies segregating a dominant MYO7A mutation in exon 17 at DNA residue G2164C. The MYO7A(G2164C) mutation predicts a nonconservative glycine-to-arginine (G722R) amino acid substitution at a highly conserved glycine residue. The degree of low and mid frequency hearing loss varies markedly in the family, suggesting the presence of a genetic modifier that either rescues or exacerbates the primary MYO7A(G2164C) mutation. Here we describe a single nucleotide polymorphism (SNP) T/C at position -4128 in the wild-type MYO7A promoter allele that sorts with the degree of hearing loss severity in the pedigree. Electrophoretic mobility shift assay analysis indicates that the SNP differentially regulates the binding of the YY1 transcription factor with the T(-4128) allele creating an YY1 binding site. Immunocytochemistry demonstrates that Yy1 is expressed in hair cell nuclei within the cochlea. Given that Myo7a is also expressed in cochlear hair cells, Yy1 shows the appropriate localization to regulate Myo7a transcription within the inner ear. YY1 appears to be acting as a transcriptional repressor as the MYO7A promoter allele containing the T(-4128) SNP drives 41 and 46% less reporter gene expression compared with the C(-4128) SNP in the ARPE-19 and HeLa cell lines, respectively. The T(-4128) SNP may be contributing to the severe hearing loss phenotype in the HL2 pedigree by reducing expression of the wild-type MYO7A allele.

Yin yang 1 is a novel regulator of pulmonary fibrosis.

RATIONALE: The differentiation of fibroblasts into myofibroblasts is a cardinal feature of idiopathic pulmonary fibrosis (IPF). The transcription factor Yin Yang 1 (YY1) plays a role in the proliferation and differentiation of diverse cell types, but its role in fibrotic lung diseases is not known. OBJECTIVES: To elucidate the mechanism by which YY1 regulates fibroblast differentiation and lung fibrosis. METHODS: Lung fibroblasts were cultured with transforming growth factor (TGF)-ß or tumor necrosis factor-α. Nuclear factor (NF)-κB, YY1, and α-smooth muscle actin (SMA) were determined in protein, mRNA, and promoter reporter level. Lung fibroblasts and lung fibrosis were assessed in a partial YY1-deficient mouse and a YY1(f/f) conditional knockout mouse after being exposed to silica or bleomycin. MEASUREMENTS AND MAIN RESULTS: TGF-ß and tumor necrosis factor-α up-regulated YY1 expression in lung fibroblasts. TGF-ß-induced YY1 expression was dramatically decreased by an inhibitor of NF-κB, which blocked I-κB degradation. YY1 is significantly overexpressed in both human IPF and murine models of lung fibrosis, including in the aggregated pulmonary fibroblasts of fibrotic foci. Furthermore, the mechanism of fibrogenesis is that YY1 can up-regulate α-SMA expression in pulmonary fibroblasts. YY1-deficient (YY1(+/-)) mice were significantly protected from lung fibrosis, which was associated with attenuated α-SMA and collagen expression. Finally, decreasing YY1 expression through instilled adenovirus-cre in floxed-YY1(f/f) mice reduced lung fibrosis. CONCLUSIONS: YY1 is overexpressed in fibroblasts in both human IPF and murine models in a NF-κB-dependent manner, and YY1 regulates fibrogenesis at least in part by increasing α-SMA and collagen expression. Decreasing YY1 expression may provide a new therapeutic strategy for pulmonary fibrosis.

Interplay between heme oxygenase-1 and the multifunctional transcription factor yin yang 1 in the inhibition of intimal hyperplasia.

RATIONALE: induction of heme oxygenase (HO)-1 protects against experimental atherosclerotic diseases, and certain pharmacological HO-1 inducers, like probucol, inhibit the proliferation of vascular smooth muscle cells and, at the same time, promote the growth of endothelial cells in vivo and in vitro. OBJECTIVE: because such cell-specific effects are reminiscent of the action of the transcription factor Yin Yang (YY)1, we tested the hypothesis that there is a functional relationship between HO-1 and YY1. METHODS AND RESULTS: we report that probucol increases the number of YY1(+) cells in rat carotid artery following balloon injury at a time coinciding with increased HO-1 expression. The drug also induces the expression of YY1 mRNA and protein in rat aortic smooth muscle cells (RASMCs) in vitro, as do other known HO-1 inducers (tert-butylhydroquinone and hemin) and overexpression of HO-1 using a human HMOX1 cDNA plasmid. Conversely, overexpression of YY1 induces expression of HO-1 in RASMCs. Induction of YY1 expression is dependent on HO-1 enzyme activity and its reaction product CO, because pharmacological inhibition of heme oxygenase activity or CO scavenging block, whereas exposure of RASMCs to a CO-releasing molecule increases, YY1 expression. Furthermore, RNA interference knockdown of YY1 prevents probucol or adeno-HO-1 from inhibiting RASMC proliferation in vitro and neointimal formation in vivo. CONCLUSIONS: our findings show, for the first time, that HO-1 functionally interplays with the multifunctional transcription factor YY1 and that this interplay explains some of the protective activities of HO-1.

Overexpression of VEGF and TGF-beta1 mRNA in Pap smears correlates with progression of cervical intraepithelial neoplasia to cancer: implication of YY1 in cervical tumorigenesis and HPV infection.

The screening of neo-angiogenesis related gene expression has uncovered many disrupted molecular pathways which may significantly confer to malignant transformation of various cell types including cervical cells. The objective of the present study was to delineate whether changes in certain gene expression profiles during the malignant conversion of the uterine cervix can be potentially used to predict the clinical course and outcome of the cervical pathology. Total RNA was isolated from Pap smears obtained from healthy females or patients diagnosed with low-grade squamous cervical intraepithelial lesions (LG-SIL), high-grade (HG)-SIL or cervical carcinoma. VEGF, TGF-beta1 and YY1 mRNA expression levels were assessed by QRT-PCR. Confirmation of YY1 protein discrepancy among cervical tissues of different histopathology was performed by immunohistochemistry. All tested genes showed statistically significant expression variations among the indicated groups. VEGF and TGF-beta1 mRNA overexpression was found to be associated with progression from low-grade to high-grade cervical intraepithelial neoplasia (CIN), while YY1 showed constitutively elevated transcript levels in CIN and cervical cancer compared to controls. At the protein level YY1 was also overexpressed in HG-SIL and cancer tissues compared to LG-SIL. Both YY1 transcript and protein overexpression were associated with HPV18- or HPV16-infected samples. Spearman analysis revealed a co-expression pattern for VEGF and TGF-beta1 mRNAs in normal cervix and LG-SIL; however, YY1 expression correlated negatively with VEGF and TGF-beta1 transcript levels upon the onset of the cervical neoplastic transformation. Our findings provide for the first time evidence for the implication of YY1 in uterine cervix carcinogenesis and suggest that VEGF, TGF-beta1 and YY1 could be useful biomarkers of cervical malignant transformation as well as potential targets for therapeutic approaches.

La expresión de Yin-Yang-1 (YY-1) y Fas en las biopsias de niños con nefritis lúpica tipo IV se correlaciona con la condición clínica / Ying-Yang (YY-1) expression and Fas in biopsies of children with type IV lupus nephritis correlates with the clinical condition

Antecedentes: La apoptosis mediada por Fas participa en la fisiopatología de la nefritis lúpica. Debido a que YY-1 regula negativamente el Fas en líneas celulares de cáncer, es razonable considerar que este factor de transcripción pueda controlar la expresión de Fas en la nefritis lúpica. El objetivo es determinar la correlación de la expresión de YY-1 y Fas en biopsias de niños con nefritis lúpica de tipo IV y su asociación con la condición clínica de los pacientes. Material y métodos: Se estudiaron 18 biopsias de niños con nefritis lúpica de tipo IV y 5 controles. La expresión de Fas y YY-1 se determinó mediante inmunohistoquímica y se cuantificó mediante análisis densitométrico. Se obtuvo información sobre el estado clínico de los pacientes en el momento de la biopsia a partir de los expedientes, y los resultados se analizaron mediante ANOVA de una vía. Se consideró significativo un valor p < 0,005. Resultados: Los resultados del análisis densitométrico muestran una relación inversa entre la expresión de YY- 1 y Fas. Se agrupó YY-1, de acuerdo con la intensidad de su expresión, en baja, moderada y alta para poder compararla con la expresión de Fas. Las biopsias de nefritis lúpica que mostraron alta expresión de YY-1 correspondieron a pacientes con menor número de complicaciones clínicas, mejor desenlace y menor número de alteraciones en la función renal. En contraste, la expresión de YY-1 baja se correlacionó con alta expresión de Fas y peores condiciones clínicas. Conclusiones: En conclusión, el presente estudio indica que YY-1 regula la expresión de Fas en la nefritis lúpica y que se encuentra asociada con el desenlace clínico de los pacientes, si bien son necesarios más estudios para determinar si puede servir como marcador pronóstico. Hasta donde sabemos, ésta es la primera evidencia de que YY-1 participa en la fisiopatología de la nefritis lúpica (AU)

Background: It has been demonstrated that Fasmediated apoptosis participates in the physiopathology of lupus nephritis, although it is not clear whether it contributes to the development of the tissue damage. Since YY-1 down regulates Fas in cancer cell lines, it is reasonable to consider that this transcription factor may control Fas expression in lupus nephritis. The objective was to determine the correlation between YY-1 and Fas expression in renal biopsies from children with type IV lupus nephritis, and their association with the clinical condition of the patients. Material and methods: Eighteen biopsies from children with type IV lupus nephritis and 5 controls were studied. Fas and YY-1 expression were determined by immunochemistry and quantified by densytometric analysis. The clinical conditions at the moment the biopsy were obtained from the clinical records and the results were analyzed through a one-way ANOVA with p < 0.005. Results: The results of the densytometric analysis showed an inverse relationship between YY-1 and Fas expression. YY-1 was grouped according to the intensity of expression in low, moderate and high and compared with the expression of Fas. The lupus nephritis biopsies, which revealed high expression of YY-1, corresponded to patients with less number of clinical complications, better outcome and fewer alterations on renal function. In contrast, low expression of YY-1 correlated with high Fas expression and worst clinical conditions. Conclusions: The present study suggests that YY-1 regulates Fas expression in lupus nephritis and that it is associated with the clinical outcome of the patients, although further studies are necessary to determine weather it factor may serve as a prognosis factor. This is the first evidence of YY-1 participation in the physiopathology of lupus nephritis (AU)