Calcium channel blockers lercanidipine and amlodipine inhibit YY1/ERK/TGF-ß mediated transcription and sensitize the gastric cancer cells to doxorubicin.

Elevated expression of YY1 is known to confer anti-apoptotic phenotype and hence is an attractive target for cancer therapeutics. In a repurpose screening, towards the identification of the inhibitors of YY1 regulated transcription in gastric cancer cells, the calcium channel blockers lercanidipine and amlodipine have been identified to inhibit YY1 more efficiently. We further probed these calcium channel blockers for their potential feature of alleviating the drug resistance in gastric cancer cells. Lercanidipine and amlodipine were found to show an enhanced effect with doxorubicin in inhibiting the growth of gastric cancer cells. While doxorubicin was identified to activate the pathways TGF-ß and ERK/MAPK, lercanidipine was found to inhibit these pathways. This being the molecular mechanism behind the identified advantage of lercanidipine and amlodipine in sensitizing gastric cancer cells to doxorubicin. In multiple cellular models from different lineages, the cells with less sensitivity to doxorubicin were found to have the inherent activation of ERK/MAPK and TGF-ß pathways. Also, we have identified that doxorubicin, in combination with any of the calcium channel blockers, could inhibit the potential of cellular proliferation and spheroid formation in gastric cancer cells. The current study shows the usefulness of lercanidipine and amlodipine for the targeted and combinatorial therapeutics of gastric cancer and specifically to improve the efficiency of doxorubicin.

Regulation of miR-186-YY1 axis by the p53 translational isoform ∆40p53: implications in cell proliferation.

We have earlier shown that p53-FL and its translational isoform ∆40p53 are differentially regulated. In this study, we have investigated the cellular effect of ∆40p53 regulation on downstream gene expression, specifically miRNAs. Interestingly, ∆40p53 showed antagonistic regulation of miR-186-5p as compared to either p53 alone or a combination of both the isoforms. We have elucidated the miR-186-5p mediated effect of ∆40p53 in cell proliferation. Upon expression of ∆40p53, we observed a significant decrease in YY1 levels, an established target of miR-186-5p, which is involved in cell proliferation. Further assays with anti-miR-186 established the interdependence of ∆40p53- miR-186-5p-YY1- cell proliferation. The results unravel a new dimension toward the understanding of ∆40p53 functions, which seems to regulate cellular fate independent of p53FL.

Role of the Transcription Factor Yin Yang 1 and Its Selectively Identified Target Survivin in High-Grade B-Cells Non-Hodgkin Lymphomas: Potential Diagnostic and Therapeutic Targets.

B-cell non-Hodgkin lymphomas (B-NHLs) are often characterized by the development of resistance to chemotherapeutic drugs and/or relapse. During drug-induced apoptosis, Yin Yang 1 (YY1) transcription factor might modulate the expression of apoptotic regulators genes. The present study was aimed to: (1) examine the potential oncogenic role of YY1 in reversing drug resistance in B-NHLs; and (2) identify YY1 transcriptional target(s) that regulate the apoptotic pathway in B-NHLs. Predictive analyses coupled with database-deposited data suggested that YY1 binds the promoter of the BIRC5/survivin anti-apoptotic gene. Gene Expression Omnibus (GEO) analyses of several B-NHL repositories revealed a conserved positive correlation between YY1 and survivin, both highly expressed, especially in aggressive B-NHLs. Further validation experiments performed in Raji Burkitt's lymphomas cells, demonstrated that YY1 silencing was associated with survivin downregulation and sensitized the cells to apoptosis. Overall, our results revealed that: (1) YY1 and survivin are positively correlated and overexpressed in B-NHLs, especially in BLs; (2) YY1 strongly binds to the survivin promoter, hence survivin may be suggested as YY1 transcriptional target; (3) YY1 silencing sensitizes Raji cells to drug-induced apoptosis via downregulation of survivin; (4) both YY1 and survivin are potential diagnostic markers and therapeutic targets for the treatment of resistant/relapsed B-NHLs.

YY1-Activated Long Noncoding RNA SNHG5 Promotes Glioblastoma Cell Proliferation Through p38/MAPK Signaling Pathway.

Background: Glioma is considered one of the most prevalent and lethal brain tumors. Glioblastoma (GBM) is a main subtype of glioma. Long non-coding RNAs (lncRNAs) are identified as a new class of biomarkers and therapeutic targets for treatment of GBM. Objective: In the present study, we focused on exploring the function and potential mechanistic regulation of lncRNA small nucleolar RNA host gene 5 (SNHG5) in GBM. Methods: Gene expression was determined by qRT-PCR or western blot, as appropriate. CCK-8 and EdU assays, flow cytometry analysis and caspase 3 activity assay were conducted to evaluate several cellular processes in GBM cells. The relationship between YY1 and SNHG5 was assessed via ChIP and luciferase reporter assays. Results: SNHG5 was highly expressed in GBM. Loss- and gain-of-function assays revealed that SNHG5 promoted GBM cell proliferation and inhibited cell apoptosis in GBM. Mechanism experiments proved Yin Yang 1 (YY1) as transcriptional activator of SNHG5 in GBM. More importantly, we found that SNHG5 played the oncogenic role in GBM by activating p38/MAPK signaling pathway. Conclusion: YY1-induced SNHG5 promoted the cell proliferation in GBM via p38/MAPK signaling pathway. The findings expanded our understanding of SNHG5 as an oncogene in GBM.

Yin-Yang 1 transcription factor modulates ST2 expression during adverse cardiac remodeling post-myocardial infarction.

BACKGROUND: The cardioprotective effects of metformin remain poorly defined. Interleukin (IL)-33/ST2L signaling is a novel cardioprotective pathway, which is antagonized by the soluble isoform sST2. No data exist about the regulation of ST2 expression. This study aimed to evaluate the pathophysiological implication of Yin-Yang 1 (Yy1) transcription factor in cardiac remodeling and the expression of the soluble ST2 isoform. METHODS AND RESULTS: Myocardial infarction (MI) was induced in Wistar rats randomly receiving metformin or saline solution by permanent ligation of the left anterior coronary artery. In addition, a model of cardiomyocyte "biochemical strain" was used. Metformin administration improved post-MI cardiac remodeling, an effect that was associated with increased IL-33 and reduced sST2 levels in the myocardium. The anti-remodeling effects of metformin were also associated with a decrease in the transcription factor Yy1 intranuclear level and lower levels of phosphorylated HDAC4 within the cytoplasmic space. These effects were also observed in a cardiomyocyte biochemical strain model, where Yy1 silencing or HDAC4 inhibition blocked sST2 production in cardiomyocytes. Metformin blocked the HDAC4 phosphorylation induced by MI, preventing its export from the nucleus to the cytosol. The presence of dephosphorylated HDAC4 in the nucleus acted as a co-repressor of Yy1, repressing sST2 expression. CONCLUSION: The transcription factor Yy1 regulates sST2 expression, and repression of Yy1 by metformin results in lower levels of sST2 that are associated with favorable myocardial remodeling. The manipulation of YY1 or its co-repressor HDAC4 emerge as new targets to modulate ST2/IL33 signaling and prevent adverse cardiac remodeling.

Blocking of YY1 reduce neutrophil infiltration by inhibiting IL-8 production via the PI3K-Akt-mTOR signaling pathway in rheumatoid arthritis.

Our previous study revealed that Yin Yang 1(YY1) played an important part in promoting interleukin (IL)-6 production in rheumatoid arthritis (RA). However, whether YY1 has any role in regulation of IL-8 in RA remains unclear. YY1 and IL-8 expression in RA patients were analyzed by real-time polymerase chain reaction (PCR). Ingenuity pathway analysis (IPA) was used to analyze the signaling pathway involved in YY1-induced IL-8 production. The expression of YY1 and proteins involved in the pathway were detected by Western blot and enzyme-linked immunosorbent assay (ELISA). Migration of neutrophils was performed by chemotaxis assay. In this study, we found that high expression of IL-8 was positively associated with YY1 expression in RA. Blocking YY1 expression by YY1-short hairpin (sh)RNA lentivirus reduced IL-8 production. Mechanistically, we showed YY1 activated IL-8 production via the phosphatidylinositol-3-kinase/Akt/mammalian target of rapamycin (PI3K/Akt/mTOR) signaling pathway. Further, using a co-culture system consisting of peripheral blood mononuclear cells (PBMC) and neutrophils, we found that migration of neutrophils would be inhibited by YY1 RNA interference. Finally, using the collagen-induced arthritis animal model, we showed that treatment with the YY1-shRNA lentivirus led to reduction of IL-8 levels and attenuation of inflammation and neutrophil infiltration in vivo. Our results reveal a role of YY1 involved in neutrophil infiltration in RA via the PI3K/Akt/mTOR/IL-8 signaling pathway. YY1 may be a new therapeutic target for treatment of RA.

YY1 promotes IL-6 expression in LPS-stimulated BV2 microglial cells by interacting with p65 to promote transcriptional activation of IL-6.

Neuroinflammation plays a critical role in the process of neurodegenerative disorders, during which microglia, the principal resident immune cells in the central nervous system, are activated and produce proinflammatory mediators. Yin-Yang 1 (YY1), a multi-functional transcription factor, is widely expressed in cells of the immune system and participate in various cellular processes. However, whether YY1 is involved in the process of neuroinflammation is still unknown. In the present study, we found that YY1 was progressively up-regulated in BV2 microglial cells stimulated with lipopolysaccharide (LPS), which was dependent on the transactivation function of nuclear factor kappa B (NF-κB). Furthermore, YY1 knockdown notably inhibited LPS-induced the activation of NF-κB signaling and interleukin-6 (IL-6) expression in BV-2 cells, but not mitogen-activated protein kinase (MAPK) signaling. Moreover, YY1 strengthened p65 binding to IL-6 promoter by interacting with p65 but decreased H3K27ac modification on IL-6 promoter, eventually increasing IL-6 transcription. Taken together, these results for the first time uncover the regulatory mechanism of YY1 on IL-6 expression during neuroinflammation responses and provide new lights into neuroinflammation.

Pharmacological induction of hypoxia-inducible transcription factor ARNT attenuates chronic kidney failure.

Progression of chronic kidney disease associated with progressive fibrosis and impaired tubular epithelial regeneration is still an unmet biomedical challenge because, once chronic lesions have manifested, no effective therapies are available as of yet for clinical use. Prompted by various studies across multiple organs demonstrating that preconditioning regimens to induce endogenous regenerative mechanisms protect various organs from later incurring acute injuries, we here aimed to gain insights into the molecular mechanisms underlying successful protection and to explore whether such pathways could be utilized to inhibit progression of chronic organ injury. We identified a protective mechanism controlled by the transcription factor ARNT that effectively inhibits progression of chronic kidney injury by transcriptional induction of ALK3, the principal mediator of antifibrotic and proregenerative bone morphogenetic protein-signaling (BMP-signaling) responses. We further report that ARNT expression itself is controlled by the FKBP12/YY1 transcriptional repressor complex and that disruption of such FKBP12/YY1 complexes by picomolar FK506 at subimmunosuppressive doses increases ARNT expression, subsequently leading to homodimeric ARNT-induced ALK3 transcription. Direct targeting of FKBP12/YY1 with in vivo morpholino approaches or small molecule inhibitors, including GPI-1046, was equally effective for inducing ARNT expression, with subsequent activation of ALK3-dependent canonical BMP-signaling responses and attenuated chronic organ failure in models of chronic kidney disease, and also cardiac and liver injuries. In summary, we report an organ-protective mechanism that can be pharmacologically modulated by immunophilin ligands FK506 and GPI-1046 or therapeutically targeted by in vivo morpholino approaches.

Multifunctional YY1 in Liver Diseases.

The transcription factor Yin Yang 1 (YY1) is a multifunctional protein that can activate or repress gene expression, depending on the cellular context. While YY1 is ubiquitously expressed and highly conserved between species, its role varies among the diverse cell types and includes proliferation, differentiation, and apoptosis. Upregulated YY1 expression is found in pathogenic conditions, such as human hepatocellular carcinoma and hepatitis B virus infection, and its roles in the molecular pathogenic mechanisms in liver (i.e., fibrosis, carcinogenesis, viral-induced injury) are currently being elucidated. The most recent studies have revealed that YY1 is deeply involved in such dysregulated cellular metabolisms as glycometabolism, lipid metabolism, and bile acid metabolism, which are all involved in various diseases. In this review, we will summarize the current knowledge on YY1 in liver diseases, providing a focused discussion on the characterized and probable underlying mechanisms, as well as a reasoned evaluation of the potential for YY1-mediated pathology as drug targets in liver disease therapies.

Yin Yang 1 Dynamically Regulates Antiviral Innate Immune Responses During Viral Infection.

BACKGROUND/AIMS: Type I interferon (IFN-1) production and IFN-1 signaling play critical roles in the host antiviral innate immune responses. Although transcription factor Yin Yang 1 (YY1) has been reported to have a dual activator/repressor role during the regulation of interferon beta (IFN-ß) promoter activity, the roles of YY1 in the regulation of upstream signaling pathways leading to IFN-1 induction and IFN-1 signaling during viral infection remain to be elucidated. METHODS: The roles of YY1 in IFN-1 production and IFN-1 signaling were investigated using immunoblotting, real-time PCR, small interfering RNA (siRNA)-mediated YY1 knockdown, YY1 overexpression by transient transfection, and co-immunoprecipitation, using mouse cells. RESULTS: YY1 was shown to interact with STAT1 in the absence of viral infection. Following viral infection, YY1 protein expression levels were decreased. YY1 knockdown led to a considerable downregulation of phosphorylated (p) TBK1 and pIRF3 expressions, while YY1 overexpression significantly upregulated pTBK1 and pIRF3 expression levels and promoted virus-induced IFN-ß production. Additionally, YY1 knockdown led to a significant upregulation of pSTAT1, pSTAT2 and antiviral interferon-stimulated genes, and inhibited viral replication. CONCLUSION: We demonstrated here that YY1 interacts with STAT1 and dynamically regulates the induction of IFN-1 production and activation of IFN-1 signaling in different stages during viral infection.

Therapeutic YY1 Inhibitors in Cancer: ALL in ONE.

Various targeted therapies for cancer have resulted in a significant prolongation of survival and a better quality of life. However, unfortunately, a small subset of cancer patients responds to such therapies initially and then develops resistance after the initial therapies. Based on resistant mechanisms, it should be possible to develop new and specific targeted therapies effective against unresponsive patients. Our investigations and those of others have identified a gene product, Yin Yang 1 (YY1), a transcription factor that is overexpressed in many cancers and that was shown to be involved in the regulation of cell survival, cell proliferation, cell invasion, metastasis, and resistance. Several studies showed that the inhibition of YY1 resulted in significant inhibition of the tumor phenotype and reversal of resistance. Examples of such YY1 inhibitors include siRNA YY1, nitric oxide donors, proteasome inhibitors, and inhibitors of activated survival pathways such as inhibitors of nuclear factor-kappa beta. However, there is still a need to develop specific and targeted inhibitors of YY1. In this review, a general discussion is provided on the role of YY1 overexpression in cancer and the application of various inhibitors of YY1 activities and their potential as therapeutics.

The Forgotten YY2 in Reported YY1 Expression Levels in Human Cancers.

The transcription factor Yin Yang 1 (YY1) has been reported to be overexpressed in the majority of human cancers and that overexpression has prognostic significance. YY1 regulates several properties associated with cancer cells, including cell survival, cell proliferation, endothelial-mesenchymal transition, metastases, and resistance to both chemotherapeutics and immunotherapeutics. Although the majority of published reports focus on YY1 levels, little has been reported on the expression and activity of YY1 family member Yin Yang 2 (YY2). YY1 and YY2 share more than 50% homologies in DNA and amino acid sequences and share the same C-terminal zinc finger domains involved in DNA binding. This survey of the reported literature revealed that the antibodies used in published immunohistochemistry analyses were not uniquely specific for YY1. Most were likely cross-reactive with YY2. Furthermore, data from the Human Protein Atlas regarding YY1 and YY2 expression in various cancers were generated using antibodies that did not discriminate between YY1 and YY2. This review analyzed the commercially available antibodies listed against YY1 and YY2 and determined their cross-reactivities. A summary is of the published studies on the expression levels of YY1 in human cancers and their potential cross-reactivities with YY2 is also provided. Well-documented monospecific antibodies to both YY1 and YY2 have to be developed and used when examining the expression levels of YY1 and YY2 in human cancers to elucidate the accurate relationship between them and clinical significance of each.

Targeting the Overexpressed YY1 in Cancer Inhibits EMT and Metastasis.

There have been recent developments in the treatment of various cancers, in particular non-metastatic cancers. However, many of the responding patients often relapse initially through the development of spread micro and macro-metastases. Unfortunately, there are very few therapeutic modalities for the treatment of metastatic cancers. The development of cancer metastasis has been proposed to involve the epithelial-mesenchymal transition (EMT), in which the tumor cells with the EMT phenotype exhibit various phenotypic markers and molecular modifications that are manifested to resist most conventional therapies. YY1 is a target of the hyperactivated nuclear factor-kappa beta pathway in cancer and it was reported that YY1 also regulates cell survival and cell proliferation in addition to its role in EMT and resistance. The overexpression of YY1 in the majority of cancers has been correlated with poor prognosis. It is hypothesized that targeting YY1 may result in several anti-tumor activities, including inhibition of cell survival and cell proliferation, inhibition of EMT, and reversal of resistance. This review discusses the potential therapeutic targeting of an overexpressed transcription factor, Yin Yang 1 (YY1), which has been implicated in the development of EMT and drug resistance. Several examples targeting YY1 in experimental models are presented.

MicroRNA-29a promotes smooth muscle cell differentiation from stem cells by targeting YY1.

MicroRNA-29a (miR-29a) has been extensively studied in tumor biology and fibrotic diseases, but little is known about its functional roles in vascular smooth muscle cell (VSMC) differentiation from embryonic stem cells (ESCs). Using well-established VSMC differentiation models, we have observed that miR-29a induces VSMC differentiation from mouse ESCs by negatively regulating YY1, a transcription factor that inhibits muscle cell differentiation and muscle-specific gene expression. Moreover, gene expression levels of three VSMC specific transcriptional factors were up-regulated by miR-29a over-expression, but down-regulated by miR-29a inhibition or YY1 over-expression. Taken together, our data demonstrate that miR-29a and its target gene, YY1, play a regulatory role in VSMC differentiation from ESCs in vitro and in vivo.

Crocin Upregulates CX3CR1 Expression by Suppressing NF-κB/YY1 Signaling and Inhibiting Lipopolysaccharide-Induced Microglial Activation.

Glaucoma is a group of neurodegenerative diseases characterized by the progressive loss of retinal ganglion cells (RGCs) and optic nerve fibers. Microglial activation has been shown to be deleterious to RGCs and may participate in the progression of glaucoma. Crocin, one of the major active ingredients in saffron, has been found to inhibit microglial activation. However, the mechanism remains unclear. The aim of this study was to investigate whether crocin can inhibit lipopolysaccharide (LPS)-induced microglial activation and to clarify the mechanisms involved. The influence of crocin on primary RGCs and LPS-stimulated BV2 microglial cells survival was determined by the MTT and lactate dehydrogenase assays, or by flow cytometry. BV2 cells were pretreated with various concentrations of crocin for 2 h followed by 1 µg/mL LPS stimulation. Microglial markers and pro-inflammatory mediators were assessed by real-time PCR, western blot and ELISA. Furthermore, CX3CR1 expression was detected and the underlying mechanism was examined. The concentrations of crocin ranged from 0.1 to 1 µM, and did not show any cytotoxicity in RGC and BV2 cells. After crocin pretreatment, the expression of microglial markers (CD11b and Iba-1) and pro-inflammatory mediators (iNOS, COX-2, IL-1ß, and TNF-α) induced by LPS were significantly decreased in a dose-dependent manner. Additionally, CX3CR1 expression was remarkably increased by crocin via the suppression of NF-κB/Yin Yang 1 (YY1) signaling in BV2 cells. In conclusion, crocin effectively suppresses microglial activation and upregulates CX3CR1 expression by suppressing NF-κB/YY1 signaling.

Accumulation of p53 via down-regulation of UBE2D family genes is a critical pathway for cadmium-induced renal toxicity.

Chronic cadmium (Cd) exposure can induce renal toxicity. In Cd renal toxicity, p53 is thought to be involved. Our previous studies showed that Cd down-regulated gene expression of the UBE2D (ubiquitin-conjugating enzyme E2D) family members. Here, we aimed to define the association between UBE2D family members and p53-dependent apoptosis in human proximal tubular cells (HK-2 cells) treated with Cd. Cd increased intracellular p53 protein levels and decreased UBE2D2 and UBE2D4 gene expression via inhibition of YY1 and FOXF1 transcription factor activities. Double knockdown of UBE2D2 and UBE2D4 caused an increase in p53 protein levels, and knockdown of p53 attenuated not only Cd-induced apoptosis, but also Cd-induced apoptosis-related gene expression (BAX and PUMA). Additionally, the mice exposed to Cd for 6 months resulted in increased levels of p53 and induction of apoptosis in proximal tubular cells. These findings suggest that down-regulation of UBE2D family genes followed by accumulation of p53 in proximal tubular cells is an important mechanism for Cd-induced renal toxicity.

Regulation of Transcription Factor Yin Yang 1 by SET7/9-mediated Lysine Methylation.

Yin Yang 1 (YY1) is a multifunctional transcription factor shown to be critical in a variety of biological processes. Although it is regulated by multiple types of post-translational modifications (PTMs), whether YY1 is methylated, which enzyme methylates YY1, and hence the functional significance of YY1 methylation remains completely unknown. Here we reported the first methyltransferase, SET7/9 (KMT7), capable of methylating YY1 at two highly conserved lysine (K) residues, K173 and K411, located in two distinct domains, one in the central glycine-rich region and the other in the very carboxyl-terminus. Functional studies revealed that SET7/9-mediated YY1 methylation regulated YY1 DNA-binding activity both in vitro and at specific genomic loci in cultured cells. Consistently, SET7/9-mediated YY1 methylation was shown to involve in YY1-regulated gene transcription and cell proliferation. Our findings revealed a novel regulatory strategy, methylation by lysine methyltransferase, imposed on YY1 protein, and linked YY1 methylation with its biological functions.

The role of YY1 in oncogenesis and its potential as a drug target in cancer therapies.

Yin Yang 1 (YY1) is a multifunctional protein regulating both gene transcription and protein modifications. Recent studies reveal a proliferative role of YY1 in oncogenesis. Consistently, YY1 overexpression has been observed in various human malignancies and its levels correlate with poor prognoses of many types of cancers. In this review, we focus on the signaling pathways and regulatory proteins that YY1 modulates to promote tumor cell growth, proliferation, migration and metastasis. We also discuss the signals and molecules that regulate YY1 expression and function in cancer-related context. Based on the expression feature and regulatory activities in tumor cells, YY1 possesses a great potential as a biomarker for many cancers and can serve as a therapeutic target clinically to impede cancer development and progression or sensitize cancer cells to anticancer drugs.

Yin Yang 1 is a repressor of glutamate transporter EAAT2, and it mediates manganese-induced decrease of EAAT2 expression in astrocytes.

Impairment of astrocytic glutamate transporter (GLT-1; EAAT2) function is associated with multiple neurodegenerative diseases, including Parkinson's disease (PD) and manganism, the latter being induced by chronic exposure to high levels of manganese (Mn). Mn decreases EAAT2 promoter activity and mRNA and protein levels, but the molecular mechanism of Mn-induced EAAT2 repression at the transcriptional level has yet to be elucidated. We reveal that transcription factor Yin Yang 1 (YY1) is critical in repressing EAAT2 and mediates the effects of negative regulators, such as Mn and tumor necrosis factor alpha (TNF-α), on EAAT2. YY1 overexpression in astrocytes reduced EAAT2 promoter activity, while YY1 knockdown or mutation of the YY1 consensus site of the EAAT2 promoter increased its promoter activity and attenuated the Mn-induced repression of EAAT2. Mn increased YY1 promoter activity and mRNA and protein levels via NF-κB activation. This led to increased YY1 binding to the EAAT2 promoter region. Epigenetically, histone deacetylase (HDAC) classes I and II served as corepressors of YY1, and, accordingly, HDAC inhibitors increased EAAT2 promoter activity and reversed the Mn-induced repression of EAAT2 promoter activity. Taken together, our findings suggest that YY1, with HDACs as corepressors, is a critical negative transcriptional regulator of EAAT2 and mediates Mn-induced EAAT2 repression.

Selective targeting of the repressive transcription factors YY1 and cMyc to disrupt quiescent human immunodeficiency viruses.

Quiescent HIV-1 infection of resting CD4(+) T cells is an obstacle to eradication of HIV-1 infection. These reservoirs are maintained, in part, by repressive complexes that bind to the HIV-1 long terminal repeat (LTR) and recruit histone deacetylases (HDACs). cMyc and YY1 are two transcription factors that are recruited as part of well-described, distinct complexes to the HIV-1 LTR and in turn recruit HDACs. In prior studies, depletion of single factors that recruit HDAC1 in various cell lines was sufficient to upregulate LTR activity. We used short hairpin RNAs (shRNAs) to test the effect of targeted disruption of a single transcription factor on quiescent proviruses in T cell lines. In this study, we found that depletion of YY1 significantly increases mRNA and protein expression from the HIV-1 promoter in some contexts, but does not affect HDAC1, HDAC2, HDAC3, or acetylated histone 3 occupancy of the HIV-1 LTR. Conversely, depletion of cMyc or cMyc and YY1 does not significantly alter the level of transcription from the LTR or affect recruitment of HDACs to the HIV-1 LTR. Furthermore, global inhibition of HDACs with the HDAC inhibitor suberoylanilide hydroxamic acid (SAHA) enhanced the increase in LTR transcription in cells that were depleted of YY1.These findings show that despite prior isolated findings, redundancy in repressors of HIV-1 LTR expression will require selective targeting of multiple restrictive mechanisms to comprehensively induce the escape of quiescent proviruses from latency.