Project description:Liver cancer is the third most common cause of cancer death in the world. POZ/BTB and AT-hook-containing zinc finger protein 1 (PATZ1) is a transcription factor associated with various cancers. However, the role of PATZ1 in cancer progression remains controversial. Here we report that PATZ1 regulates cell proliferation by directly regulating CDKN1B (p27) in hepatocellular carcinoma HepG2 cells. PATZ1 level was found to be ectopically expressed in hepatocellular carcinoma cells compared to normal primary human hepatocytes, thus affirming its relevance in liver cancer. Our gene expression microarray and PATZ1 ChIP-seq analysis further revealed strong enrichment in gene ontology terms related to cellular proliferation. Importantly, siRNA-mediated PATZ1 knockdown in HepG2 cells led to an increased rate of colony formation, elevated Ki-67 expression and greater S phase entry. Furthermore, the increased cancer cell proliferation was accompanied with suppressed expression of the cyclin-dependent kinase inhibitor CDKN1B. Consistently, PATZ1 binds to the genomic loci flanking the transcriptional start site of CDKN1B and positively regulates its promoter activity. Additionally, we found that PATZ1 associates with p53 and the absence of p53 abrogated the PATZ1-mediated regulation of CDKN1B expression. In conclusion, our study provides novel mechanistic insights into the role of PATZ1 in liver cancer progression, thereby providing a promising therapeutic intervention to alleviate tumor burden in liver cancer.
Project description:Liver cancer is the third most common cause of cancer death in the world. POZ/BTB and AT-hook-containing zinc finger protein 1 (PATZ1) is a transcription factor associated with various cancers. However, the role of PATZ1 in cancer progression remains controversial. Here we report that PATZ1 regulates cell proliferation by directly regulating CDKN1B (p27) in hepatocellular carcinoma HepG2 cells. PATZ1 level was found to be ectopically expressed in hepatocellular carcinoma cells compared to normal primary human hepatocytes, thus affirming its relevance in liver cancer. Our gene expression microarray and PATZ1 ChIP-seq analysis further revealed strong enrichment in gene ontology terms related to cellular proliferation. Importantly, siRNA-mediated PATZ1 knockdown in HepG2 cells led to an increased rate of colony formation, elevated Ki-67 expression and greater S phase entry. Furthermore, the increased cancer cell proliferation was accompanied with suppressed expression of the cyclin-dependent kinase inhibitor CDKN1B. Consistently, PATZ1 binds to the genomic loci flanking the transcriptional start site of CDKN1B and positively regulates its promoter activity. Additionally, we found that PATZ1 associates with p53 and the absence of p53 abrogated the PATZ1-mediated regulation of CDKN1B expression. In conclusion, our study provides novel mechanistic insights into the role of PATZ1 in liver cancer progression, thereby providing a promising therapeutic intervention to alleviate tumor burden in liver cancer.
Project description:Insults to cellular health cause p53 protein accumulation and loss of p53 function leads to tumorigenesis. Thus, p53 has to be tightly controlled. Here we report that the BTB/POZ domain transcription factor PATZ1 (MAZR), previously known for its transcriptional suppressor functions in T lymphocytes, is a crucial regulator of p53. The novel inhibitory role of PATZ1 on the p53 protein marks it as a proto-oncogene. PATZ1 deficient cells have reduced proliferative capacity which we assess by RNASeq and real time cell growth rate analysis. PATZ1 modifies the expression of p53 target genes associated with cell proliferation gene ontology terms. Moreover, PATZ1 regulates several genes involved in cellular adhesion and morphogenesis. Significantly, treatment with the DNA damage inducing drug doxorubicin results in the loss of the PATZ1 transcription factor, as p53 accumulates. We find that PATZ1 binds to p53 and inhibits p53 dependent transcription activation. We examine the mechanism of this functional inhibitory interaction and demonstrate that PATZ1 excludes p53 from DNA binding. This study documents PATZ1 as a novel player in the p53 pathway. RNA-seq was used to define differentially expressed genes in wild-type and PATZ1-/- MEFs. Each sample was represented in triplicate.
Project description:White adipose tissue (WAT) plays a central role in lipid storage and systemic energy, lipid, and glucose homeostasis. Understanding the intricacies of adipocyte formation could inform therapies for obesity and metabolic disorders. We have identified the POZ/BTB and AT Hook Containing Zinc Finger 1 (PATZ1) protein as an adipogenic transcription factor through an unbiased high-throughput cDNA screen for transcriptional modulators of adipogenesis. PATZ1 is expressed by both human and mouse adipocyte precursor cells (APCs) and adipocytes, and in cell models, PATZ1 expression promotes adipogenesis through a mechanism dependent on protein-protein interaction and DNA binding. Both adipocyte-specific and APC-specific ablation of PATZ1 in mice leads to decreased fat mass and hypertrophied adipocytes. Genome-wide PATZ1 DNA binding analyses using ChIP-Seq suggest PATZ1 facilitates adipogenesis through interactions with transcription factor machinery at the promoter regions of critical early adipogenic factors and histone modifiers. Purification of the PATZ1 complex showed that General Transcription Factor 2I (GTF2I) associates with PATZ1 in a differentiation-dependent manner. Downregulation of GTF2I levels during adipogenesis markedly augments PATZ1 adipogenic function, suggesting a repressive interaction between GTF2I and PATZ1. These findings identify PATZ1 as a regulator of both adiposity and adipocyte differentiation programs and advance our understanding of the complex transcriptional mechanisms underlying adipose tissue development and homeostasis.
Project description:White adipose tissue (WAT) plays a central role in lipid storage and systemic energy, lipid, and glucose homeostasis. Understanding the intricacies of adipocyte formation could inform therapies for obesity and metabolic disorders. We have identified the POZ/BTB and AT Hook Containing Zinc Finger 1 (PATZ1) protein as an adipogenic transcription factor through an unbiased high-throughput cDNA screen for transcriptional modulators of adipogenesis. PATZ1 is expressed by both human and mouse adipocyte precursor cells (APCs) and adipocytes, and in cell models, PATZ1 expression promotes adipogenesis through a mechanism dependent on protein-protein interaction and DNA binding. Both adipocyte-specific and APC-specific ablation of PATZ1 in mice leads to decreased fat mass and hypertrophied adipocytes. Genome-wide PATZ1 DNA binding analyses using ChIP-Seq suggest PATZ1 facilitates adipogenesis through interactions with transcription factor machinery at the promoter regions of critical early adipogenic factors and histone modifiers. Purification of the PATZ1 complex showed that General Transcription Factor 2I (GTF2I) associates with PATZ1 in a differentiation-dependent manner. Downregulation of GTF2I levels during adipogenesis markedly augments PATZ1 adipogenic function, suggesting a repressive interaction between GTF2I and PATZ1. These findings identify PATZ1 as a regulator of both adiposity and adipocyte differentiation programs and advance our understanding of the complex transcriptional mechanisms underlying adipose tissue development and homeostasis.
Project description:White adipose tissue (WAT) plays a central role in lipid storage and systemic energy, lipid, and glucose homeostasis. Understanding the intricacies of adipocyte formation could inform therapies for obesity and metabolic disorders. We have identified the POZ/BTB and AT Hook Containing Zinc Finger 1 (PATZ1) protein as an adipogenic transcription factor through an unbiased high-throughput cDNA screen for transcriptional modulators of adipogenesis. PATZ1 is expressed by both human and mouse adipocyte precursor cells (APCs) and adipocytes, and in cell models, PATZ1 expression promotes adipogenesis through a mechanism dependent on protein-protein interaction and DNA binding. Both adipocyte-specific and APC-specific ablation of PATZ1 in mice leads to decreased fat mass and hypertrophied adipocytes. Genome-wide PATZ1 DNA binding analyses using ChIP-Seq suggest PATZ1 facilitates adipogenesis through interactions with transcription factor machinery at the promoter regions of critical early adipogenic factors and histone modifiers. Purification of the PATZ1 complex showed that General Transcription Factor 2I (GTF2I) associates with PATZ1 in a differentiation-dependent manner. Downregulation of GTF2I levels during adipogenesis markedly augments PATZ1 adipogenic function, suggesting a repressive interaction between GTF2I and PATZ1. These findings identify PATZ1 as a regulator of both adiposity and adipocyte differentiation programs and advance our understanding of the complex transcriptional mechanisms underlying adipose tissue development and homeostasis.
Project description:White adipose tissue (WAT) plays a central role in lipid storage and systemic energy, lipid, and glucose homeostasis. Understanding the intricacies of adipocyte formation could inform therapies for obesity and metabolic disorders. We have identified the POZ/BTB and AT Hook Containing Zinc Finger 1 (PATZ1) protein as an adipogenic transcription factor through an unbiased high-throughput cDNA screen for transcriptional modulators of adipogenesis. PATZ1 is expressed by both human and mouse adipocyte precursor cells (APCs) and adipocytes, and in cell models, PATZ1 expression promotes adipogenesis through a mechanism dependent on protein-protein interaction and DNA binding. Both adipocyte-specific and APC-specific ablation of PATZ1 in mice leads to decreased fat mass and hypertrophied adipocytes. Genome-wide PATZ1 DNA binding analyses using ChIP-Seq suggest PATZ1 facilitates adipogenesis through interactions with transcription factor machinery at the promoter regions of critical early adipogenic factors and histone modifiers. Purification of the PATZ1 complex showed that General Transcription Factor 2I (GTF2I) associates with PATZ1 in a differentiation-dependent manner. Downregulation of GTF2I levels during adipogenesis markedly augments PATZ1 adipogenic function, suggesting a repressive interaction between GTF2I and PATZ1. These findings identify PATZ1 as a regulator of both adiposity and adipocyte differentiation programs and advance our understanding of the complex transcriptional mechanisms underlying adipose tissue development and homeostasis.