HDAC4 Promotes Growth of Colon Cancer Cells via Repression of p21

Abstract

The class II Histone deacetylase (HDAC), HDAC4, is expressed in a tissue-specific manner, and it represses differentiation of specific cell types. We demonstrate here that HDAC4 is expressed in the proliferative zone in small intestine and colon and that its expression is down-regulated during intestinal differentiation in vivo and in vitro. Subcellular localization studies demonstrated HDAC4 expression was predominantly nuclear in proliferating HCT116 cells and relocalized to the cytoplasm after cell cycle arrest. Down-regulating HDAC4 expression by small interfering RNA (siRNA) in HCT116 cells induced growth inhibition and apoptosis in vitro, reduced xenograft tumor growth, and increased p21 transcription. Conversely, overexpression of HDAC4 repressed p21 promoter activity. p21 was likely a direct target of HDAC4, because HDAC4 down-regulation increased p21 mRNA when protein synthesis was inhibited by cycloheximide. The importance of p21 repression in HDAC4-mediated growth promotion was demonstrated by the failure of HDAC4 down-regulation to induce growth arrest in HCT116 p21-null cells. HDAC4 down-regulation failed to induce p21 when Sp1 was functionally inhibited by mithramycin or siRNA-mediated down-regulation. HDAC4 expression overlapped with that of Sp1, and a physical interaction was demonstrated by coimmunoprecipitation. Chromatin immunoprecipitation (ChIP) and sequential ChIP analyses demonstrated Sp1-dependent binding of HDAC4 to the proximal p21 promoter, likely directed through the HDAC4 -HDAC3-N-CoR/SMRT corepressor complex. Consistent with increased transcription, HDAC4 or SMRT down-regulation resulted in increased histone H3 acetylation at the proximal p21 promoter locus. These studies identify HDAC4 as a novel regulator of colon cell proliferation through repression of p21. INTRODUCTIONThe acetylation of lysine residues in histones, and/or of transcription factors, is an important posttranslational mechanism of transcriptional regulation (Peterson and Laniel, 2004). Histone deacetylases (HDACs) catalyze the deacetylation of histone and nonhistone substrates, and in general act to repress transcription as part of larger corepressor complexes (Glozak et al., 2005;Yang and Gregoire, 2005). Eighteen mammalian HDACs have been identified to date, and they are grouped into four classes based on their respective homology to yeast deacetylases (Bolden et al., 2006). The class II HDACs can be further subdivided into class IIa (HDAC4, and class , based on the presence in class IIa members of conserved motifs in the N-terminal domain, and extended C terminal tails, that are essential in regulating their function (Yang and Gregoire, 2005).HDACs have emerged as critical regulators of cell growth, differentiation, and apoptotic programs (Bolden et al., 2006). A large body of literature indicates that HDAC inhibitors induce cell cycle arrest, differentiation, and apoptosis in colon cancer cell lines in vitro (Heerdt et al., 1994;Mariadason et al., 1997;Archer et al., 1998;Litvak et al., 1998;Mariadason et al.,...

Nordihydroguaiaretic acid inhibits growth of cervical cancer SiHa cells by up-regulating p21

“…However, in SiHa cells p300 loses function for mutation (27). A review of the literature showed that HDAC3-HDAC4-N-CoR/SMRT is a complex that plays a critical role in the regulation of histone acetylation associated with the p21 promoter, as HDAC4 or SMRT down-regulation results in increased histone H3 acetylation at the proximal p21 promoter (28). Our preliminary result proved that NDGA significantly down-regulated SMRT transcription.…”

HDAC4 represses p21WAF1/Cip1 expression in human cancer cells through a Sp1-dependent, p53-independent mechanism

“…As HDAC4 alone is enzymatically inactive, it may suppress p21 WAF1/Cip1 transcription by recruiting catalytically active HDACs into transcriptional corepressor complexes such as HDAC3-NCoR/SMRT (Fischle et al, 2002). While we were preparing this paper, such a model of p21 WAF1/Cip1 repression mediated by HDAC4 through association with the catalytically active HDAC3-N-CoR/SMRT corepressor complex has been shown in colon cancer cells (Wilson et al, 2008). As HDAC3 silencing did not increase p21 WAF1/Cip1 expression in IGROV-1 cells (Figure 1b), it is also possible that the mechanism by which HDAC4 represses the p21 WAF1/Cip1 promoter varies between cell types.…”

The MEF2–HDAC axis controls proliferation of mammary epithelial cells and acini formation in vitro

“…Previous results have shown that class-IIa HDACs can control CDKN1A expression (Liu et al, 2009;Mottet et al, 2009;Saramaki et al, 2009;Wilson et al, 2008); however, the mechanisms involved are debated. MEF2-binding sites are present in the genomic regions surrounding CDKN1A.…”