Differential Regulation of HIC1 Target Genes by CtBP and NuRD, via an Acetylation/SUMOylation Switch, in Quiescent versus Proliferating Cells

Abstract

The tumor suppressor gene HIC1 encodes a transcriptional repressor involved in regulatory loops modulating P53-dependent and E2F1-dependent cell survival, growth control, and stress responses. Despite its importance, few HIC1 corepressors and target genes have been characterized thus far. Using a yeast two-hybrid approach, we identify MTA1, a subunit of the NuRD complex, as a new HIC1 corepressor. This interaction is regulated by two competitive posttranslational modifications of HIC1 at lysine 314, promotion by SUMOylation, and inhibition by acetylation. Consistent with the role of HIC1 in growth control, we demonstrate that HIC1/MTA1 complexes bind on two new target genes, Cyclin D1 and p57KIP2 in quiescent but not in growing WI38 cells. In addition, HIC1/MTA1 and HIC1/CtBP complexes differentially bind on two mutually exclusive HIC1 binding sites (HiRE) on the SIRT1 promoter. SIRT1 transcriptional activation induced by short-term serum starvation coincides with loss of occupancy of the distal sites by HIC1/MTA1 and HIC1/CtBP. Upon longer starvation, both complexes are found but on a newly identified proximal HiRE that is evolutionarily conserved and specifically enriched with repressive histone marks. Our results decipher a mechanistic link between two competitive posttranslational modifications of HIC1 and corepressor recruitment to specific genes, leading to growth control.HIC1 (Hypermethylated in Cancer 1), a tumor suppressor gene frequently deleted or epigenetically silenced in human cancers, encodes a transcriptional repressor (7,20,65). A regulatory feedback loop between HIC1 and P53 has been deciphered. HIC1 is a direct target gene of P53 (5, 24, 65). HIC1 directly represses the transcription of SIRT1, a NAD ϩ -dependent class III histone deacetylase (HDAC) that deacetylates and inactivates P53, thereby modulating P53-dependent DNA damage responses (8). We have shown that SIRT1 also deacetylates HIC1. In contrast to P53, this deacetylation activates HIC1 by strengthening its transcriptional repression potential (59).Aside from P53, SIRT1 and HIC1 have also been implicated in a feedback regulatory loop with E2F1. E2F1 is a crucial activator of SIRT1 transcription in response to DNA damage, but SIRT1 binds and deacetylates E2F1 that inhibits E2F1-mediated gene activation (30, 66). In addition, E2F1 directly activates HIC1 (27) and HIC1 directly represses the E2F1 promoter in quiescent but not in G 1 human fibroblasts, which contributes to the growth suppression induced by serum deprivation (71). Thus, HIC1 is placed at the intersection of complex regulatory loops modulating p53-dependent and E2F1-dependent cell survival, growth control, and stress responses (15).HIC1 encodes a sequence-specific transcriptional repressor with five Krüppel-like C 2 H 2 zinc fingers mediating DNA binding to a HIC1 responsive element (HiRE), (C/G)NG(C/ G)GGGCA(C/A)CC (48). To date, SIRT1, ATOH1 (a proneuronal transcription factor) (4), E2F1, CXCR7 (a receptor for the chemokine CXCL12) (62), and ephrin-A1 (a cell surface liga...

The transcriptional repressor HIC1 regulates intestinal immune homeostasis

“…36,37 Further, HIC1 has also been shown to indirectly repress transcription by binding to transcriptional activators and preventing binding to target genes. HIC1 has been shown to interact with and inhibit DNA binding of transcription factors such as T-cell factor-4, b-catenin, and STAT3.…”

“…44,45 HIC1 has been shown to interact with and regulate key transcription factors involved in cell cycle progression and cellular metabolism. 37,46 For example, HIC1 is involved in a regulatory feed back loop with the deacteylase SIRT1, 17 which is a key regulator of fattyacid oxidation. 47 Further, it has been demonstrated that fattyacid metabolism is key to memory T-cell development and survival.…”

Loss of Hypermethylated in Cancer 1 (HIC1) in Breast Cancer Cells Contributes to Stress-induced Migration and Invasion through β-2 Adrenergic Receptor (ADRB2) Misregulation

“…Western blotting was performed as previously described (8). Results are representative of at least two experiments.…”

“…HIC1 is able to recruit different co-repressor complexes to its target genes, using short motifs in its central region notably CtBP through a GLDLSKK motif (7), and MTA1, a component of the NuRD complex, through a SUMOylation-dependent ⌿KXEP motif (8). HIC1 also recruits BRG1-ARID1A containing SWI/SNF complexes (9).…”

“…To date, ten target genes play supporting roles in developmental and cell cycle control: histone deacetylase SIRT1 (10), the transcription factors ATOH1 (11), Sox9 (12), and ⌬Np73 (13), the G-protein coupled receptor CXCR7 (14), Cyclin D1 and P57KIP2 (CDKN1C) (8) and EFNA1, a cell surface ligand for Eph tyrosine kinase receptors (15).…”