Involvement of the Histone Deacetylase SIRT1 in Chicken Ovalbumin Upstream Promoter Transcription Factor (COUP-TF)-interacting Protein 2-mediated Transcriptional Repression

Thanaset Senawong,Valerie J Peterson,Dorina Avram,David M Shepherd,Roy A Frye,Saverio Minucci,Mark Leid

doi:10.1074/jbc.m307477200

Abstract

Chicken ovalbumin upstream promoter transcription factor (COUP-TF)-interacting proteins 1 and 2 (CTIP1 and CTIP2) enhance transcriptional repression mediated by COUP-TF II and have been implicated in hematopoietic cell development and malignancies. CTIP1 and CTIP2 are also sequence-specific DNA-binding proteins that repress transcription through direct, COUP-TF-in-dependent binding to a GC-rich response element. CTIP1- and CTIP2-mediated transcriptional repression is insensitive to trichostatin A, an inhibitor of known class I and II histone deacetylases. However, chromatin immunoprecipitation assays revealed that expression of CTIP2 in mammalian cells resulted in deacetylation of histones H3 and/or H4 that were associated with the promoter region of a reporter gene. CTIP2-mediated transcriptional repression, as well as deacetylation of promoter-associated histones H3/H4 in CTIP2-transfected cells, was reversed by nicotinamide, an inhibitor of class III histone deacetylases such as the mammalian homologs of yeast Silent Information Regulator 2 (Sir2). The human homolog of yeast Sir2, SIRT1, was found to interact directly with CTIP2 and was recruited to the promoter template in a CTIP2-dependent manner. Moreover, SIRT1 enhanced the deacetylation of template-associated histones H3/H4 in CTIP2-transfected cells, and stimulated CTIP2-dependent transcriptional repression. Finally, endogenous SIRT1 and CTIP2 co-purified from Jurkat cell nuclear extracts in the context of a large (1-2 mDa) complex. These findings implicate SIRT1 as a histone H3/H4 deacetylase in mammalian cells and in transcriptional repression mediated by CTIP2.

Highlights

CTIP11 (EVI9 or BCL11A) and CTIP2 (BCL11B) are two related C2H2 zinc finger proteins that were originally isolated and identified as COUP-TF-interacting proteins [1]
CTIP2-mediated Transcriptional Repression Is Partially Reversed by Nicotinamide, an Inhibitor of NADϩ-dependent Deacetylases—Previous studies indicated that CTIP1-mediated transcriptional repression was independent of trichostatin A (TSA)-sensitive histone deacetylation [1, 2]
Considered together, these findings suggest that neither CTIP1- nor CTIP2-mediated transcriptional repression involves recruitment of class I or class II TSA-sensitive HDACs to the template

Summary

Introduction

CTIP11 (EVI9 or BCL11A) and CTIP2 (BCL11B) are two related C2H2 zinc finger proteins that were originally isolated and identified as COUP-TF-interacting proteins [1]. CTIP12 [1] and CTIP2 both enhance COUP-TFII-mediated transcriptional repression in transfected cells independently of trichostatin A (TSA)-sensitive histone deacetylation. It is likely that CTIPs either function with other nuclear receptors in cells of lymphoid origin or act as COUP-TF-independent transcription factors in these cells The latter appears to be true as CTIP1 and CTIP2 have been demonstrated to repress expression of a reporter gene through direct binding to a recently identified binding site, 5Ј-GGCCGGAGG-3Ј (upper strand) [2]. This repression was observed in the absence of cotransfected COUP-TF proteins and was insensitive to reversal by TSA [2]. Various in vitro inhibitors of SIRT isozymes have been described, the catalytic activity of class III HDACs is not inhibited by TSA but may be inhibited by nicotinamide, a product of the SIRT-mediated deacetylation reaction [28, 34, 35]

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Results

Conclusion