Identification of a Yeast Transcription Factor IID Subunit, TSG2/TAF48

Joseph C Reese,Zhengjian Zhang,Harsha Kurpad

doi:10.1074/jbc.m001635200

Joseph C Reese, Zhengjian Zhang + Show 1 more

Open Access

https://doi.org/10.1074/jbc.m001635200

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Abstract

The RNA polymerase II general transcription factor TFIID is a complex containing the TATA-binding protein (TBP) and associated factors (TAFs). We have used a mutant allele of the gene encoding yeast TAF(II)68/61p to analyze its function in vivo. We provide biochemical and genetic evidence that the C-terminal alpha-helix of TAF(II)68/61p is required for its direct interaction with TBP, the stable incorporation of TBP into the TFIID complex, the integrity of the TFIID complex, and the transcription of most genes in vivo. This is the first evidence that a yeast TAF(II) other than TAF(II)145/130 interacts with TBP, and the implications of this on the interpretation of data obtained studying TAF(II) mutants in vivo are discussed. We have identified a high copy suppressor of the TAF68/61 mutation, TSG2, that has sequence similarity to a region of the SAGA subunit Ada1. We demonstrate that it directly interacts with TAF(II)68/61p in vitro, is a component of TFIID, is required for the stability of the complex in vivo, and is necessary for the transcription of many yeast genes. On the basis of these functions, we propose that Tsg2/TAF(II)48p is the histone 2A-like dimerization partner for the histone 2B-like TAF(II)68/61p in the yeast TFIID complex.

Highlights

Initiation of RNA polymerase II transcription is regulated through the concerted actions of general transcription factors, which bind near the polymerase start site, and specific transcriptional activator proteins, which bind at more distant sites [1,2,3]
On the basis of these functions, we propose that Tsg2/TAFII48p is the histone 2A-like dimerization partner for the histone 2B-like TAFII68/61p in the yeast TFIID complex
The primary amino acid sequence of a region of Tsg2/TAFII48p is highly homologous to a domain of Ada1 shown to heterodimerize with the histone fold of TAFII68/61p [29]

Summary

Introduction

Initiation of RNA polymerase II transcription is regulated through the concerted actions of general transcription factors, which bind near the polymerase start site, and specific transcriptional activator proteins, which bind at more distant sites [1,2,3]. It has been proposed that the broad transcriptional phenotypes of some TAFII mutants may result from their presence in both TFIID and the SAGA histone acetyltransferase complex [17]. Mutation or depletion of the two largest yeast TAFIIs, TSM1p or TAFII145p, has relatively minor effects on TFIID structure [9, 10]. This is surprising considering that yTAFII145p (dTAFII250) is the subunit that binds to TBP with highest affinity [6, 22,23,24], and dTAFII250 is absolutely essential to form a functional TFIID complex in biochemical reconstitution experiments [25]. There is no yeast protein that shows extensive sequence homology to hTAFII135, leaving the dimerization partner of TAFII68/61p in the yTFIID complex unidentified

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