Acetylation of general transcription factors by histone acetyltransferases

Abstract

The acetylation of histones increases the accessibility of nucleosomal DNA to transcription factors [1], [2], relieving transcriptional repression [3] and correlating with the potential for transcriptional activity in vivo[4], [5], [6], [7]. The characterization of several novel histone acetyltransferases –  including the human GCN5 homolog PCAF (p300/CBP-associated factor) [8], the transcription coactivator p300/CBP [9], and TAF_II250 [10] –  has provided a potential explanation for the relationship between histone acetylation and transcriptional activation. In addition to histones, however, other components of the basal transcription machinery might be acetylated by these enzymes and directly affect transcription. Here, we examine the acetylation of the basal transcriptional machinery for RNA polymerase II by PCAF, p300 and TAF_II250. We find that all three acetyltransferases can direct the acetylation of TFIIEβand TFIIF, and we identify a preferred site of acetylation in TFIIEβ. Human TFIIE consists of two subunits, α(p56) and β(p34), which form a heterotetramer (α₂β₂) in solution ([11], reviewed in [12]). TFIIE enters the preinitiation complex after RNA polymerase II and TFIIF, suggesting that TFIIE may interact directly with RNA polymerase II and/or TFIIF [13], [14]. In addition, TFIIE can facilitate promoter melting either in the presence or absence of TFIIH and can stimulate TFIIH-dependent phosphorylation of the carboxy-terminal domain of RNA polymerase II [15], [16], [17], [18]. TFIIF has an essential role in both transcription initiation and elongation ([19], [20], for review see [21]). We discuss the implications of the acetylation of TFIIEβand TFIIF for transcriptional control by PCAF, p300 and TAF_II250.