A novel TBP-TAF complex on Pol II-transcribed snRNA genes
Murphy S., Zaborowska J., Taylor A., Roeder RG.
Initiation of transcription of most human genes transcribed by pol II requires the formation of a preinitiation complex comprising TFIIA, B, D, E, F and H and pol II. The general transcription factor, TFIID is composed of the TATA-binding protein and up to 13 TBP-associated factors. Pol II does not appear to make the transition to long-range productive elongation during transcription of snRNA genes, as happens during transcription of protein-coding genes. In addition, recognition of the snRNA gene-type specific 3’ box RNA processing element requires initiation from an snRNA gene promoter. These characteristics may, at least in part, be driven by factors recruited to the promoter. For example, differences in the complement of TAFs might result in differential recruitment of elongation and RNA processing factors. It has already been shown that the promoters of some protein-coding genes do not recruit all the TAFs found in TFIID. TAF5, has been shown to be associated with pol II-transcribed snRNA genes. However, the full complement of TAFs associated with these genes was unclear. Here we show, using a ChIP and siRNA-mediated approach, that the TBP/TAF complex on snRNA genes differs from that on protein-coding genes. Interestingly, the largest TAF, TAF1 and the core TAFs, TAF10 and TAF4 are not detected on snRNA genes. We propose that this snRNA gene-specific TAF subset plays a key role in gene-type-specific control of expression.