Abstract
TFIIB is the only factor within the multimegadalton transcription complex that is obligatorily required to undergo dissociation and re-association with each round of mRNA transcription. Here we show that a six-amino acid human TFIIB tip region is needed for appropriate levels of serine 5 C-terminal domain phosphorylation and mRNA capping and for retention of the required elongation factor TFIIF. We suggest that the broad functions of this tiny region are used to suppress transcription noise by restricting functional RNA synthesis from non-promoter sites on the genome, which will not contain TFIIB.
Highlights
TFIIB is known to both directly recruit RNA polymerase and to alter its enzymatic properties [2,3,4]
The B-tip Is Needed for the Retention of TFIIF during Elongation—Previously, it was shown that TFIIB tip is important during promoter escape [3]
To learn if the tip has a role in the fate of TFIIF, we assayed TFIIF association with the transcription complex using a slightly modified prior protocol [3] for assaying factor retention by TFIIB and its mutants
Summary
TFIIB is known to both directly recruit RNA polymerase and to alter its enzymatic properties [2,3,4]. These data raise the possibility that the TFIIB tip cooperates with TFIIF during promoter escape to allow formation of scaffolds and elongation complexes that produce appropriate levels of properly processed RNAs. The TFIIB tip region consists of the pair of aspartate residues separated by four amino acids.
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