The FACT Complex Travels with Elongating RNA Polymerase II and Is Important for the Fidelity of Transcriptional Initiation In Vivo

Abstract

The FACT complex facilitates transcription on chromatin templates in vitro, and it has been functionally linked to nucleosomes and putative RNA polymerase II (Pol II) elongation factors. In Saccharomyces cerevisiae cells, FACT specifically associates with active Pol II genes in a TFIIH-dependent manner and travels across the gene with elongating Pol II. Conditional inactivation of the FACT subunit Spt16 results in increased Pol II density, transcription, and TATA-binding protein (TBP) occupancy in the 3′ portion of certain coding regions, indicating that FACT suppresses inappropriate initiation from cryptic promoters within coding regions. Conversely, loss of Spt16 activity reduces the association of TBP, TFIIB, and Pol II with normal promoters. Thus, FACT is required for wild-type cells to restrict initiation to normal promoters, thereby ensuring that only appropriate mRNAs are synthesized. We suggest that FACT contributes to the fidelity of Pol II transcription by linking the processes of initiation and elongation.

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The FACT Complex Travels with Elongating RNA Polymerase II and Is Important for the Fidelity of Transcriptional Initiation In Vivo

ACKNOWLEDGMENTS

We thank Tim Formosa for Spt16 and Pob3 antibodies, Michael Keogh and Steve Buratowski for Tfb3 antibodies, Craig Kaplan, Fred Winston, John Lis, and Danny Reinberg for discussion of unpublished results, and Fred Winston and Rick Young for yeast strains. We thank Juliet Reid for the suggestion that polymerase redistribution in spt16 strains may be specific to distal portions of normal genes and Steve Buratowski, Michael Keogh, and Danny Reinberg for fruitful discussion.

This work was supported by an NIH postdoctoral fellowship to P.B.M. and a research grant from the National Institutes of Health to K.S. (GM 30186).