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J Biol Chem. 2001 Mar 30;276(13):10097-102. Epub 2000 Nov 21.

Dissociable Rpb4-Rpb7 subassembly of rna polymerase II binds to single-strand nucleic acid and mediates a post-recruitment step in transcription initiation.

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  • 1Banting and Best Department of Medical Research and Department of Medical Genetics and Microbiology, C. H. Best Institute, University of Toronto, Ontario M5G 1L6, Canada.

Abstract

The Rpb4 and Rpb7 subunits of yeast RNA polymerase II form a heterodimeric complex essential for promoter-directed transcription initiation in a reconstituted system. Results of template competition experiments indicate that the Rpb4-Rpb7 complex is not required for stable recruitment of polymerase to active preinitiation complexes, suggesting that Rpb4-Rpb7 mediates an essential step subsequent to promoter binding. Sequence and structure-based alignments revealed a possible OB-fold single-strand nucleic acid-binding motif in Rpb7. Purified Rpb4-Rpb7 complex exhibited both single-strand DNA- and RNA-binding activities, and a small deletion in the putative OB-fold nucleic acid-binding surface of Rpb7 abolished binding activity without affecting the stability of the Rpb4-Rpb7 complex or its ability to associate with polymerase. The same mutation destroyed the transcription activity of the Rpb4-Rpb7 complex. A separate deletion elsewhere in the OB-fold motif of Rpb7 also blocked transcription but did not affect nucleic acid binding, suggesting that the OB-fold of Rpb7 mediates both DNA-protein and protein-protein interactions required for productive initiation.

PMID:
11087726
[PubMed - indexed for MEDLINE]
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