Cdc73 Subunit of Paf1 Complex Contains C-terminal Ras-like Domain That Promotes Association of Paf1 Complex with Chromatin

• Published in: The Journal of biological chemistry 2012-03, Vol.287 (14), p.10863-10875
• Main Authors: Amrich, Christopher G., Davis, Christopher P., Rogal, Walter P., Shirra, Margaret K., Heroux, Annie, Gardner, Richard G., Arndt, Karen M., VanDemark, Andrew P.
• Format: Article
• Language: English
• Subjects: 60 APPLIED LIFE SCIENCES; Amino Acid Sequence; BASIC BIOLOGICAL SCIENCES; Cdc73; CHROMATIN; Chromatin - metabolism; Conserved Sequence; CRYSTAL STRUCTURE; DEFECTS; ELONGATION; Gene Regulation; GENES; Histone Methylation; HISTONES; Histones - metabolism; LYSINE; MACHINERY; Models, Molecular; MODIFICATIONS; Molecular Sequence Data; MUTANTS; MUTATIONS; Nuclear Proteins - chemistry; Nuclear Proteins - metabolism; Paf1 Complex; Parafibromin; Protein Binding; Protein Structure, Tertiary; Protein Subunits - chemistry; Protein Subunits - metabolism; Protein Transport; PROTEINS; Ras; ras Proteins - chemistry; REGULATIONS; RESIDUES; RNA Polymerase II; RNA POLYMERASES; Saccharomyces cerevisiae - cytology; Saccharomyces cerevisiae - genetics; Saccharomyces cerevisiae - metabolism; Saccharomyces cerevisiae Proteins - chemistry; Saccharomyces cerevisiae Proteins - metabolism; Structural Biology; TATA-Box Binding Protein - metabolism; TRANSCRIPTION; Transcription Elongation; Transcription Elongation Factors; Transcription, Genetic; X-ray Crystallography
• ISSN: 0021-9258; 1083-351X
• DOI: 10.1074/jbc.M111.325647

The conserved Paf1 complex localizes to the coding regions of genes and facilitates multiple processes during transcription elongation, including the regulation of histone modifications. However, the mechanisms that govern Paf1 complex recruitment to active genes are undefined. Here we describe a previously unrecognized domain within the Cdc73 subunit of the Paf1 complex, the Cdc73 C-domain, and demonstrate its importance for Paf1 complex occupancy on transcribed chromatin. Deletion of the C-domain causes phenotypes associated with elongation defects without an apparent loss of complex integrity. Simultaneous mutation of the C-domain and another subunit of the Paf1 complex, Rtf1, causes enhanced mutant phenotypes and loss of histone H3 lysine 36 trimethylation. The crystal structure of the C-domain reveals unexpected similarity to the Ras family of small GTPases. Instead of a deep nucleotide-binding pocket, the C-domain contains a large but comparatively flat surface of highly conserved residues, devoid of ligand. Deletion of the C-domain results in reduced chromatin association for multiple Paf1 complex subunits. We conclude that the Cdc73 C-domain probably constitutes a protein interaction surface that functions with Rtf1 in coupling the Paf1 complex to the RNA polymerase II elongation machinery. Background: The Paf1 complex associates with RNA polymerase II during elongation. Results: The Cdc73 C-domain adopts a Ras-like fold that contributes to histone methylation and Paf1C recruitment to active genes. Conclusion: Cdc73 C-domain is important for Paf1 complex recruitment to genes. Significance: Rtf1 and Cdc73 C-domain combine to couple Paf1 complex to elongating polymerase.