Control of transcriptional elongation and cotranscriptional histone modification by the yeast BUR kinase substrate Spt5.
Elongation by RNA polymerase II (RNAPII) is a finely regulated process in which many elongation factors contribute to gene regulation. Among these factors are the polymerase-associated factor (PAF) complex, which associates with RNAPII, and several cyclin-dependent kinases, including positive transcription elongation factor b (P-TEFb) in humans and BUR kinase (Bur1-Bur2) and C-terminal domain (CTD) kinase 1 (CTDK1) in Saccharomyces cerevisiae. An important target of P-TEFb and CTDK1, but not BUR kinase, is the CTD of the Rpb1 subunit of RNAPII. Although the essential BUR kinase phosphorylates Rad6, which is required for histone H2B ubiquitination on K123, Rad6 is not essential, leaving a critical substrate(s) of BUR kinase unidentified. Here we show that BUR kinase is important for the phosphorylation in vivo of Spt5, a subunit of the essential yeast RNAPII elongation factor Spt4/Spt5, whose human orthologue is DRB sensitivity-inducing factor. BUR kinase can also phosphorylate the C-terminal region (CTR) of Spt5 in vitro. Like BUR kinase, the Spt5 CTR is important for promoting elongation by RNAPII and recruiting the PAF complex to transcribed regions. Also like BUR kinase and the PAF complex, the Spt5 CTR is important for histone H2B K123 monoubiquitination and histone H3 K4 and K36 trimethylation during transcription elongation. Our results suggest that the Spt5 CTR, which contains 15 repeats of a hexapeptide whose consensus sequence is S[T/A]WGG[A/Q], is a substrate of BUR kinase and a platform for the association of proteins that promote both transcription elongation and histone modification in transcribed regions.
Zhou
Karen
K
Department of Molecular Genetics, University of Toronto, 160 College Street, Toronto, ON, Canada M5S 3E1.
Kuo
Wei Hung William
WH
Fillingham
Jeffrey
J
Greenblatt
Jack F
JF
D000595:Amino Acid Sequence; D002868:Chromosomal Proteins, Non-Histone / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D018844:Cyclin-Dependent Kinases / Q000235:genetics / Q000378:metabolism*; D016213:Cyclins / Q000235:genetics / Q000378:metabolism*; D015966:Gene Expression Regulation, Fungal; D006657:Histones / Q000378:metabolism*; D008969:Molecular Sequence Data; D012441:Saccharomyces cerevisiae / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D029701:Saccharomyces cerevisiae Proteins / Q000235:genetics / Q000378:metabolism*; D013379:Substrate Specificity; D014158:Transcription, Genetic / Q000235:genetics*; D035602:Transcriptional Elongation Factors / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*
C414164:Bur2 protein, S cerevisiae; D002868:Chromosomal Proteins, Non-Histone; D016213:Cyclins; D006657:Histones; D029701:Saccharomyces cerevisiae Proteins; D035602:Transcriptional Elongation Factors; C069940:SPT5 transcriptional elongation factor; D018844:Cyclin-Dependent Kinases; C414163:SGV1 protein, S cerevisiae