The Iws1:Spt6:CTD complex controls cotranscriptional mRNA biosynthesis and HYPB/Setd2-mediated histone H3K36 methylation.
Many steps in gene expression and mRNA biosynthesis are coupled to transcription elongation and organized through the C-terminal domain (CTD) of the large subunit of RNA polymerase II (RNAPII). We showed recently that Spt6, a transcription elongation factor and histone H3 chaperone, binds to the Ser2P CTD and recruits Iws1 and the REF1/Aly mRNA export adaptor to facilitate mRNA export. Here we show that Iws1 also recruits the HYPB/Setd2 histone methyltransferase to the RNAPII elongation complex and is required for H3K36 trimethylation (H3K36me3) across the transcribed region of the c-Myc, HIV-1, and PABPC1 genes in vivo. Interestingly, knockdown of either Iws1 or HYPB/Setd2 also enhanced H3K27me3 at the 5' end of the PABPC1 gene, and depletion of Iws1, but not HYPB/Setd2, increased histone acetylation across the coding regions at the HIV-1 and PABPC1 genes in vivo. Knockdown of HYPB/Setd2, like Iws1, induced bulk HeLa poly(A)+ mRNAs to accumulate in the nucleus. In vitro, recombinant Spt6 binds selectively to a stretch of uninterrupted consensus repeats located in the N-terminal half of the CTD and recruits Iws1. Thus Iws1 connects two distinct CTD-binding proteins, Spt6 and HYPB/Setd2, in a megacomplex that affects mRNA export as well as the histone modification state of active genes.
Yoh
Sunnie M
SM
Regulatory Biology Laboratory, The Salk Institute for Biological Studies, La Jolla, California 92037, USA.
Lucas
Joseph S
JS
Jones
Katherine A
KA
D000107:Acetylation; D000818:Animals; D002460:Cell Line; D002467:Cell Nucleus / Q000378:metabolism; D005786:Gene Expression Regulation; D055785:Gene Knockdown Techniques; D015497:HIV-1 / Q000235:genetics; D011495:Histone-Lysine N-Methyltransferase / Q000378:metabolism*; D006657:Histones / Q000378:metabolism*; D006801:Humans; D019169:Jurkat Cells; D051741:Kruppel-Like Transcription Factors / Q000235:genetics / Q000378:metabolism*; D008745:Methylation; D051379:Mice; D039122:Poly(A)-Binding Protein I / Q000235:genetics; D011485:Protein Binding; D011506:Proteins / Q000235:genetics / Q000378:metabolism*; D012319:RNA Polymerase II / Q000235:genetics / Q000378:metabolism*; D012333:RNA, Messenger / Q000096:biosynthesis* / Q000378:metabolism; D016601:RNA-Binding Proteins; D014157:Transcription Factors
D006657:Histones; C510636:Iws1 protein, human; D051741:Kruppel-Like Transcription Factors; D039122:Poly(A)-Binding Protein I; D011506:Proteins; D012333:RNA, Messenger; D016601:RNA-Binding Proteins; C498818:Sp6 protein, mouse; D014157:Transcription Factors; D011495:Histone-Lysine N-Methyltransferase; C521636:SETD2 protein, human; C587921:SETD2 protein, mouse; D012319:RNA Polymerase II