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The Spt6 SH2 domain binds Ser2-P RNAPII to direct Iws1-dependent mRNA splicing and export.

Spt6 promotes transcription elongation at many genes and functions as a histone H3 chaperone to alter chromatin structure during transcription. We show here that mammalian Spt6 binds Ser2-phosphorylated (Ser2P) RNA polymerase II (RNAPII) through a primitive SH2 domain, which recognizes phosphoserine rather than phosphotyrosine residues. Surprisingly, a point mutation in the Spt6 SH2 domain (R1358K) blocked binding to RNAPIIo without affecting transcription elongation rates in vitro. However, HIV-1 and c-myc RNAs formed in cells expressing the mutant Spt6 protein were longer than normal and contained splicing defects. Ectopic expression of the wild-type, but not mutant, Spt6 SH2 domain, caused bulk poly(A)+ RNAs to be retained in the nucleus, further suggesting a widespread role for Spt6 in mRNA processing or assembly of export-competent mRNP particles. We cloned the human Spt6-interacting protein, hIws1 (interacts with Spt6), and found that it associates with the nuclear RNA export factor, REF1/Aly. Depletion of endogenous hIws1 resulted in mRNA processing defects, lower levels of REF1/Aly at the c-myc gene, and nuclear retention of bulk HeLa poly(A)+ RNAs in vivo. Thus binding of Spt6 to Ser2-P RNAPII provides a cotranscriptional mechanism to recruit Iws1, REF1/Aly, and associated mRNA processing, surveillance, and export factors to responsive genes.

Pubmed ID: 17234882


  • Yoh SM
  • Cho H
  • Pickle L
  • Evans RM
  • Jones KA


Genes & development

Publication Data

January 15, 2007

Associated Grants

  • Agency: NIAID NIH HHS, Id: AI044615-07

Mesh Terms

  • Amino Acid Substitution
  • Animals
  • Blotting, Far-Western
  • Cell Nucleus
  • DNA-(Apurinic or Apyrimidinic Site) Lyase
  • Exoribonucleases
  • Exosome Multienzyme Ribonuclease Complex
  • HIV-1
  • HeLa Cells
  • Humans
  • Mice
  • Nuclear Proteins
  • Phosphoserine
  • Point Mutation
  • Promoter Regions, Genetic
  • Proteins
  • RNA Polymerase II
  • RNA Splicing
  • RNA, Messenger
  • Recombinant Proteins
  • Transcription Factors
  • Transcriptional Activation
  • src Homology Domains