Cotranscriptional recruitment of the serine-arginine-rich (SR)-like proteins Gbp2 and Hrb1 to nascent mRNA via the TREX complex

doi:10.1073/pnas.0308663100

Cotranscriptional recruitment of the serine-arginine-rich (SR)-like proteins Gbp2 and Hrb1 to nascent mRNA via the TREX complex

^*Biochemie-Zentrum Heidelberg (BZH), University of Heidelberg, Im Neuenheimer Feld 328, 69120 Heidelberg, Germany; ^‡Department of Cell Biology, Harvard Medical School, Boston, MA 02115; and ^§Gene Center, University of Munich, Feodor-Lynen-Strasse 25, 81377 Munich, Germany

Communicated by Thomas Maniatis, Harvard University, Cambridge, MA, December 27, 2003 (received for review December 19, 2003)

Abstract

The TREX (transcription/export) complex couples transcription elongation to the nuclear export of mRNAs. In this article, we show that the poly(A)⁺ RNA-binding proteins Gbp2 and Hrb1, which resemble the serine-arginine-rich (SR) family of splicing factors found in higher eukaryotes, are specifically associated with the yeast TREX complex. We also show that Gbp2 and Hrb1 interact with Ctk1, a kinase that phosphorylates the C-terminal domain of RNA polymerase II during transcription elongation. Consistent with these findings, Gbp2 and Hrb1 associate with actively transcribed genes throughout their entire lengths. By using an RNA immunoprecipitation assay, we show that Gbp2 and Hrb1 also are bound to transcripts that are derived from these genes. We conclude that recruitment of the SR-like proteins Gbp2 and Hrb1 to mRNA occurs cotranscriptionally by means of association with the TREX complex and/or Ctk1.

Footnotes

↵ † To whom correspondence should be addressed. E-mail: cg5{at}ix.urz.uni-heidelberg.de.
Abbreviations: mRNP, messenger ribonucleoprotein; HA, hemagglutinin; TAP, tandem affinity-purification; ChIP, chromatin immunoprecipitation; CTD, C-terminal domain of RNA polymerase II; RNA-IP, RNA immunoprecipitation; RRM, RNA recognition motif; SR, serine-arginine-rich.