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Association of mRNA Export Factor Yra1 with the C‐terminal Domain of RNA Polymerase II
Author(s) -
MacKellar April L,
Greenleaf Arno L
Publication year - 2009
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.23.1_supplement.666.3
Subject(s) - rna polymerase ii , ctd , messenger rna , transcription (linguistics) , transcription factor ii d , microbiology and biotechnology , biology , rna binding protein , rna , immunoprecipitation , phosphorylation , gene expression , rna polymerase , biochemistry , gene , promoter , oceanography , linguistics , philosophy , geology
The unique C‐terminal domain (CTD) of RNA polymerase II (Pol II) is composed of tandem heptad repeats of the consensus sequence YSPTSPS. This domain is subject to differential phosphorylation throughout the transcription cycle, mainly on serines 2 and 5 of the repeats. Proteins involved in transcription and RNA processing bind the CTD to localize to nascent pre‐mRNA during transcription. In S. cerevisiae , the mRNA export protein Yra1 (ALY/REF in metazoa) cotranscriptionally associates with mRNA and delivers it to the nuclear pore complex for export to the cytoplasm. Here we report that Yra1 binds in vitro to the elongating or hyperphosphorylated form of the CTD as judged by both Far Western and immobilized peptide binding assays. Using truncated versions of Yra1, we have determined that the C‐terminal segment of the protein is dispensable for phosphoCTD binding. PhosphoCTD binding also appears to involve non‐RRM residues of Yra1. In addition, co‐immunoprecipitation experiments with cell extracts demonstrate that the Yra1‐phosphoCTD interaction likely occurs in vivo . A model is proposed in which recruitment of Yra1 to the nacent mRNA is mediated by binding to and release from the phosphorylated forms of the CTD.