RESUMO
We investigated recruitment of the yeast mRNA export factor Yra1 to the transcription elongation complex (TEC). Previously, the Sub2 helicase subunit of TREX was proposed to recruit Yra1. We report that Sub2 is dispensable for Yra1 recruitment, but the cleavage/polyadenylation factor, CF1A, is required. Yra1 binds directly to the Zn finger/Clp1 region of Pcf11, the pol II CTD-binding subunit of CF1A, and this interaction is conserved between their human homologs. Tethering of Pcf11 to nascent mRNA is sufficient to enhance Yra1 recruitment. Interaction with Pcf11 can therefore explain Yra1 binding to the TEC independently of Sub2. We propose that after initially binding to Pcf11, Yra1 is transferred to Sub2. Consistent with this idea, Pcf11 binds the same regions of Yra1 that also contact Sub2, indicating a mutually exclusive interaction. These results suggest a mechanism for cotranscriptional assembly of the export competent mRNP and for coordinating export with 3' end processing.
Assuntos
Proteínas Nucleares/metabolismo , Processamento de Terminações 3' de RNA/genética , RNA Mensageiro/metabolismo , Proteínas de Ligação a RNA/metabolismo , Proteínas de Saccharomyces cerevisiae/metabolismo , Fatores de Poliadenilação e Clivagem de mRNA/metabolismo , Transporte Ativo do Núcleo Celular/fisiologia , Adenosina Trifosfatases/genética , Adenosina Trifosfatases/metabolismo , Sequência de Aminoácidos , Sítios de Ligação , Modelos Biológicos , Dados de Sequência Molecular , Proteínas Nucleares/genética , Transporte de RNA , Proteínas de Ligação a RNA/genética , Ribonucleoproteínas/metabolismo , Proteínas de Saccharomyces cerevisiae/genética , Fatores de Poliadenilação e Clivagem de mRNA/genéticaRESUMO
Histone H3 Lys4 trimethylation (H3-K4me3) is a conserved mark of actively transcribed chromatin. Using a conditional mutant of the yeast H3-K4 methyltransferase, Set1p, we demonstrate rapid turnover of H3-K4me3 and H3-K4me2 in vivo and show this process requires Yjr119Cp, of the JARID1 family of JmjC proteins. Ectopic overexpression of mouse Jarid1B, a Yjr119Cp homolog, greatly diminished H3-K4me3 and H3-K4me2 in HeLa cells, suggesting these proteins function as K4 demethylases in vivo.