Messenger RNAs are recruited for nuclear export during transcription

following transcription and processing, eukaryotic mRNAs are exported from the nucleus to the cytoplasm for translation. Here we present evidence that mRNAs are targeted for nuclear export cotranscriptionally. Combined mutati ons in the Saccharomyces cerevisiae hnRNP Npl3 and TATA-binding protein (TB P) block mRNA export, implying that cotranscriptional recruitment of Npl3 i s required for efficient export of mRNA. furthermore, Npl3 can be found in a complex with RNA Pol II, indicating that Npl3 associates with the transcr iption machinery. Finally, Npl3 is recruited to genes in a transcription de pendent manner as determined by chromatin immunoprecipitation. Another mRNA export factor, Yra1, also associates with chromatin cotranscriptionally bu t appears to be recruited at a later step. Taken together, our results sugg est that export factors are recruited to the sites of transcription to prom ote efficient mRNA export.