Messenger RNAs are recruited for nuclear export during transcription
Elissa P. Lei, Heike Krebber,1 and Pamela A. Silver2
1 Present address: Philipps-University Marburg, Institute for Molecular Biology and Tumor Research (IMT), 35037 Marburg, Germany.
2 Corresponding author
Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School and Dana-Farber Cancer Institute, Boston, Massachusetts 02115, USA
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 mutations in the Saccharomyces cerevisiae hnRNP Npl3 and TATA-binding protein (TBP) block mRNA export, implying that cotranscriptional recruitment of Npl3 is required for efficient export of mRNA. Furthermore, Npl3 can be found in a complex with RNA Pol II, indicating that Npl3 associates with the transcription machinery. Finally, Npl3 is recruited to genes in a transcription dependent manner as determined by chromatin immunoprecipitation. Another mRNA export factor, Yra1, also associates with chromatin cotranscriptionally but appears to be recruited at a later step. Taken together, our results suggest that export factors are recruited to the sites of transcription to promote efficient mRNA export.
[Key Words: Transcription; mRNA export; chromatin IP; RNA polymerase II; Npl3; Yra1]
Source: Genes and Development, Vol. 15, No. 14, pp. 1771-1782, July 2001