Nucleic Acids Research Advance Access originally published online on December 20, 2007
Nucleic Acids Research 2008 36(3):1037-1049; doi:10.1093/nar/gkm1120
| ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
Nucleic Acids Research, 2008, Vol. 36, No. 3 1037-1049
© 2007 The Author(s)
This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/2.0/uk/) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.
RNA |
Role of poly (A) tail as an identity element for mRNA nuclear export
Institute for Virus Research, Kyoto University, Kyoto 606-8507, Japan, and Core Research for Evolutional Science and Technology, Japan Science and Technology Agency, Tokyo 102-0075, Japan
*To whom correspondence should be addressed. Tel: +81 75 751 4018; Fax: +81 75 751 3992; Email: hitoohno{at}virus.kyoto-u.ac.jp
Received September 16, 2007. Revised November 4, 2007. Accepted December 1, 2007.
Different RNA species are rigorously discriminated and exported by distinct export factors, but this discrimination mechanism remains largely unknown. We previously showed, by RNA microinjection experiments, that intronless mRNAs are discriminated from U snRNAs based on their difference in RNA length. However, it was unclear how they are discriminated in the natural situation in which their nascent transcripts emerge progressively during transcription. We hypothesized that transcription from the corresponding promoters is important for this discrimination. Here we show that contrary to our hypothesis, the discrimination process was not significantly influenced by whether transcription occurred from an mRNA- versus a U snRNA-type promoter. Rather, the features of transcribed RNAs determined the RNA identity, consistent with our previous results of RNA microinjection. Moreover, we found that the poly (A) tail can function as an identity element for mRNA export. The presence of a poly (A) tail of an appropriate length committed otherwise short Pol II transcripts to the mRNA export pathway in a dominant manner, indicating that the poly (A) tail either contributes to increasing the RNA length or functions as a platform to recruit mRNA export factors. Our results reveal a novel function of the poly (A) tail in mRNA export.