ATP-dependent recruitment of export factor Aly/REF onto intronless mRNAs by RNA helicase UAP56.
Loading of export factors onto mRNAs is a key step in gene expression. In vertebrates, splicing plays a role in this process. Specific protein complexes, exon junction complex and transcription/export complex, are loaded onto mRNAs in a splicing-dependent manner, and adaptor proteins such as Aly/REF in the complexes in turn recruit mRNA exporter TAP-p15 onto the RNA. By contrast, how export factors are recruited onto intronless mRNAs is largely unknown. We previously showed that Aly/REF is preferentially associated with intronless mRNAs in the nucleus. Here we show that Aly/REF could preferentially bind intronless mRNAs in vitro and that this binding was stimulated by RNA helicase UAP56 in an ATP-dependent manner. Consistently, an ATP binding-deficient UAP56 mutant specifically inhibited mRNA export in Xenopus oocytes. Interestingly, ATP activated the RNA binding activity of UAP56 itself. ATP-bound UAP56 therefore bound to both RNA and Aly/REF, and as a result ATPase activity of UAP56 was cooperatively stimulated. These results are consistent with a model in which ATP-bound UAP56 chaperones Aly/REF onto RNA, ATP is then hydrolyzed, and UAP56 dissociates from RNA for the next round of Aly/REF recruitment. Our finding provides a mechanistic insight into how export factors are recruited onto mRNAs.
Taniguchi
Ichiro
I
Institute for Virus Research, Kyoto University, Shogoin Kawahara-cho, Sakyo-ku, Kyoto 606-8507, Japan.
Ohno
Mutsuhito
M
D000251:Adenosine Triphosphatases / Q000378:metabolism; D000255:Adenosine Triphosphate / Q000378:metabolism*; D000818:Animals; D002457:Cell Extracts; D002467:Cell Nucleus / Q000378:metabolism; D006367:HeLa Cells; D006801:Humans; D006868:Hydrolysis; D007438:Introns / Q000235:genetics; D009154:Mutation / Q000235:genetics; D009687:Nuclear Proteins / Q000235:genetics / Q000378:metabolism*; D009865:Oocytes; D011485:Protein Binding; D020365:RNA Helicases / Q000235:genetics / Q000378:metabolism*; D012326:RNA Splicing / Q000235:genetics; D012333:RNA, Messenger / Q000235:genetics; D016601:RNA-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism*; D014981:Xenopus
D002457:Cell Extracts; D009687:Nuclear Proteins; D012333:RNA, Messenger; D016601:RNA-Binding Proteins; D014157:Transcription Factors; D000255:Adenosine Triphosphate; D000251:Adenosine Triphosphatases; D020365:RNA Helicases