Adaptor Aly and co-adaptor Thoc5 function in the Tap-p15-mediated nuclear export of HSP70 mRNA.
In metazoans, nuclear export of bulk mRNA is mediated by Tap-p15, a conserved heterodimeric export receptor that cooperates with adaptor RNA-binding proteins. In this article, we show that Thoc5, a subunit of the mammalian TREX complex, binds to a distinct surface on the middle (Ntf2-like) domain of Tap. Notably, adaptor protein Aly and Thoc5 can simultaneously bind to non-overlapping binding sites on Tap-p15. In vivo, Thoc5 was not required for bulk mRNA export. However, nuclear export of HSP70 mRNA depends on both Thoc5 and Aly. Consistent with a function as a specific export adaptor, Thoc5 exhibits in vitro RNA-binding activity and is associated with HSP70 mRNPs in vivo as a component of the stable THO complex. Thus, through the combinatorial use of an adaptor (e.g., Aly) and co-adapter (e.g., Thoc5), Tap-p15 could function as an export receptor for different classes of mRNAs.
Katahira
Jun
J
Biomolecular Dynamics Laboratory, Graduate School of Frontier Biosciences, Osaka University, Yamadaoka, Suita, Osaka, Japan Japan. katahira@anat3.med.osaka-u.ac.jp
Inoue
Hitomi
H
Hurt
Ed
E
Yoneda
Yoshihiro
Y
D021581:Active Transport, Cell Nucleus; D000595:Amino Acid Sequence; D002460:Cell Line; D002467:Cell Nucleus / Q000378:metabolism*; D018840:HSP70 Heat-Shock Proteins / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D008958:Models, Molecular; D008969:Molecular Sequence Data; D009687:Nuclear Proteins / Q000378:metabolism*; D029543:Nucleocytoplasmic Transport Proteins / Q000502:physiology*; D012333:RNA, Messenger / Q000378:metabolism*; D016601:RNA-Binding Proteins / Q000378:metabolism* / Q000502:physiology*; D014157:Transcription Factors / Q000378:metabolism*
C105242:ALYREF protein, human; D018840:HSP70 Heat-Shock Proteins; C122111:NXF1 protein, human; C498546:NXT1 protein, human; D009687:Nuclear Proteins; D029543:Nucleocytoplasmic Transport Proteins; D012333:RNA, Messenger; D016601:RNA-Binding Proteins; C530378:THOC5 protein, human; D014157:Transcription Factors