A role for TREX components in the release of spliced mRNA from nuclear speckle domains.
The TREX complex, which functions in mRNA export, is recruited to mRNA during splicing. Both the splicing machinery and the TREX complex are concentrated in 20-50 discrete foci known as nuclear speckle domains. In this study, we use a model system where DNA constructs are microinjected into HeLa cell nuclei, to follow the fates of the transcripts. We show that transcripts lacking functional splice sites, which are inefficiently exported, do not associate with nuclear speckle domains but are instead distributed throughout the nucleoplasm. In contrast, pre-mRNAs containing functional splice sites accumulate in nuclear speckles, and our data suggest that splicing occurs in these domains. When the TREX components UAP56 or Aly are knocked down, spliced mRNA, as well as total polyA+ RNA, accumulates in nuclear speckle domains. Together, our data raise the possibility that pre-mRNA undergoes splicing in nuclear speckle domains, before their release by TREX components for efficient export to the cytoplasm.
Dias
Anusha P
AP
Department of Cell Biology, Harvard Medical School, 240 Longwood Avenue, Boston, Massachusetts 02115, USA.
Dufu
Kobina
K
Lei
Haixin
H
Reed
Robin
R
D053487:DEAD-box RNA Helicases / Q000235:genetics; D006367:HeLa Cells; D006801:Humans; D017404:In Situ Hybridization, Fluorescence; D009687:Nuclear Proteins / Q000235:genetics; D034622:RNA Interference; D012322:RNA Precursors / Q000235:genetics; D012326:RNA Splicing / Q000235:genetics*; D012333:RNA, Messenger / Q000235:genetics*; D016601:RNA-Binding Proteins / Q000235:genetics; D014157:Transcription Factors / Q000235:genetics
C105242:ALYREF protein, human; D009687:Nuclear Proteins; D012322:RNA Precursors; D012333:RNA, Messenger; D016601:RNA-Binding Proteins; D014157:Transcription Factors; C487886:DDX39B protein, human; D053487:DEAD-box RNA Helicases