Characterization of the roles of TRAP150 in nuclear mRNA processing
Date Issued
2010
Date
2010
Author(s)
Lee, Kuo-Ming
Abstract
TRAP150 was initially identified as a subunit of the transcription coactivator TRAP/Mediator complex. In addition, TRAP150 has also been detected as a component of the spliceosome, suggesting its role in pre-mRNA splicing. We recently reported that TRAP150 colocalizes with splicing factors in nuclear speckles. TRAP150 is not only required for pre-mRNA splicing in vivo, but also substantially activates splicing when overexpressed. We found that TRAP150 remains bound to the spliced mRNA after splicing and accordingly interacts directly with several components of the exon junction complex and the mRNA export receptor TAP. This observation suggests that TRAP150 has a post-splicing function. When tethered to a precursor mRNA, TRAP150 could induce degradation of the spliced mRNA. However, in contrast to the canonical nonsense-mediated decay, TRAP150-mediated mRNA decay is translation independent and occurs in the nucleus. TRAP150 activates pre-mRNA splicing and mRNA degradation via distinct domains, but how it exactly acts in these two events is not yet clear. We recently screened for TRAP150-interacting proteins and found that TRAP150 also associated with polyadenylation factors. Therefore, TRAP150 may function in coordinating different steps of nuclear mRNA processing and perhaps target aberrantly processed mRNAs for degradation.
Subjects
pre-mRNA splicing
mRNA decay
spliceosome
nuclear mRNA processing
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