Our group has been interested in the pre-mRNA splicing and insect developmental biology. Currently we are investigating the sex determination cascade in Bombyx. mori,, which regulated by alternative splicing, and the function of RNA-dependent ATPases (or RNA helicases) during the spliceosome assembly pathway. We expect to address several other important developmental processes in insect systems which are regulated by alternative splicing.

Pricipal Investigator: Dr. Yong-Zhen Xu, Professor. Email: yzxu@sippe.ac.cn
Staff: Dr. Xin-Yan Xu, Research Assistant; Jia Pu, Research Intern
Graduate Students: Fei Yang; Wei Shao; Xiu-Ye Wang

Competition between the ATPase Prp5 and Branch Region–U2 snRNA Pairing Modulates the Fidelity of Spliceosome Assembly
Both accuracy and flexibility in splice site selection are needed to generate functional mRNAs and to allow for the extensive alternative splicing observed in metazoans, but how such flexibility is achieved is not clear. ATPase-facilitated steps during spliceosome function have been postulated to afford opportunities for kinetic proof-reading. Spliceosome assembly requires the ATPase Prp5p, whose activity might thus impact fidelity during initial intron recognition. Using alanine mutations in S. cerevisiae Prp5p we identified a suboptimal intron whose splicing could be improved by altered Prp5p activity, then, using this intron, screened for potent prp5 mutants. These prp5 alleles specifically alter branch region selectivity, with improved splicing in vivo of suboptimal substrates correlating with reduced ATPase activity in vitro for a series of mutants in ATPase motif III (SAT). Because these effects are abrogated by compensatory U2 snRNA mutations or other changes that increase branch region–U2 pairing, these results explicitly link a fidelity event with a defined physical structure, the branch region–U2 snRNA duplex, and provide strong evidence that progression of the splicing pathway requires branch region–U2 snRNA pairing prior to Prp5p-facilitated conformational change.

Publications:

1. Xu, YZ, and Query, CC. (2007) Competition between the ATPase Prp5 and branch region-U2 snRNA pairing modulates the fidelity of spliceosome assembly. Molecular Cell 28: 838-849.

2. Xu, YZ, Newnham, CM, Kameoka, S, Huang, T, Konarska, MM and Query, CC. (2004) Prp5 bridges U1 and U2 snRNPs and enables stable U2 snRNP association with intron RNA. EMBO Journal 23: 376-385.

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