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Prp22, a DExH-box RNA helicase, plays two distinct roles in yeast pre-mRNA splicing
1Department of Microbiology, Cornell University Medical College, New York, NY 10021, USA. bschwer@mail.med.cornell.edu
Abstract:
In order to assess the role of Prp22 in yeast pre-mRNA splicing, we have purified the 130 kDa Prp22 protein and developed an in vitro depletion/reconstitution assay. We show that Prp22 is required for the second step of actin pre-mRNA splicing. Prp22 can act on pre-assembled spliceosomes that are arrested after step 1 in an ATP-independent fashion. The requirement for Prp22 during step 2 depends on the distance between the branchpoint and the 3' splice site, suggesting a previously unrecognized role for Prp22 in splice site selection. We characterize the biochemical activities of Prp22, a member of the DExH-box family of proteins, and we show that purified recombinant Prp22 protein is an RNA-dependent ATPase and an ATP-dependent RNA helicase. Prp22 uses the energy of ATP hydrolysis to effect the release of mRNA from the spliceosome. Thus, Prp22 has two distinct functions in yeast pre-mRNA splicing: an ATP-independent role during the second catalytic step and an ATP-requiring function in disassembly of the spliceosome.
Insights
Prp22 protein is crucial for yeast pre-mRNA splicing, aiding the second catalytic step independently of ATP. It also functions as an ATP-dependent RNA helicase, releasing mRNA during spliceosome disassembly.
Area of Science:
- Molecular Biology
- RNA Processing
- Gene Expression
Background:
- Pre-mRNA splicing is a fundamental process in eukaryotes, essential for generating mature messenger RNA (mRNA).
- The spliceosome, a large ribonucleoprotein complex, mediates pre-mRNA splicing through a series of dynamic conformational changes.
- Proteins belonging to the DExH-box family are known to play critical roles in RNA metabolism, including splicing.
Purpose of the Study:
- To elucidate the specific role of the DExH-box protein Prp22 in yeast pre-mRNA splicing.
- To characterize the biochemical activities of purified Prp22 and its functions in spliceosome dynamics.
- To investigate the ATP-dependence and splice site selection aspects of Prp22's function.
Main Methods:
- Purification of the 130 kDa Prp22 protein from yeast.
- Development of an in vitro depletion/reconstitution assay to study Prp22 function.
- Biochemical characterization of Prp22's ATPase and RNA helicase activities.
Main Results:
- Prp22 is essential for the second catalytic step of actin pre-mRNA splicing.
- Prp22 functions in an ATP-independent manner on post-step 1 arrested spliceosomes.
- Prp22 exhibits RNA-dependent ATPase and ATP-dependent RNA helicase activities, facilitating mRNA release from the spliceosome.
Conclusions:
- Prp22 possesses dual functions in yeast pre-mRNA splicing: an ATP-independent role in the second catalytic step and an ATP-dependent role in spliceosome disassembly.
- Prp22's involvement in step 2 is influenced by the distance between the branchpoint and the 3' splice site, suggesting a role in splice site selection.
- Prp22 utilizes ATP hydrolysis to release mRNA, highlighting its importance in the splicing cycle.