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Splicing proofreading at 5' splice sites by ATPase Prp28p

Fei Yang1, Xiu-Ye Wang, Zhi-Min Zhang

  • 1Key Laboratory of Insect Developmental and Evolutionary Biology, Institute of Plant Physiology and Ecology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai 200032, China.

Nucleic Acids Research
|March 7, 2013
PubMed

Insights

WT-Prp28p proofreads 5' splice sites (SS) to ensure accurate mRNA generation. Mutations in Prp28p reduce its activity, enhancing the splicing of suboptimal 5'SS, revealing its critical role in splicing fidelity.

Area of Science:

  • Molecular Biology
  • Genetics
  • RNA Processing

Background:

  • Accurate pre-mRNA splicing is essential for producing functional messenger RNA (mRNA).
  • The precise selection of the 5' splice site (SS) is a critical step in splicing, but the mechanisms ensuring this accuracy are not fully understood.
  • The protein Prp28p is known to be involved in spliceosome assembly and function.

Purpose of the Study:

  • To investigate the role of Prp28p in the fidelity of 5' splice site selection during pre-mRNA splicing.
  • To identify specific mutations in Prp28p that affect its proofreading activity.
  • To elucidate the molecular mechanisms by which Prp28p ensures accurate splice site recognition.

Main Methods:

  • Yeast genetic screens to isolate prp28 alleles with altered splicing activity.
  • Analysis of splicing efficiency for suboptimal 5'SS substrates.
  • Biochemical assays to assess RNA-binding activity of Prp28p variants.
  • Functional characterization of a specific Prp28p mutant (E404K) in yeast and Drosophila cells.

Main Results:

  • Yeast genetic screens identified prp28 alleles that improve splicing of suboptimal 5'SS, indicating Prp28p's proofreading function.
  • Prp28p proofreading depends on competition with the stability of the 5'SS:U6 snRNA duplex, not the 5'SS:U1 snRNA duplex.
  • A specific mutation (E404K) in the Prp28p linker region reduced RNA-binding activity and enhanced splicing of suboptimal substrates, suggesting decreased proofreading.
  • The E404 residue is crucial for high splicing activity in both yeast and Drosophila.

Conclusions:

  • Wild-type Prp28p acts as a proofreader, rejecting incorrect 5' splice sites.
  • The subdomain linker of Prp28p plays a vital role in both splicing efficiency and 5'SS proofreading across different species.
  • Decreased Prp28p activity allows more time for suboptimal 5'SS to pair with U6 snRNA, potentially reducing splicing fidelity.

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