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Mutations in VPS16 and MRT1 stabilize mRNAs by activating an inhibitor of the decapping enzyme
S Zhang1, C J Williams, K Hagan
1Department of Molecular Genetics, Robert Wood Johnson Medical School, New Jersey, USA.
Abstract:
Decapping is a rate-limiting step in the decay of many yeast mRNAs; the activity of the decapping enzyme therefore plays a significant role in determining RNA stability. Using an in vitro decapping assay, we have identified a factor, Vps16p, that regulates the activity of the yeast decapping enzyme, Dcp1p. Mutations in the VPS16 gene result in a reduction of decapping activity in vitro and in the stabilization of both wild-type and nonsense-codon-containing mRNAs in vivo. The mrt1-3 allele, previously shown to affect the turnover of wild-type mRNAs, results in a similar in vitro phenotype. Extracts from both vps16 and mrt1 mutant strains inhibit the activity of purified Flag-Dcp1p. We have identified a 70-kDa protein which copurifies with Flag-Dcp1p as the abundant Hsp70 family member Ssa1p/2p. Intriguingly, the interaction with Ssa1p/2p is enhanced in strains with mutations in vps16 or mrt1. We propose that Hsp70s may be involved in the regulation of mRNA decapping.
Insights
Yeast decapping enzyme activity, crucial for RNA stability, is regulated by Vps16p. Mutations in VPS16 and mrt1 reduce decapping, stabilizing mRNA, and implicate Hsp70s in this process.
Area of Science:
- Molecular Biology
- Yeast Genetics
- RNA Metabolism
Background:
- mRNA decapping is a critical, rate-limiting step in messenger RNA decay.
- The activity of the decapping enzyme directly influences RNA stability.
- Understanding the regulation of decapping is key to comprehending gene expression control.
Purpose of the Study:
- To identify factors regulating the activity of the yeast decapping enzyme, Dcp1p.
- To investigate the role of Vps16p and Mrt1p in mRNA decapping and stability.
- To explore the potential involvement of heat shock proteins in mRNA decapping regulation.
Main Methods:
- In vitro decapping assays were employed to measure enzyme activity.
- Genetic mutations in VPS16 and mrt1 alleles were analyzed.
- Co-purification studies identified proteins interacting with the decapping enzyme.
- Analysis of mRNA stability in vivo for wild-type and mutant strains.
Main Results:
- Vps16p was identified as a regulator of yeast decapping enzyme (Dcp1p) activity.
- Mutations in VPS16 and mrt1 decreased in vitro decapping activity.
- Mutant strains exhibited stabilized wild-type and nonsense-containing mRNAs in vivo.
- Hsp70 family member Ssa1p/2p was found to copurify with Dcp1p, with enhanced interaction in vps16 and mrt1 mutants.
Conclusions:
- Vps16p and Mrt1p play significant roles in regulating yeast mRNA decapping.
- Hsp70 proteins, specifically Ssa1p/2p, are likely involved in the regulation of mRNA decapping.
- These findings shed light on novel mechanisms controlling RNA stability and turnover in yeast.