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A yeast protein that bidirectionally affects nucleocytoplasmic transport
D R Singleton1, S Chen, M Hitomi
1Institute of Pathology, Case Western Reserve University, Cleveland, Ohio 44106, USA.
Journal of Cell Science
|January 1, 1995
Summary
A temperature-sensitive Saccharomyces cerevisiae mutant (npl3) shows nuclear polyadenylated RNA accumulation at 37°C. This defect, potentially linked to RNA export, occurs before protein import issues, suggesting NPL3
Area of Science:
- Cell Biology
- Molecular Biology
- Genetics
Background:
- The NPL3/NOP3 gene in Saccharomyces cerevisiae encodes a nucleolar/nuclear protein.
- This protein has roles in nuclear protein import and rRNA maturation.
- NPL3 contains RNA recognition motifs (RRM) and a Gly-Arg repeat domain.
Purpose of the Study:
- To investigate the function of the NPL3 protein in nuclear transport.
- To characterize a temperature-sensitive mutant affecting RNA processing and localization.
- To determine the primary defect in the npl3 mutant.
Main Methods:
- In situ hybridization to detect polyadenylated RNA localization.
- Temperature-shift experiments to assess RNA and protein transport.
- Cloning and sequencing of the NPL3/NOP3 gene.
- Analysis of ultrastructural changes in the nucleoplasm.
Main Results:
- The npl3 mutant accumulates polyadenylated RNA in the nucleus at 37°C.
- A point mutation was identified in the RRM region of the ts NPL3 gene.
- The poly(A) tail length increased, and nucleoplasmic ultrastructure was altered at the restrictive temperature.
- RNA export defects were observed before significant nuclear import defects.
Conclusions:
- The NPL3 protein is involved in both nuclear RNA export and protein import.
- The primary defect in the npl3 mutant appears to be in RNA export.
- NPL3's dual role suggests a complex mechanism linking RNA and protein transport.