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Crp79p, like Mex67p, is an auxiliary mRNA export factor in Schizosaccharomyces pombe
Anjan G Thakurta1, William A Whalen, Jin Ho Yoon
1Basic Research Laboratory, National Cancer Institute, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, MD 20892, USA.
Abstract:
The export of mRNA from the nucleus to the cytoplasm involves interactions of proteins with mRNA and the nuclear pore complex. We isolated Crp79p, a novel mRNA export factor from the same synthetic lethal screen that led to the identification of spMex67p in Schizosaccharomyces pombe. Crp79p is a 710-amino-acid-long protein that contains three RNA recognition motif domains in tandem and a distinct C-terminus. Fused to green fluorescent protein (GFP), Crp79p localizes to the cytoplasm. Like Mex67p, Crp79-GFP binds poly(A)(+) RNA in vivo, shuttles between the nucleus and the cytoplasm, and contains a nuclear export activity at the C-terminus that is Crm1p-independent. All of these properties are essential for Crp79p to promote mRNA export. Crp79p import into the nucleus depends on the Ran system. A domain of spMex67p previously identified as having a nuclear export activity can functionally substitute for the nuclear export activity at the C-terminus of Crp79p. Although both Crp79p and spMex67p function to export mRNA, Crp79p does not substitute for all of spMex67p functions and probably is not a functional homologue of spMex67p. We propose that Crp79p is a nonessential mRNA export carrier in S. pombe.
Insights
Researchers identified Crp79p, a novel mRNA export factor in Schizosaccharomyces pombe. This protein facilitates mRNA export from the nucleus to the cytoplasm independently of Crm1p.
Area of Science:
- Molecular Biology
- Cell Biology
- Genetics
Background:
- mRNA export from the nucleus to the cytoplasm is a critical cellular process.
- This process involves complex interactions between mRNA-binding proteins and the nuclear pore complex.
- The identification of novel factors is key to understanding the intricacies of mRNA export pathways.
Purpose of the Study:
- To identify and characterize novel factors involved in mRNA export in Schizosaccharomyces pombe.
- To investigate the function and properties of the newly isolated protein, Crp79p.
- To compare Crp79p with known mRNA export factors like spMex67p.
Main Methods:
- Isolation of Crp79p using a synthetic lethal screen.
- Localization studies using green fluorescent protein (GFP) tagging.
- Analysis of poly(A)(+) RNA binding, nuclear-cytoplasmic shuttling, and nuclear import dependency on the Ran system.
- Functional complementation assays using domains of spMex67p.
Main Results:
- Crp79p, a 710-amino acid protein with RNA recognition motifs, was identified as a novel mRNA export factor.
- Crp79p localizes to the cytoplasm, binds poly(A)(+) RNA in vivo, shuttles between nucleus and cytoplasm, and possesses Crm1p-independent nuclear export activity.
- Crp79p's nuclear import is dependent on the Ran system, and its C-terminal export activity can be substituted by a domain from spMex67p.
Conclusions:
- Crp79p functions as a non-essential mRNA export carrier in S. pombe.
- While sharing some functions with spMex67p, Crp79p is not a functional homologue and does not substitute for all spMex67p functions.
- Crp79p represents a distinct pathway or component in the mRNA export machinery of S. pombe.