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PIR1, a novel phosphatase that exhibits high affinity to RNA . ribonucleoprotein complexes
1Department of Genetics, Yale University School of Medicine, New Haven, Connecticut 06520, USA.
Abstract:
Protein tyrosine phosphatases are involved in the regulation of important cellular processes such as signal transduction, cell cycle progression, and tumor suppression. Here we report the cloning and characterization of PIR1, a novel member in the dual-specificity phosphatase subfamily of the protein tyrosine phosphatases. PIR1 also contains two stretches of arginine-rich sequences. We have shown that the recombinant PIR1 protein possessed an intrinsic phosphatase activity on phosphotyrosine-containing substrate. A unique feature of this phosphatase is that it binds directly to RNA in vitro with high affinity. In addition, we have found that PIR1 interacted with splicing factors 9G8 and SRp30C, possibly through an RNA intermediate during a yeast two-hybrid screen. PIR1 exhibited a nuclear-staining pattern that was sensitive to RNase A, but not to DNase I, suggesting that PIR1 in the cells are associated with RNA and/or ribonucleoprotein particles. Furthermore, a fraction of PIR1 showed a speckle-staining pattern that superimposed with that of the splicing factor, SC35. Taken together, our data suggest that PIR1 is a novel phosphatase that may participate in nuclear mRNA metabolism.
Insights
We discovered PIR1, a novel protein tyrosine phosphatase that binds RNA and interacts with splicing factors. This suggests PIR1 plays a role in nuclear mRNA metabolism.
Area of Science:
- Molecular Biology
- Biochemistry
- Cell Biology
Background:
- Protein tyrosine phosphatases (PTPs) regulate critical cellular functions, including signal transduction, cell cycle progression, and tumor suppression.
- The dual-specificity phosphatase subfamily of PTPs plays diverse roles in cellular regulation.
Purpose of the Study:
- To clone and characterize PIR1, a novel member of the dual-specificity phosphatase subfamily.
- To investigate the biochemical properties and cellular localization of PIR1.
Main Methods:
- Recombinant PIR1 protein expression and phosphatase activity assay.
- In vitro RNA binding assays.
- Yeast two-hybrid screening for interacting proteins.
- Cellular localization studies using microscopy and nuclease treatments.
Main Results:
- PIR1 exhibits intrinsic phosphatase activity on phosphotyrosine substrates.
- PIR1 binds directly to RNA in vitro with high affinity.
- PIR1 interacts with splicing factors 9G8 and SRp30C, potentially via RNA.
- PIR1 localizes to the nucleus and associates with RNA/ribonucleoprotein particles, with some co-localization with SC35 splicing factor speckles.
Conclusions:
- PIR1 is a novel RNA-binding phosphatase.
- PIR1 likely participates in nuclear mRNA metabolism and splicing processes.