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Polyribonucleotide phosphorylase is a double-stranded DNA-binding protein
P Zhang1, J L Vigne, S H Mellon
1Department of Obstetrics, Gynecology and Reproductive Sciences, The Reproductive Endocrinology Center, University of California, San Francisco 94143-0556, USA.
Abstract:
Polyribonucleotide phosphorylase (PNPase) is one of the critical components of the E. coli RNA degradosome, which consists of both PNPase and endoribonuclease RNase E. The function of this complex is to control the rate of mRNA degradation. The PNPase possesses two enzymatic activities, namely 3'-5' processive exoribonuclease activity and 5'-3' RNA polymerase activity. In the present study, we used conventional chromatography to purify an E. coli protein that binds to a specific double-stranded DNA sequence. Microsequencing of the purified protein showed that this DNA-binding protein was PNPase. Our data further demonstrate that PNPase binds to DNA in a sequence-specific manner. These data suggest that PNPase may have previously unappreciated DNA-related functions in addition to its known role in mRNA degradation.
Insights
Polyribonucleotide phosphorylase (PNPase) in E. coli binds DNA specifically. This suggests PNPase has uncharacterized DNA-related functions beyond its known role in mRNA degradation.
Area of Science:
- Molecular Biology
- Biochemistry
- Genetics
Background:
- Polyribonucleotide phosphorylase (PNPase) is a key enzyme in the E. coli RNA degradosome, involved in mRNA degradation.
- The RNA degradosome complex comprises PNPase and endoribonuclease RNase E, regulating mRNA decay rates.
- PNPase exhibits both 3'-5' exoribonuclease and 5'-3' RNA polymerase activities.
Purpose of the Study:
- To identify and characterize E. coli proteins that bind to specific double-stranded DNA sequences.
- To investigate potential novel DNA-binding functions of PNPase.
Main Methods:
- Conventional chromatography was employed for protein purification.
- Microsequencing was utilized to identify the purified protein.
- DNA-binding assays were performed to assess sequence specificity.
Main Results:
- A protein that binds to a specific double-stranded DNA sequence was purified from E. coli.
- Microsequencing identified the purified protein as PNPase.
- PNPase demonstrated sequence-specific DNA-binding capabilities.
Conclusions:
- PNPase binds to DNA in a sequence-specific manner.
- These findings indicate that PNPase may possess previously unrecognized DNA-related functions.
- The study expands the known functional repertoire of PNPase beyond its established role in RNA metabolism.