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Evolution of RNA-binding specificity in T4 DNA polymerase
C C Wang1, A Pavlov, J D Karam
1Department of Biochemistry, SL43, Tulane University School of Medicine, New Orleans, Louisana 70112, USA.
The Journal of Biological Chemistry
|July 11, 1997
Summary
DNA polymerase from phage T4 (T4 gp43) acts as both a DNA replication enzyme and an RNA-binding repressor. Its dual functions and translational control are conserved in related phages, revealing insights into DNA replication regulation.
Area of Science:
- Molecular Biology
- Virology
- Biochemistry
Background:
- Bacteriophage T4 DNA polymerase (T4 gp43) is crucial for DNA replication.
- This enzyme exhibits dual functionality, acting as a DNA replicase and an RNA-binding translational repressor.
- Autogenous translational control regulates the biosynthesis of T4 gp43.
Purpose of the Study:
- To investigate the evolutionary relationship between the DNA-binding and RNA-binding functions of T4 gp43.
- To compare the translational control mechanisms of T4 gp43 with that of a related phage, RB69.
- To identify the protein regions responsible for RNA-binding specificity.
Main Methods:
- Phylogenetic analysis was employed to study the conservation of T4 gp43 functions.
- Comparative analysis of RNA targets and protein-RNA interactions between T4 and RB69 phages.
- Construction and study of T4-RB69 gp43 chimeras to map functional domains.
Main Results:
- Autogenous translational control of gp43 biosynthesis is conserved in phage RB69.
- Differences were observed in the RNA target sequence and structure, and in the RNA specificity of RB69 gp43 compared to T4 gp43.
- RB69 gp43 exhibits broader RNA-binding specificity, repressing operators from both T4 and RB69.
- RNA-binding specificity of T4 gp43 was mapped to a protein segment crucial for DNA binding and polymerase activity.
Conclusions:
- The dual nucleic acid-binding functions of T4 gp43 are evolutionarily conserved.
- RNA acts as a regulatory molecule influencing both the expression levels (dosage) and catalytic activity of this essential DNA replication enzyme.