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DNA binding properties of human pol gammaB
José A Carrodeguas1, Kevin G Pinz, Daniel F Bogenhagen
1Department of Pharmacological Sciences, State University of New York at Stony Brook, Stony Brook, NY 11794-8651, USA.
The Journal of Biological Chemistry
|October 16, 2002
Summary
Human mitochondrial DNA polymerase accessory subunit (pol gammaB) binds double-stranded DNA longer than 40 bp. This binding requires two distinct sites on the pol gammaB dimer, suggesting a role in DNA replication or repair.
Area of Science:
- Molecular Biology
- Biochemistry
- Genetics
Background:
- Mitochondrial DNA polymerase accessory subunit (pol gammaB) is crucial for DNA replication and repair.
- Previous studies suggested pol gammaB binds single-stranded DNA.
- Recent structural analysis revealed a DNA-binding region in pol gammaB.
Purpose of the Study:
- To characterize the DNA-binding properties of human pol gammaB.
- To identify the specific DNA structures and sequences preferred by pol gammaB.
- To elucidate the structural requirements for pol gammaB DNA binding.
Main Methods:
- Oligonucleotide-based DNA-binding assays using double- and single-stranded DNA.
- Site-specific deletion mutagenesis of pol gammaB.
- Analysis of DNA-binding activity in heterodimeric pol gammaB constructs.
Main Results:
- Human pol gammaB preferentially binds double-stranded DNA longer than 40 base pairs.
- DNA binding is largely sequence-independent.
- Two distinct clusters of basic residues on opposite sides of the pol gammaB dimer are essential for DNA binding.
- A single DNA molecule must interact with both binding sites on the pol gammaB dimer.
Conclusions:
- Human pol gammaB binds double-stranded DNA, contrary to previous assumptions.
- The dimeric structure of pol gammaB and its two DNA-binding sites are critical for its function.
- While not essential for in vitro polymerase activity, pol gammaB's double-stranded DNA-binding ability likely plays a significant role in mitochondrial DNA replication or repair processes.