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APOBEC1 cytosine deaminase activity on single-stranded DNA is suppressed by replication protein A

Lai Wong1, Frederick S Vizeacoumar2, Franco J Vizeacoumar2,3

  • 1Department of Biochemistry, Microbiology, and Immunology, University of Saskatchewan, Saskatoon, Saskatchewan S7N 5E5, Canada.

Nucleic Acids Research
|December 17, 2020
PubMed

Insights

APOBEC1, a cancer-related enzyme, causes minimal DNA damage in lung cancer cells. Its inability to bind single-stranded DNA (ssDNA) with replication protein A (RPA) suggests RPA protects against off-target deamination.

Area of Science:

  • Biochemistry
  • Genomics
  • Cancer Biology

Background:

  • APOBEC cytidine deaminases contribute to cancer evolution through off-target DNA deaminations.
  • APOBEC1 is implicated in cancer, with high mRNA expression in lung adenocarcinoma.

Purpose of the Study:

  • To characterize the DNA-damaging activity of APOBEC1.
  • To investigate the role of replication protein A (RPA) in modulating APOBEC1 activity.

Main Methods:

  • Assessed APOBEC1-induced DNA damage using γH2AX foci in a lung cancer cell line.
  • Measured the in vitro competition between APOBEC1 and RPA for single-stranded DNA (ssDNA).

Main Results:

  • APOBEC1 induced low levels of DNA damage in the tested lung cancer cell line.
  • APOBEC1 showed limited ability to compete with RPA for ssDNA binding.
  • RPA binding competition correlated with reduced APOBEC1-induced genomic damage.

Conclusions:

  • RPA can act as a protective mechanism against off-target deamination by certain APOBEC enzymes.
  • An APOBEC's ability to compete with RPA is a better predictor of genomic damage than mRNA expression or mutation signatures alone.

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