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

• Published in: Nucleic acids research Vol. 49; no. 1; pp. 322 - 339
• Main Authors: Wong, Lai, Vizeacoumar, Frederick S, Vizeacoumar, Franco J, Chelico, Linda
• Format: Journal Article
• Language: English
• Published: England Oxford University Press 11.01.2021
• Subjects: APOBEC-1 Deaminase - antagonists & inhibitors; APOBEC-1 Deaminase - metabolism; Binding, Competitive; Cell Line; Cell Line, Tumor; Cytidine - metabolism; Deamination; DNA Damage; DNA Replication; DNA, Neoplasm - chemistry; DNA, Neoplasm - metabolism; DNA, Single-Stranded - chemistry; DNA, Single-Stranded - metabolism; Facilitated Diffusion; Genome Integrity, Repair and; Histones - analysis; Humans; Lung - cytology; Lung - embryology; Neoplasm Proteins - antagonists & inhibitors; Neoplasm Proteins - metabolism; Neoplasms - genetics; Neoplasms - pathology; Organ Specificity; Recombinant Fusion Proteins - metabolism; Replication Protein A - genetics; Replication Protein A - metabolism; RNA, Messenger - biosynthesis; RNA, Messenger - genetics; RNA, Neoplasm - biosynthesis; RNA, Neoplasm - genetics
• ISSN: 0305-1048; 1362-4962
• DOI: 10.1093/nar/gkaa1201

Abstract Many APOBEC cytidine deaminase members are known to induce ‘off-target’ cytidine deaminations in 5′TC motifs in genomic DNA that contribute to cancer evolution. In this report, we characterized APOBEC1, which is a possible cancer related APOBEC since APOBEC1 mRNA is highly expressed in certain types of tumors, such as lung adenocarcinoma. We found a low level of APOBEC1-induced DNA damage, as measured by γH2AX foci, in genomic DNA of a lung cancer cell line that correlated to its inability to compete in vitro with replication protein A (RPA) for ssDNA. This suggests that RPA can act as a defense against off-target deamination for some APOBEC enzymes. Overall, the data support the model that the ability of an APOBEC to compete with RPA can better predict genomic damage than combined analysis of mRNA expression levels in tumors and analysis of mutation signatures. Graphical Abstract Graphical Abstract Depending on whether DNA replication is slowed or normal APOBECs must cycle through an excess of single-stranded (ss)DNA or compete with RPA to catalyze cytosine to uracil deaminations (C→U).