Department of Biochemistry and Molecular Pharmacology; Schiffer Lab
Amino Acids, Peptides, and Proteins | Biochemistry | Enzymes and Coenzymes | Genetic Phenomena | Genetics and Genomics | Molecular Biology | Nucleic Acids, Nucleotides, and Nucleosides | Structural Biology
The APOBEC3 (A3) family of human cytidine deaminases is renowned for providing a first line of defense against many exogenous and endogenous retroviruses. However, the ability of these proteins to deaminate deoxycytidines in ssDNA makes A3s a double-edged sword. When overexpressed, A3s can mutate endogenous genomic DNA resulting in a variety of cancers. Although the sequence context for mutating DNA varies among A3s, the mechanism for substrate sequence specificity is not well understood. To characterize substrate specificity of A3A, a systematic approach was used to quantify the affinity for substrate as a function of sequence context, length, secondary structure, and solution pH. We identified the A3A ssDNA binding motif as (T/C)TC(A/G), which correlated with enzymatic activity. We also validated that A3A binds RNA in a sequence specific manner. A3A bound tighter to substrate binding motif within a hairpin loop compared to linear oligonucleotide, suggesting A3A affinity is modulated by substrate structure. Based on these findings and previously published A3A-ssDNA co-crystal structures, we propose a new model with intra-DNA interactions for the molecular mechanism underlying A3A sequence preference. Overall, the sequence and structural preferences identified for A3A leads to a new paradigm for identifying A3A's involvement in mutation of endogenous or exogenous DNA.
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DOI of Published Version
Sci Rep. 2018 May 14;8(1):7511. doi: 10.1038/s41598-018-25881-z. Link to article on publisher's site
Silvas TV, Hou S, Myint W, Nalivaika EA, Somasundaran M, Kelch BA, Matsuo H, Yilmaz NK, Schiffer CA. (2018). Substrate sequence selectivity of APOBEC3A implicates intra-DNA interactions. Open Access Articles. https://doi.org/10.1038/s41598-018-25881-z. Retrieved from https://escholarship.umassmed.edu/oapubs/3475
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