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Title: DNA 3' pp 5' G de-capping activity of aprataxin: effect of cap nucleoside analogs and structural basis for guanosine recognition

DNA 3' pp 5'G caps synthesized by the 3'-PO 4/5'-OH ligase RtcB have a strong impact on enzymatic reactions at DNA 3'-OH ends. Aprataxin, an enzyme that repairs A5'pp5'DNA ends formed during abortive ligation by classic 3'-OH/5'-PO 4 ligases, is also a DNA 3' de-capping enzyme, converting DNAppG to DNA 3'p and GMP. By taking advantage of RtcB's ability to utilize certain GTP analogs to synthesize DNAppN caps, we show that aprataxin hydrolyzes inosine and 6-O-methylguanosine caps, but is not adept at removing a deoxyguanosine cap. We report a 1.5 Å crystal structure of aprataxin in a complex with GMP, which reveals that: (i) GMP binds at the same position and in the same anti nucleoside conformation as AMP; and (ii) aprataxin makes more extensive nucleobase contacts with guanine than with adenine, via a hydrogen bonding network to the guanine O6, N1, N2 base edge. Alanine mutations of catalytic residues His147 and His149 abolish DNAppG de-capping activity, suggesting that the 3' de-guanylylation and 5' de-adenylylation reactions follow the same pathway of nucleotidyl transfer through a covalent aprataxin-(His147)–NMP intermediate. Alanine mutation of Asp63, which coordinates the guanosine ribose hydroxyls, impairs DNAppG de-capping.
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  1. Sloan-Kettering Inst., New York, NY (United States). Molecular Biology Program
Publication Date:
Grant/Contract Number:
Accepted Manuscript
Journal Name:
Nucleic Acids Research
Additional Journal Information:
Journal Volume: 43; Journal Issue: 12; Journal ID: ISSN 0305-1048
Oxford University Press
Research Org:
Argonne National Lab. (ANL), Argonne, IL (United States). Advanced Photon Source (APS)
Sponsoring Org:
National Institutes of Health (NIH)
Country of Publication:
United States
OSTI Identifier: