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Proc Natl Acad Sci U S A. 2013 Dec 17;110(51):20437-42. doi: 10.1073/pnas.1314289110. Epub 2013 Nov 11.

Rewriting the rules for end joining via enzymatic splicing of DNA 3'-PO4 and 5'-OH ends.

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Molecular Biology Program, Sloan-Kettering Institute, New York, NY 10065.


There are many biological contexts in which DNA damage generates "dirty" breaks with 3'-PO4 (or cyclic-PO4) and 5'-OH ends that cannot be sealed by DNA ligases. Here we show that the Escherichia coli RNA ligase RtcB can splice these dirty DNA ends via a unique chemical mechanism. RtcB transfers GMP from a covalent RtcB-GMP intermediate to a DNA 3'-PO4 to form a "capped" 3' end structure, DNA3'pp5'G. When a suitable DNA 5'-OH end is available, RtcB catalyzes attack of the 5'-OH on DNA3'pp5'G to form a 3'-5' phosphodiester splice junction. Our findings unveil an enzymatic capacity for DNA 3' capping and the sealing of DNA breaks with 3'-PO4 and 5'-OH termini, with implications for DNA repair and DNA rearrangements.

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