Coordinate endonucleolytic 5' and 3' trimming of terminally blocked blunt DNA double-strand break ends by Artemis nuclease and DNA-dependent protein kinase
Year: 2008
Type: article
Abstract: Previous work showed that, in the presence of DNA-PK, Artemis slowly trims 3′phosphoglycolate-terminated blunt ends.To examine the trimming reaction in more detail, long internally labeled DNA substrates were treated with Artemis.In the absence of DNA-PK, Artemis catalyzed extensive 5′→3′ exonucleolytic resection of double-stranded DNA.This resection required a 5′-phosphate but did not require ATP, and was accompanied by endonucleolytic cleavage of the resulting 3′ overhang.In the presence of DNA-PK, Artemismediated trimming was more limited, was ATP-dependent, and did not require a 5′-phosphate.For a blunt end with either a 3′-phosphoglycolate or 3′-hydroxyl terminus, endonucleolytic trimming of 2-4 nucleotides from the 3′-terminal strand was accompanied by trimming of 6 nucleotides from the 5′-terminal strand.The results suggest that autophosphorylated DNA-PK suppresses the exonuclease activity of Artemis toward blunt-ended DNA, and promotes slow and limited endonucleolytic trimming of the 5′-terminal strand, resulting in short 3′ overhangs that are trimmed endonucleolytically.Thus, Artemis and DNA-PK can convert terminally blocked DNA ends of diverse geometry and chemical structure to a form suitable for polymerasemediated patching and ligation, with minimal loss of terminal sequence.Such processing could account for the very small deletions often found at DNA double-strand break repair sites.
Author: Steven M. Yannone
Language: English
Topic: DNA Repair Mechanisms
Subfield: Molecular Biology
Domain: Life Sciences
Open Access status: green
OpenAlex ID: W2211025981