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Molecular and Cellular Biology, June 1999, p. 4159-4166, Vol. 19, No. 6
Howard Hughes Medical Institute and Section
of Immunobiology, Yale University School of Medicine, New Haven,
Connecticut 06520-8011
Received 14 January 1999/Returned for modification 19 February
1999/Accepted 15 March 1999
The lymphoid cell-specific proteins RAG1 and RAG2 initiate V(D)J
recombination by cleaving DNA adjacent to recombination signals, generating blunt signal ends and covalently sealed, hairpin coding ends. A critical next step in the reaction is opening of the hairpins, but the factor(s) responsible has not been identified and had been
thought to be a ubiquitous component(s) of the DNA repair machinery.
Here we demonstrate that RAG1 and RAG2 possess an intrinsic single-stranded nuclease activity capable of nicking hairpin coding ends at or near the hairpin tip. In Mn2+, a synthetic
hairpin is nicked 5 nucleotides (nt) 5' of the hairpin tip, with more
distant sites of nicking suppressed by HMG2. In Mg2+,
hairpins generated by V(D)J cleavage are nicked whereas synthetic hairpins are not. Cleavage-generated hairpins are nicked at the tip and
predominantly 1 to 2 nt 5' of the tip. RAG1 and RAG2 may therefore be
responsible for initiating the processing of coding ends and for the
generation of P nucleotides during V(D)J recombination.
0270-7306/99/$04.00+0
Copyright © 1999, American Society for Microbiology. All rights reserved.
DNA Hairpin Opening Mediated by the RAG1 and
RAG2 Proteins
*
Corresponding author. Mailing address: Howard Hughes
Medical Institute and Section of Immunobiology, Yale University School of Medicine, 310 Cedar St., P.O. Box 208011, New Haven, CT 06520-8011. Phone: (203) 737-2255. Fax: (203) 737-1764 or (203) 737-1765. E-mail:
david.schatz{at}yale.edu.
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