A B-cell-specific DNA Recombination Complex*
- From the ‡Basel Institute for Immunology, Postfach, CH-4005 Basel, Switzerland and the §Department of Microbiology and Immunology, University of California, San Francisco, California 94143-0670
Abstract
We have purified and biochemically characterized a multiprotein complex designated SWAP. In a DNA transfer assay, SWAP preferentially recombines (“swaps”) sequences derived from Ig heavy chain switch regions. We identified four of the proteins in the SWAP complex: B23 (nucleophosmin), C23 (nucleolin), poly(ADP-ribose) polymerase (PARP), and SWAP-70. The first three are proteins known to be present in most cells. B23 promotes single-strand DNA reannealing and the formation of joint molecules in a D-loop assay between homologous, but also between Sμ and Sγ sequences. SWAP-70 is a novel protein of 70 kDa. Its cDNA was cloned and sequenced, and the protein was overexpressed inEscherichia coli. SWAP-70 protein expression was found only in B lymphocytes that had been induced to switch to various Ig isotypes and in switching B-cell lines. SWAP-70 is a nuclear protein, has a weak affinity for DNA, binds ATP, and forms specific, high affinity complexes with B23, C23, and poly(ADP-ribose) polymerase. These findings are consistent with SWAP being the long elusive “switch recombinase” and with SWAP-70 being the specific recruiting element that assembles the switch recombinase from universal components.
Footnotes
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↵* This work was supported by National Institutes of Health Grant R01 GM37699 and by funds from the Markey Trust (to M. W.). The Basel Institute for Immunology was founded by and is supported by Hoffmann-La Roche, Basel, Switzerland.The costs of publication of this article were defrayed in part by the payment of page charges. The article must therefore be hereby marked “advertisement” in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.
The nucleotide sequence(s) reported in this paper has been submitted to the GenBank™/EMBL Data Bank with accession number(s) .
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↵¶ To whom correspondence should be addressed.
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↵1 The abbreviations used are: C, constant; H, heavy; bp, base pair(s); DTA, DNA transfer assay; ds, double-stranded; ss, single-stranded; nt, nucleotide(s); EPPS, 4-(2-hydroxyethyl)-1-piperazinepropanesulfonic acid; LPS, lipopolysaccharide; DTT, dithiothreitol; S, switch region; ConA, concanavalin A.
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↵2 R. Jessberger, G. de Murcia, and T. Borggrefe, unpublished observation.
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- Received January 2, 1998.
- Revision received March 21, 1998.
- The American Society for Biochemistry and Molecular Biology, Inc.
