A B-cell-specific DNA recombination complex.
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 Smu and Sgamma sequences. SWAP-70 is a novel protein of 70 kDa. Its cDNA was cloned and sequenced, and the protein was overexpressed in Escherichia 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.
Borggrefe
T
T
Basel Institute for Immunology, Postfach, CH-4005 Basel, Switzerland.
Wabl
M
M
Akhmedov
A T
AT
Jessberger
R
R
D000255:Adenosine Triphosphate / Q000378:metabolism; D000595:Amino Acid Sequence; D000818:Animals; D001402:B-Lymphocytes / Q000378:metabolism*; D001483:Base Sequence; D003001:Cloning, Molecular; D004274:DNA, Recombinant / Q000235:genetics*; D004268:DNA-Binding Proteins / Q000235:genetics* / Q000378:metabolism; D004926:Escherichia coli / Q000235:genetics; D020662:Guanine Nucleotide Exchange Factors; D006358:Hot Temperature; D007700:Kinetics; D051379:Mice; D008810:Mice, Inbred C57BL; D015778:Minor Histocompatibility Antigens; D008969:Molecular Sequence Data; D009687:Nuclear Proteins / Q000235:genetics* / Q000378:metabolism; D000090243:Nucleophosmin; D010750:Phosphoproteins / Q000378:metabolism; D011065:Poly(ADP-ribose) Polymerases / Q000378:metabolism; D011485:Protein Binding; D011995:Recombination, Genetic
D004274:DNA, Recombinant; D004268:DNA-Binding Proteins; D020662:Guanine Nucleotide Exchange Factors; D015778:Minor Histocompatibility Antigens; C000715570:Npm1 protein, mouse; D009687:Nuclear Proteins; D010750:Phosphoproteins; C113365:Swap70 protein, mouse; C036825:phosphoprotein C23; D000090243:Nucleophosmin; D000255:Adenosine Triphosphate; D011065:Poly(ADP-ribose) Polymerases