MOUSE V(H)7183 RECOMBINATION SIGNAL SEQUENCES MEDIATE RECOMBINATION MORE FREQUENTLY THAN THOSE OF VHJ558

Mouse V-H gene segments are conventionally classified into 13 families on the basis of sequence similarity, The 7183 family lies close to th e 3' end of the locus and is preferentially used in BALB/c mice; J558, the largest family, lies close to the 5' end of the V-H stretch and i s preferentially used in C57BL/6 mice. To investigate whether differen tial effectiveness of the RSSs in the two families might contribute to the overusage of 7183 in the primary repertoire of BALB/c, we constru cted recombination substrates in which the recombination signal sequen ces (RSSs) of V-H segments 7183 and J558 compete with each other for a single RSS, DFL16.1, after transfection into two transformed cell lin es derived from C57BL/6 and two cell lines from BALB/c mice. In both s trains, the 7183 RSS was found to be preferentially used (83%), Thus, the 7183 RSS mediates recombination more frequently than does that of J558, and this preference must thereby influence the primary repertoir e, but the strain difference cannot be accounted for by a difference i n the RSSs.