REARRANGEMENT OF A VH-ASSOCIATED LINE-1 ELEMENT WITH THE EXPRESSED IGH CLUSTER IN A MURINE MYELOMA CELL-LINE

The MPC11 mouse myeloma cell line (IgC2b kappa) has yielded numerous v ariants in Ig heavy-chain production. One such variant, E5.7A14, fails to produce gamma(2)b heavy chain but still produces kappa light chain . Comparison of the restriction maps of E5.7A14 and MPC11 has shown th at in E5.7A14, the expressed MPC11VH gene has been deleted and replace d by a different DNA segment. Cloning and sequencing of the rearranged heavy-chain gene has identified the new DNA segment as a virtually fu ll-length LINE-1 element that, in germ line, apparently lies in a inve rted transcriptional orientation downstream of a previously unknown me mber (pseudogene) of the VH3609 gene family. The LINE-1 rearrangement was associated with an inversion of a 2-kb segment of the J-C gamma(2) b intron and a deletion of switch sequences. The nature of the rearran gements and the sequences at recombination and inversion breakpoints s uggest that the rearrangement event was mediated via class switch mech anisms. This is one of a limited number of reports that both character izes a LINE rearrangement and localizes the germ-line origin of the pa rticular LINE element involved.