| Abelson Murine Leukemia Virus (A-MuLV) transformed pre-B cell lines capable of undergoing immunodifferentiation events during growth in culture have been studied. Two A-MuLV transformed cell lines, BM18-4 and ABC-1, undergo immunoglobulin L-chain gene recombination during passage in tissue culture. BM18-4 cells are capable of (kappa) gene recombination whereas ABC-1 cells are capable of both (kappa) and (lamda) gene recombination. All ABC-1 cells that have (lamda) gene rearrangements also display recombined (kappa) alleles, supporting the hypothesis that (kappa) and (lamda) gene recombinations are initiated in developmentally ordered manner in maturing B-cells. However, analyses of the ABC-1 line indicate that pre-B cells which have initiated (lamda) gene recombination do not terminate (kappa) gene rearrangement.;Changes in local lg chromatin structure as evidenced by increased sensitivity to deoxyribonuclease I digestion occur during pre-B cell differentiation and correlate with the sequential pattern of lg gene recombination that apparently occurs as pre-B cells mature.;DNAasel sensitivity analyses of various RS (recombining sequence) DNA segments in pre-B cell lines indicate that RS recombinations appear to be associated with an "opening" of chromatin structure similar to that observed in lg gene rearranging pre-B cells. Recombined RS segments are infrequent among BM18-4 cells but common among ABC-1 cells, suggesting that RS recombinational events often occur in maturing pre-B cells just prior to the initiation of (lamda) gene rearrangements. These results are consistent with the hypothesis that RS recombination may be involved in the initiation of (lamda) gene assembly.;Analysis of the (lamda) gene recombinations that occur in the ABC-1 line indicate that the germline order of (lamda) gene segments is: 5'...V(lamda)2...J(lamda)2C(lamda)2-J(lamda)4C(lamda)4...V(lamda)1...J(lamda)3C(lamda)3-J(lamda)1C(lamda)1...3'. In addition, the frequencies of (lamda)1, (lamda)2, and (lamda)3 gene recombinations among ABC-1 cells are quite different than the frequencies of B-cells producing these chains in the mouse. |
