NORMAL V(D)J CODING JUNCTION FORMATION IN DNA LIGASE-I DEFICIENCY SYNDROMES

Bloom syndrome and a clinically related syndrome represented by the ce ll line 46BR have been associated with reduction in DNA ligase I activ ity. In-these syndromes, DNA ligase I deficiency severely impairs the development and function of the immune system. We undertook analysis o f DNA ligase I-deficient cells to determine whether the observed immun e deficiency is attributable to a perturbation in the process of V(D)j recombination. V(D)J recombination in Bloom syndrome cell lines and 4 6BR was examined by a transient transfection assay. No effect on the f idelity of coding and signal junction formation in DNA ligase I-defici ent cells was observed. The frequency of V(D)J recombination in DNA li gase I-deficient cells was also examined using recombination substrate s modified to function in human cells. Similar recombination frequenci es were observed in normal and DNA ligase I-deficient cells, demonstra ting that the efficiency of the V(D)J recombination process is unaffec ted by alterations in DNA ligase I activity. Rearranged immunoglobulin loci from Bloom syndrome cell lines and patient material were molecul arly cloned by an inverse polymerase chain reaction strategy which sho uld be applicable to a variety of human immunodeficiency syndromes and were indistinguishable from those found in normal bone marrow samples . Our data argue that the immune system defects associated with DNA li gase I deficiency do not result from perturbation of the V(D)J recombi nation pathway.