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V(D)J RECOMBINASE-MEDIATED DELETION OF THE HPRT GENE IN T-LYMPHOCYTES FROM ADULT HUMANS
Citation:
Fuscoe, J.C., L. Zimmerman, K. Harrington-Brock, L. Burnette, M. Moore, J. Nicklas, J. O'Neill, AND R. Albertini. V(D)J RECOMBINASE-MEDIATED DELETION OF THE HPRT GENE IN T-LYMPHOCYTES FROM ADULT HUMANS. U.S. Environmental Protection Agency, Washington, D.C., EPA/600/J-92/422 (NTIS PB93141216).
Description:
The hprt T-cell cloning assay allows the detection of mutations occurring in vivo in the hypoxanthine guanine phosphoribosyltransferase (hprt) gene of T-lymphocytes. e have shown previously that the illegitimate activity of V(D)J recombinase accounts for about 40% of the hprt mutations in T-lymphocytes of human newborns as measured with umbilical cord blood samples (Fuscoe et al., 1991). his mechanism results in deletion of hprt exons 2+3. n this report, we examined a collection of 314 HPRT-deficient clones derived from adult humans for evidence that the mutations were caused by this mechanism by analyzing exons 2+3 deletion mutations. NA sequence analysis of deletion breakpoint junctions whoed that eight of the mugations were the result of V(D)J recombinase activity. he frequency of the recombinase-mediated mutations was similar in the adults and newborns (2-4 x 10-7). owever, since the hprt mutant frequency is about 10-fold higher in the adult than in the newborn, the recombinase-mediated mutations account for only a few percent of teh adult mutations. hese mutations are likely to have occurred during early development and persist into adulthood. nregulated expression of V(D)J recombinase activity may be an important mechanism for genomic rearrangements in the genesis of cancer.