MOLECULAR ANALYSIS AND COMPARISON OF RADIATION-INDUCED LARGE DELETIONS OF THE HPRT LOCUS IN PRIMARY HUMAN SKIN FIBROBLASTS

Genetic alterations in gamma-ray- and alpha-particle-induced HPRT muta nts were examined by multiplex polymerase chain reaction (PCR) analysi s. A total of 39-63% of gamma-ray-induced and 31-57% of alpha-particle -induced mutants had partial or total deletions of the HPRT gene. The proportion of these deletion events was dependent on radiation dose, a nd at the resolution limits employed there were no significant differe nces between the spectra induced by equitoxic doses of ex particles (0 .2-0.4 Gy) and gamma rays (3 Gy). The molecular nature of the deletion s was analyzed by the use of sequence tagged site (STS) primers and PC R amplification as a ''probe'' for specific regions of the human X chr omosome within the Xq26 region. These STSs were closely linked and spa nned regions approximately 1.7 Mbp from the telomeric side and 1.7 Mbp from the centromeric side of the HPRT gene. These markers include: DX S53, 299R, DXS79, yH3L, 3/19, PR1, PR25, H2, yH3R, 1/44, 1/67, 1/1, DX S86, D8C6, DXS10 and DXS144. STS analyses indicated that the maximum s ize of total deletions in radiation-induced HPRT mutants can be greate r than 2.7 Mbp and deletion size appears to be dependent on radiation dose. There were no apparent differences in the sizes of the deletions induced by alpha particles or gamma rays. On the other hand, deletion s containing portions of the HPRT gene were observed to be 800 kbp or less, and the pattern of the partial deletion induced by alpha particl es appeared to be different from that induced by gamma rays. (C) 1996 by Radiation Research Society