THE G(1) PROCESS IN PHA-STIMULATED HUMAN- LYMPHOCYTES AND THE APPEARANCE OF RADIATION-INDUCED CHROMOSOME-ABERRATIONS

Experimental evidence for the existence of local spontaneous DNA synth esis in PHA-stimulated human lymphocytes at the G(1) phase (G(1) proce ss) is presented. This process is associated with the appearance of si ngle-stranded DNA breaks and their subsequent reparation. DNA sequence s involved in the G(1) process were characterized in terms of their nu cleotide composition and association with the nuclear matrix. It was s hown that the G(1) process occurs in chromosome regions in which radia tion-induced exchange-type chromosome aberrations arise. The results o f the study are regarded as evidence in favor of a molecular version o f the primary contact theory of chromosomal mutagenesis. A possible ro le of G(1) process disturbances in pathogenesis of chromosome instabil ity syndromes in humans is discussed.