TIME SEQUENCE OF EVENTS LEADING TO CHROMOSOMAL ABERRATION FORMATION

Investigations have been carried out which have measured the influence of the repair polymerases on the yield of different types of chromoso mal aberrations. The studies were mainly concerned with the effect of inhibiting the poly merases on the yield of aberrations. The polymeras es fill in single strand regions, and the fact that their inhibition a ffects the yield of aberrations suggests that single strand lesions ar e influential in aberration formation. The results indicate that- 1. T here are two actions of polymerases in clastogenesis. One is in their involvement in a G2 repair system, in which the pair of chromatids is concerned, and which does not yield aberrations unless the inhibition is still operating when the cells enter mitosis. The second also opera tes in G, and S, and is such that when repair is inhibited, further da mage accrues. 2. The second action is affected by inhibiting polymeras e but operates even when the repair enzymes are active. 3. The product ion of chromosomal exchanges involves a series of reactions, some of w hich are reversible. 4. The time span over which the reactions occur i s much longer than has been envisaged previously (e.g., most of a cell cycle). (C) 1993 Wiley-Liss, Inc.