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Molecular mechanisms for the induction of chromosomal aberrations in CHO cells heated in S phase

1993; Wiley; Volume: 22; Issue: 4 Linguagem: Inglês

10.1002/em.2850220413

1098-2280

Rosemary Wong, William C. Dewey,

RNA Interference and Gene Delivery

Abstract Chromosomal aberrations are induced by heat only when Chinese hamster ovary cells are heated in S phase of the cell cycle. Studies on the hyperthermic inhibition of cellular DNA replication have indicated that four molecular aspects of DNA replication are affected after heating. New replicon initiation and DNA chain elongation are inhibited; the fork displacement rate is very sensitive to heat‐inactivation; and finally, there is almost a two‐fold increase in single‐stranded regions in the replicating DNA after heating. From a comparison of these altered processes between S phase cells and heated G 1 cells, which do not die from chromosomal aberrations, our current hypothesis involves 3 steps for the chromosomal aberration induction process. The first critical step is the persistent increase of single‐stranded regions in the replicating DNA. Then, we hypothesize that the second step is the creation of transient double strand breaks (DSBs) induced at sites opposite these regions by endogenous endonucleases. Finally, the third step requires that improper repair of these DSBs occurs from either nonrepair or misrepair which then leads to the final chromosomal aberrations seen in the first mitosis after treatment. We believe that this 3 step induction process is common for any cytotoxic agent that induces chromosomal aberrations after DNA replication has been inhibited. © 1993 Wiley‐Liss, Inc.