ANALYSIS OF RESTRICTION ENZYME-INDUCED CHROMOSOME-ABERRATIONS IN THE INTERSTITIAL TELOMERIC REPEAT SEQUENCES OF CHO AND CHE CELLS BY FISH

The interstitial telomeric sequences have been suggested to be more su sceptible to chromosome breakage and rejoining. In the present study, we tested this possibility by analysing the behaviour of intra-chromos omal telomeric sequences in restriction enzyme-treated CHO and CHE cel ls. These cell lines show large blocks of internal telomeric repeats a djacent to the centromeric regions of the chromosomes. In CHO cells, ( TTAGGG)n repeats are localised only near the centromeric regions of ma ny of the chromosomes while in CHE cells the telomeric repeat sequence s are found at both the terminal and centromeric regions of the chromo somes. In CHO cells, 26% of the total aberrations induced by AluI and 22% of those induced by Hinfl were found to be involved with internal telomeric repeat sequences. In CHE cells, which possess telomeric repe ats at both the terminal and interstitial regions, 39% of the aberrati ons induced by AluI and PuuII showed telomeric repeat signals. The pro portion of acentric fragments with a telomeric repeat signal was highe r in CHE than in CHO cells. Some of the damaged cells displayed an int ense signal indicating the possible amplification of these repeats by telomerase. These results are in accordance with the suggestion that n on-telomeric locations of telomeric repeat sequences are more prone to chromosome breakage and misrepair.