Structural modifications induced in Chinese hamster V79--E chromosomes by prefixation treatment in vitro with the AT-specific agents netropsin, distamycin A, and Hoechst 33258.

Abstract

Prefixation treatment of Chinese hamster V79-E cells with the AT-specific agents netropsin, distamycin A and Hoechst 33258 produced a dose- and time-dependent alteration of chromosome morphology. Compared to control cultures the chromosomes appear less condensed and revealed, after Giemsa staining, a non-random pattern of light and dark segments. It was found that the induced banding pattern corresponded for the three agents tested. Some of the darkly stained regions coincided with the extracentromeric C-bands seen in the karyotype of this cell strain, suggesting these areas to be GC-rich heterochromatin. The binding specifity and the mode of action of netropsin, distamycin A and Hoechst 33258 in DNA and chromatin suggest that the structural modifications induced depend on the amount of AT-base clusters in specific regions. Differential deprivation of chromosomal proteins might also contribute to the observed differences in stainability of chromosome segments. Attempts to induce elongations or banding patterns by prefixation treatment with the GC-specific agents actinomycin D and oligomycin were unsuccessful.