Fragile sites are loci of recurrent chromosome breakage in the genome. They are found in organisms ranging from bacteria to humans and are implicated in genome instability, evolution, and cancer. In budding yeast, inactivation of Mec1, a homolog of mammalian ATR, leads to chromosome breakage at fragile sites referred to as replication slow zones (RSZs). RSZs are proposed to be homologous to mam...

The purpose of this study was to characterize the clastogenic activity of 1,4-dihydroxy-5,8-bis [[(2-[(2-hydroxyethyl)amino] ethyl)amino]]-9, 10-anthracenedione (NSC 301739), an antitumor compound now under clinical investigation. Chromosome damage in Chinese hamster ovary cells in G2 phase was assayed directly by the technique of premature chromosome condensation, and this damage was compared ...

The objective of this study was to investigate whether G1 cells could enter S phase after premature chromosome condensation resulting from fusion with mitotic cells. HeLa cell synchronized in early G1, mid-G1, late G1, and G2 and human diploid fibroblasts synchronized in G0 and G1 phases were separately fused by use of UV-inactivated Sendai virus with mitotic HeLa cells. After cell fusion and p...

Cell fusion, premature chromosome condensation (PCC) and conventional cytogenetics were used to test whether the biochemical process of chromatin condensation-decondensation throughout the cell cycle, which depends on cyclin-regulated histone H1 kinase activity, affects the conversion of DNA damage into chromosome damage and determines intrinsic cell cycle-stage radiosensitivity. Results from t...

DNA double-strand break (DSB) repair and checkpoint control represent distinct mechanisms to reduce chromosomal instability. Ataxia telangiectasia (AT) cells have checkpoint arrest and DSB repair defects. Here, we examine the efficiency and interplay of ATM's G2 checkpoint and repair functions. Artemis cells manifest an identical and epistatic repair defect to AT but show proficient checkpoint ...