HETEROGENEITY IN THE MITOTIC CHECKPOINT CONTROL OF BALB 3T3 CELLS ANDA CORRELATION WITH GENE AMPLIFICATION PROPENSITY/

Chinese hamster ovary (and many rodent cell lines) transiently delay m itosis and progress into a second cell cycle without undergoing cytoki nesis when treated with Colcemid, whereas HeLaS3 (and most human cell lines) arrest permanently in mitosis. We have discussed these differen ces and their consequences for cell survival under cell cycle-perturbi ng conditions within the context of mitotic checkpoint control (Schimk e et al., Cold Spring Harbor Symp. Quant. Biol., 56: 417-425, 1991). H ere, we report studies with mouse BALB/3T3 cell populations which, by the criterion of response to Colcemid, constitute a heterogeneous popu lation with respect to mitotic checkpoint control. Clonal and subclona l populations retain population heterogeneity but with a bias for enri chment of cell populations that respond as do HeLaS3 cells. We have an alyzed clones for their propensity for gene amplification as assessed by a stepwise increment selection protocol in methotrexate and report that there are significant differences in amplification propensities t hat correlate with differences in mitotic checkpoint control propertie s.