0000000000595850
AUTHOR
Stefania Bonatti
Modulation of induced reversion frequency by nucleotide pool imbalance as a tool for mutant characterization.
Addition of thymidine (TdR) or deoxycytidine (CdR) to the culture medium during posttreatment incubation affected the frequency of mutagen-induced reversion in three hypoxanthine-guanine phosphoribosyl transferase-deficient mutants of V79 Chinese hamster cells. With two of the mutants (E20 and I3), reversions induced by N-ethylnitrosourea, ethyl methanesulfonate, and methyl methanesulfonate were enhanced by TdR and were either decreased (E20) or not affected (I3) by CdR. With the third mutant (E21), alkylating agent-induced reversions were enhanced by CdR and decreased by TdR. Finally, 6-amino-2-hydroxypurine induced reversions were enhanced by TdR in mutant I3 and were decreased by TdR or …
Localization of amplified CAD genes on rearranged chromosomes of Chinese hamster cells
Chinese hamster cell lines carrying an amplified CAD region were selected from V79,B7 cells by their resistance to N-phosphonacetyl-L-aspartate (PALA). In one of the selected cell lines, SP PALA (inf1) (supR) L, an acrocentric chromosome with abnormally elongated q arms was identified as a marker for the PALA-resistant phenotype. The marker chromosome carried a homogeneously staining region close to a telomeric nucleolar organizer region. In the same region, localization of amplified CAD sequences was demonstrated by in situ hybridization. The marker chromosome was found to undergo extensive rearrangements. In particular, dicentric chromosomes, occurring with an unusually high incidence, we…