| Abstrakt: |
We have studied telomere length in Schizosaccharomyces pombestrains carrying mutations affecting cell cycle checkpoints, DNA repair, and regulation of the Cdc2 protein kinase. Telomere shortening was found in rad1,rad3, rad17, and rad26mutants. Telomere lengths in previously characterizedrad1mutants paralleled the replication checkpoint proficiency of those mutants. In contrast, rad9,chk1, hus1, and cds1mutants had intact telomeres. No difference in telomere length was seen in mutants affected in the regulation of Cdc2, whereas some of the DNA repair mutants examined had slightly longer telomeres than did the wild type. Overexpression of the rad1+gene caused telomeres to elongate slightly. The kinetics of telomere shortening was monitored by following telomere length after disruption of the rad1+gene; the rate was ∼1 nucleotide per generation. Wild-type telomere length could be restored by reintroduction of the wild-type rad1+gene. Expression of the Saccharomyces cerevisiae RCK1protein kinase gene, which suppresses the radiation and hydroxyurea sensitivity of Sz. pombecheckpoint mutants, was able to attenuate telomere shortening in rad1mutant cells and to increase telomere length in a wild-type background. The functional effects of telomere shortening in rad1mutants were assayed by measuring loss of a linear and a circular minichromosome. A minor increase in loss rate was seen with the linear minichromosome, and an even smaller difference compared with wild-type was detected with the circular plasmid. |
