CDC13P - A SINGLE-STRAND TELOMERIC DNA-BINDING PROTEIN WITH A DUAL ROLE IN YEAST TELOMERE MAINTENANCE

The CDC13 gene has previously been implicated in the maintenance of te lomere integrity in Saccharomyces cerevisiae, With the use of two clas ses of mutations, here it is shown that CDC13 has two discrete roles a t the telomere. The cdc13-2(est) mutation perturbs a function required in vivo for telomerase regulation but not in vitro for enzyme activit y, whereas cdc13-1(ts) defines a separate essential role at the telome re. In vitro, purified Cdc13p binds to single-strand yeast telomeric D NA. Therefore, Cdc13p is a telomere-binding protein required to protec t the telomere and mediate access of telomerase to the chromosomal ter minus.