Cdc13 Background Information
Telomeres, which are G-rich repetitive sequences at the ends of linear eukaryotic chromosomes, function as protective caps and facilitate chromosome replication. (1-3) During conventional DNA replication, telomeres are not fully replicated at the 5’ end (2,3) Telomerase, the specific DNA polymerase that elongates shortened telomeres, is composed of an RNA subunit and a reverse transcriptase catalytic subunit (2,3). In S. cerevisiae, Est1 (ever shorter telomeres) and Cdc13 bind single-strand telomeric DNA, and both regulate telomere replication (1,3-5). Specifically, Est1 binds to the end of the telomere and mediates telomere recognition by telomerase (1,3,4). In addition to its regulatory function, Cdc13 binds to telomeric DNA to protect the ends from degradation and DNA damage, and to limit transcription of telomeric genes (1,3,5,6). Mutations in the CDC13 and EST1 genes result in cell cycle arrest and senescence, respectively (6,7).
