Isolation and expression of the reverse transcriptase component of the Canis familiaris telomerase ribonucleoprotein (dogTERT)

The enzyme telomerase plays a crucial role in cellular proliferation and tumorigenesis. Telomerase is an RNA-directed DNA polymerase composed minimally of an RNA subunit (TR) and a catalytic protein component (TERT). The protein component acts as a reverse transcriptase (RT) and catalyses the addition of telomeric repeats onto the ends of chromosomes using the RNA subunit as a template. While both the RNA and catalytic subunits are essential for telomerase activity, the TERT component of telomerase is thought to be the primary determinant for enzyme activity as expression of TERT is largely limited to cells with telomerase activity. We describe here the isolation and sequence characterization of the telomerase catalytic subunit from Canis familiaris (dog), dogTERT. The predicted protein consists of 1123-aa residues and contains all the signature motifs of the TERT family members. Sequence comparisons with previously identified mammalian TERT proteins demonstrate that dogTERT shows the highest level of sequence similarity to the human TERT protein, supporting the dog as a model system for telomerase-based studies. Further, we demonstrate that TERT mRNA expression is associated with telomerase activity in canine-cultured cells, similar to TERT expression in human cells. This data will allow for further investigation of telomerase in canine malignancies as well as the development of the dog as a model system for human telomerase investigations.