[Structure and regulation mechanisms of telomerase]

Telomerase is a specialized type of reverse transcriptase which catalyzes the synthesis of telomeric DNA using intrinsic RNA as a template. The enzyme was originally found in a ciliate Tetrahymena, and has been extensively investigated using ciliates or budding yeast. In mammals, the enzyme is highly active in most cancer cells and germ cells, but is inactive in most somatic cells, suggesting the activation of telomerase may be important for the continued cell growth or progression of cancer cells. Recently, two protein components of the mammalian telomerase have been identified using homology to the sequencing data from unicellular eukaryotes. Interestingly, telomerase activity was induced by the expression of catalytic subunit, hTERT, in telomerase-negative normal fibroblast cells, indicating that it plays a key role in the activation of telomerase in cancer cells.