Telomerase RNA component

Telomerase RNA component, also known as TERC, is an RNA gene found in is_associated_with::eukaryotes, that is a component of is_associated_with::telomerase used to extend is_associated_with::telomeres. TERC serves as a template for telomere replication (reverse transcription) by telomerase. Telomerase RNAs differ greatly in sequence and structure between vertebrates, ciliates and yeasts, but they share a is_associated_with::5' is_associated_with::pseudoknot structure close to the template sequence. The vertebrate telomerase RNAs have a 3' H/ACA is_associated_with::snoRNA-like domain.

Function
Telomerase is a ribonucleoprotein polymerase that maintains telomere ends by addition of the telomere repeat TTAGGG. This repeat does vary across is_associated_with::eukaryotes (see the table on the telomere article for a complete list). The enzyme consists of a protein component (is_associated_with::TERT) with is_associated_with::reverse transcriptase activity, and an RNA component, encoded by this gene, that serves as a template for the telomere repeat. CCCTAA found near position 50 of the vertebrate TERC sequence acts as the template. Telomerase expression plays a role in cellular is_associated_with::senescence, as it is normally repressed in postnatal is_associated_with::somatic cells resulting in progressive shortening of telomeres. Deregulation of telomerase expression in somatic cells may be involved in is_associated_with::oncogenesis. Studies in mouse suggest that telomerase also participates in chromosomal repair, since de novo synthesis of telomere repeats may occur at double-stranded breaks. Homologs of TERC can also be found in the Gallid herpes viruses.

Clinical significance
Mutations in this gene cause autosomal dominant is_associated_with::dyskeratosis congenita, and may also be associated with some cases of is_associated_with::aplastic anemia.