Telomerase RNA component
Encyclopedia
Telomerase RNA component, also known as TERC, is an RNA gene found in eukaryotes, that is a component of telomerase
Telomerase
Telomerase is an enzyme that adds DNA sequence repeats to the 3' end of DNA strands in the telomere regions, which are found at the ends of eukaryotic chromosomes. This region of repeated nucleotide called telomeres contains non-coding DNA material and prevents constant loss of important DNA from...
used to extend telomeres. Telomerase RNAs differ greatly in sequence and structure between vertebrates, ciliates and yeasts, but they share a 5' pseudoknot
Pseudoknot
A pseudoknot is a nucleic acid secondary structure containing at least two stem-loop structures in which half of one stem is intercalated between the two halves of another stem. The pseudoknot was first recognized in the turnip yellow mosaic virus in 1982...
structure close to the template sequence. The vertebrate telomerase RNAs have a 3' H/ACA snoRNA
SnoRNA
Small nucleolar RNAs are a class of small RNA molecules that primarily guide chemical modifications of other RNAs, mainly ribosomal RNAs, transfer RNAs and small nuclear RNAs...
-like domain.
Function
Telomerase is a ribonucleoprotein polymerase that maintains telomere ends by addition of the telomere repeat TTAGGG, this repeat does vary across eukaryoteEukaryote
A eukaryote is an organism whose cells contain complex structures enclosed within membranes. Eukaryotes may more formally be referred to as the taxon Eukarya or Eukaryota. The defining membrane-bound structure that sets eukaryotic cells apart from prokaryotic cells is the nucleus, or nuclear...
s (see the table on the telomere article for a complete list). The enzyme consists of a protein component with reverse transcriptase
Reverse transcriptase
In the fields of molecular biology and biochemistry, a reverse transcriptase, also known as RNA-dependent DNA polymerase, is a DNA polymerase enzyme that transcribes single-stranded RNA into single-stranded DNA. It also helps in the formation of a double helix DNA once the RNA has been reverse...
activity, and an RNA component, encoded by this gene, that serves as a template for the telomere repeat. Telomerase expression plays a role in cellular senescence
Senescence
Senescence or biological aging is the change in the biology of an organism as it ages after its maturity. Such changes range from those affecting its cells and their function to those affecting the whole organism...
, as it is normally repressed in postnatal somatic cell
Somatic cell
A somatic cell is any biological cell forming the body of an organism; that is, in a multicellular organism, any cell other than a gamete, germ cell, gametocyte or undifferentiated stem cell...
s resulting in progressive shortening of telomeres. Deregulation of telomerase expression in somatic cells may be involved in oncogenesis. Studies in mouse suggest that telomerase also participates in chromosomal repair
DNA repair
DNA repair refers to a collection of processes by which a cell identifies and corrects damage to the DNA molecules that encode its genome. In human cells, both normal metabolic activities and environmental factors such as UV light and radiation can cause DNA damage, resulting in as many as 1...
, since de novo synthesis of telomere repeats may occur at double-stranded breaks. Homologs
Homology (biology)
Homology forms the basis of organization for comparative biology. In 1843, Richard Owen defined homology as "the same organ in different animals under every variety of form and function". Organs as different as a bat's wing, a seal's flipper, a cat's paw and a human hand have a common underlying...
of TERC can also be found in the Gallid herpes virus
Herpesviridae
The Herpesviridae are a large family of DNA viruses that cause diseases in animals, including humans. The members of this family are also known as herpesviruses. The family name is derived from the Greek word herpein , referring to the latent, recurring infections typical of this group of viruses...
es.
Clinical significance
Mutations in this gene cause autosomal dominant dyskeratosis congenitaDyskeratosis congenita
Dyskeratosis congenita , also called Zinsser-Cole-Engman syndrome, is a rare progressive congenital disorder which results in what in some ways resembles premature aging...
, and may also be associated with some cases of aplastic anemia
Aplastic anemia
Aplastic anemia is a condition where bone marrow does not produce sufficient new cells to replenish blood cells. The condition, per its name, involves both aplasia and anemia...
.