Preferred Label : Telomere Pathway;
NCIt related terms : Telomeres, Telomerase, Cellular Aging, and Immortality;
Alternative definition : BIOCARTA: Telomeres, which define the ends of chromosomes, consist of short, tandemly
repeated DNA sequences loosely conserved in eukaryotes. Telomerase is a ribonucleoprotein
complex which in vitro recognizes a single-stranded G-rich telomere primer and adds
multiple telomeric repeats to its 3-prime end by using an RNA template. Telomerase
may also have a role in de novo formation of telomeres. Telomerase has been identified
in many cultured cell lines and actively dividing cell types. The active reverse transcriptase
component has been identified as the TERT protein. The presence of this factor determines
the availability of the telomerase function. The TERT protein has a high turnover
rate and its expression is regulated by factors that promote growth (c-MYC, v-k-ras,
Bcl-2, and E6) and inhibiting factors (RB and p53) that promote cell death or that
block cell division. It appears that the regulation of active telomerase has many
levels and can be inhibited by TEP1 not releasing TERT or by TRF1 which binds the
end repeats and prevents access to the chromosome ends. Additional modulation is due
to phosphorylation by PKC and AKT or dephosphorylation by PP2A. Human telomeres consist
of many kilobases of (TTAGGG)n together with various associated proteins. Small amounts
of these terminal sequences are lost from the tips of the chromosomes during each
S phase because of incomplete DNA replication, but de novo addition of TTAGGG repeats
by the enzyme telomerase compensates for this loss. Many human cells progressively
lose terminal bases with each cell division, a loss that correlates with the apparent
absence of telomerase in these cells. There has been considerable interest in the
possible relationship between human telomeres and cellular senescence and immortalization.
This interest includes the question of a role in the malignant process and the question
of the use of telomerase inhibitors as anti-tumor drugs. (This definition may be outdated
- see the DesignNote.);
NCIt note : The BIOCARTA Definition (ALT_DEFINITION) for this pathway concept was provided by
BioCarta. This property was not created by, nor is it maintained by the NCI Thesaurus
staff. Additionally, BioCarta is no longer updating its pathway data; thus, the BIOCARTA
Definition might be outdated or inaccurate. Please see the Terms and Conditions for
Use at http://www.biocarta.com/.;
Biocarta ID : h_telPathway;
Origin ID : C39247;
UMLS CUI : C1515261;
Semantic type(s)
- has_gene_product_element
- pathway_has_gene_element
