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Telomerase is a reverse transcriptase enzyme that carries its own RNA molecule (e.g., with the sequence 3′-CCCAAUCCC-5′ in Trypanosoma brucei) [3] which is used as a template when it elongates telomeres. Telomerase is active in gametes and most cancer cells, but is normally absent in most somatic cells.
Here, the single-stranded DNA curls around in a long circle, stabilized by telomere-binding proteins. [26] At the very end of the T-loop, the single-stranded telomere DNA is held onto a region of double-stranded DNA by the telomere strand disrupting the double-helical DNA, and base pairing to one of the two strands.
The two major protein complexes that bind to telomeric DNA in S. cerevisiae are: [citation needed] the Cdc13-Stn1-Ten1 (CST) complex, which binds the single-stranded DNA (ssDNA) of the 3' G-rich overhang at the end of the telomere, and; the Rif1-Rif2-Rap1 complex, which binds the double-stranded DNA (dsDNA) preceding the 3' overhang.
In most multicellular eukaryotic organisms, telomerase is active only in germ cells, some types of stem cells such as embryonic stem cells, and certain white blood cells. [9] Telomerase can be reactivated and telomeres restored to the embryonic state by somatic cell nuclear transfer. [18]
Telomerase is a ribonucleoprotein polymerase that maintains telomere ends by addition of the telomere repeat TTAGGG. The enzyme consists of a protein component with reverse transcriptase activity, encoded by this gene, and an RNA component that serves as a template for the telomere repeat.
A DNA polymerase is a ... The single-strand 3' overhang of the double-strand chromosome with the sequence 5'-TTAGGG-3' recruits telomerase. Telomerase acts like other ...
Telomerase contains a protein subunit that is a reverse transcriptase called telomerase reverse transcriptase or TERT. TERT synthesizes DNA until the end of the template telomerase RNA and then disengages. [93] This process can be repeated as many times as needed with the extension of the 3' end of the parental DNA molecule.
Shelterin (also called telosome) is a protein complex known to protect telomeres in many eukaryotes from DNA repair mechanisms, as well as to regulate telomerase activity. In mammals and other vertebrates, telomeric DNA consists of repeating double-stranded 5'-TTAGGG-3' (G-strand) sequences (2-15 kilobases in humans) along with the 3'-AATCCC-5' (C-strand) complement, ending with a 50-400 ...