Does telomerase repair damaged DNA?
In our model, DNA repair (by homologous recombination or NHEJ) and elongation by telomerase are competing responses at telomeres and at non-telomeric DNA ends. Initially, at both sites, DNA damage proteins sense double-stranded breaks and short telomeres in a similar way and fulfill the same molecular roles.
Is telomerase a repair mechanism?
Although telomeres in different organisms (or even in the same organism under different conditions) are maintained by different mechanisms, the disparate processes have the common goals of repairing defects caused by semiconservative replication through G-rich DNA, countering the shortening caused by incomplete …
What is telomerase repair?
Telomerase enzyme can repair telomere attrition. The enzyme has protein subunit (hTERT) and an RNA subunit. It helps to maintain telomere length by adding telomeric repeats “TTAGGG” to ends of the chromosome during DNA replication.
What is the role of the DNA strand in telomere replenishing?
The ends of the linear chromosomes are known as telomeres: repetitive sequences that code for no particular gene. These telomeres protect the important genes from being deleted as cells divide and as DNA strands shorten during replication. Telomerase adds complementary RNA bases to the 3′ end of the DNA strand.
Does lengthening telomeres increase lifespan?
Telomeres help protect the genetic material inside the DNA. As we age telomeres shorten with each cell division until they cannot divide anymore. The longer the telomere length, the longer the lifespan.
What is the role of telomeres and telomerase?
Telomere shortening can be overcome by telomerase enzyme activity that is undetectable in somatic cells, while being active in germline cells, stem cells, and immune cells. Telomeres are bound by a shelterin complex that regulates telomere lengthening as well as protects them from being identified as DNA damage sites.
Why do telomeres need to be protected from DNA repair?
Telomeres need to be protected from a cell’s DNA repair systems because they have single-stranded overhangs, which “look like” damaged DNA. The overhang at the lagging strand end of the chromosome is due to incomplete end replication (see figure above).
How does a cell reverse the telomere shortening?
Some cells have the ability to reverse telomere shortening by expressing telomerase, an enzyme that extends the telomeres of chromosomes. Telomerase is an RNA-dependent DNA polymerase, meaning an enzyme that can make DNA using RNA as a template.
How are telomeres and telomerase related to aging?
Telomere shortening has been connected to the aging of cells, and the progressive loss of telomeres may explain why cells can only divide a certain number of times. Some cells have the ability to reverse telomere shortening by expressing telomerase, an enzyme that extends the telomeres of chromosomes.
How does the enzyme extend the telomeric repeat?
The enzyme binds to a special RNA molecule that contains a sequence complementary to the telomeric repeat. It extends (adds nucleotides to) the overhanging strand of the telomere DNA using this complementary RNA as a template.