Is telomerase active in gametes?
Telomerase is the enzyme responsible for maintenance of the length of telomeres by addition of guanine-rich repetitive sequences. Telomerase activity is exhibited in gametes and stem and tumor cells. Critically short telomeres cause senescence, following crisis, and cell death.
Is telomerase active in all cells?
Telomerase is an RNA-dependent DNA polymerase, meaning an enzyme that can make DNA using RNA as a template. Telomerase is not usually active in most somatic cells (cells of the body), but it’s active in germ cells (the cells that make sperm and eggs) and some adult stem cells.
What cell types have active telomerase activity?
Telomerase is active in gametes and most cancer cells, but is normally absent from, or at very low levels in, most somatic cells.
Why must telomerase activity take place in germ cells?
Germ cells must transmit genetic information accurately generation after generation. They have a high level of telomerase activity to prevent the loss of genetic information during meiosis. The high level of telomerase helps protect the integrity of the genetic material of the parents.
Why is telomerase not active in somatic cells?
Telomerase activity is absent in most normal human somatic cells because of the lack of expression of TERT; TERC is usually present. On the other hand most mouse cells have telomerase activity (Blasco, 2005). The absence of telomerase activity in most human somatic cells results in telomere shortening during aging.
What is the role of telomerase in cells?
Telomerase is a cellular reverse transcriptase that helps to provide genomic stability in highly proliferative normal, immortal, and tumor cells by maintaining the integrity of the chromosome ends, the telomeres. The activity of telomerase is associated with the majority of malignant human cancers.
Is telomerase expressed in germ cells?
Telomerase is exclusively expressed in highly proliferative cells, including germline cells, granulosa cells, early embryos, stem cells, activated lymphocytes, hematopoietic cells, basal epidermal cells, immortal cells, and certain types of cancer cell populations [33-36].
Do bacteria have telomerase?
Bacteria don’t need telomerase because their chromosomes don’t have telomeres. Most bacterial chromosomes are circular, meaning they have no end.
What happens if telomerase is expressed in somatic cells?
Telomerase is an enzyme that is able to regenerate telomeres. In humans, it is found in some tissues, such as male germ cells, activated lymphocytes, and certain types of stem cell populations. If present in somatic cells, it can turn them cancerous.
Do germ cells have telomerase?
Telomerase is found in fetal tissues, adult germ cells, and also tumor cells. Telomerase activity is regulated during development and has a very low, almost undetectable activity in somatic (body) cells.
Why do germline cells have telomerase?
Telomerase is a ribonucleoprotein that synthesizes telomere repeats onto chromosome ends and is involved in maintaining telomere length in germline tissues and in immortal and cancer cells. Telomerase activity was detected in fetal, newborn, and adult testes and ovaries, but not in mature spermatozoa or oocytes.
What is telomerase activity in gametes?
Telomerase activity is exhibited in gametes and stem and tumor cells. In human somatic cells proliferation potential is strictly limited and senescence follows approximately 50-70 cell divisions. In most tumor cells, on the contrary, replication potential is unlimited.
Is telomerase activity a useful biomarker for cancer diagnosis?
Telomerase activity is readily detected in most cancer biopsies, but not in premalignant lesions or in normal tissue samples with a few exceptions that include germ cells and hemopoietic stem cells. Telomerase activity may, therefore, be a useful biomarker for diagnosis of malignancies and a target for inactivation in chemotherapy or gene therapy.
Is telomerase positive or negative in stem cells?
Telomerase activity has also been assessed in many normal tissue types. Most results showed that normal somatic cells were telomerase-negative, whereas stem cells such as in the germ-line and hemopoietic tissues were telomerase-positive ( 20, 21 ).
How do telomeres contribute to the pathophysiology of cancer?
Telomere attrition during successive cell divisions induces chromosomal instability and contributes significantly to genomic rearrangements that can result in tumorigenesis. Telomeres, repetitive (TTAGGG) DNA–protein complexes at the ends of chromosomes, are crucial for the survival of cancer cells.