telomerase

[tĕ-lo´mer-ās]

a DNA polymerase involved in the formation of telomeres and the maintenance of telomere sequences during replication.

tel·o·me·rase

(tel-ō'mĕ-rās),

A reverse transcriptase comprising an RNA template, which acts as a die for the TTAGGG sequence, and a catalytic protein component that is not found in normal, aging somatic cells. Telomerase mediates the repair or preservation of telomere regions (terminal sequences) of chromosomes.

The aging process that takes place in normal somatic cells and the natural limit on the number of times such cells can undergo mitosis involve a sequential shortening of telomeres due to failure of terminal sequences to be replicated during mitosis. Cells in which this shortening does not occur (cancer cells, germ cells, hematopoietic stem cells, and others) display a transient expression of telomerase, which not only delays the erosion of telomeres but actually adds DNA bases to telomeres. Experimental transfection of a gene for the catalytic component of telomerase into normal, aging cells results in extension of telomeres. Restoring telomere length appears to reset gene expression, cell morphology, and the replicative life span. It has therefore been suggested that such procedures may permit therapeutic modification of the cellular mechanisms underlying age-related diseases such as atherosclerosis, osteoarthritis, macular degeneration, and Alzheimer dementia. Cellular aging is but one element of clinical aging, however, others being heredity and environment. Although telomerase expression is an important marker of malignancy, it is not itself the cause of cancer. Telomerase expression and telomere lengthening apparently do not alter normal cell cycle control, chromosome complement, or cell morphology.

Farlex Partner Medical Dictionary © Farlex 2012

telomerase

(tə-lŏm′ə-rās′, -rāz′)

An enzyme that is found in the telomeres of chromosomes in germ cells, stem cells, and most cancer cells and that preserves the length of telomeres across cell divisions.

telomerase

The enzyme that can reforms the TELOMERES at the ends of chromosomes. Telomerase is found in cancers and is able to prevent the shortening that would otherwise occur with repeated replication, thus allowing cancerous cells in culture to achieve immortality. Telomerase consists of two subunits, telomerase reverse transcriptase and an RNA component.

Collins Dictionary of Medicine © Robert M. Youngson 2004, 2005

telomerase

an enzyme that adds specific nucleotides to the ends of eukaryotic chromosomes to form TELOMERES.

Collins Dictionary of Biology, 3rd ed. © W. G. Hale, V. A. Saunders, J. P. Margham 2005

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References in periodicals archive

TERT encodes telomerase reverse transcriptase, and TERC encodes telomerase RNA, which are two major components of telomerase.

A Rare Missense Variant in Telomerase Reverse Transcriptase is Associated with Idiopathic Pulmonary Fibrosis in a Chinese Han Family

3 mL of blood is collected in EDTA vial from both cases and controls for measurement of telomere length and telomerase activity.

COMPARISON OF OXIDATIVE STRESS AND TELOMERE DYSFUNCTION IN HYPERTENSION PATIENTS

But it also increases telomerase activity, which contributes to longevity.

The Secret to Staying Healthier for Longer

In 1985 Blackburn discovered telomerase, and its remarkable capacity to extend a cell's lifespan by essentially rebuilding telomeres with extra bits of DNA, much in the same way that retreading a tyre can make it nearly as good as new.

Enzyme that affects ageing, cancer decoded: study

So the UC Berkeley team isolated telomerase, purified it, and examined it using a state-of-the-art cryoelectron microscope.

Researchers find out enzyme that could help fight aging

Telomerase offsets cellular aging by lengthening the telomeres, adding back lost DNA repeats to add time onto the molecular clock countdown, effectively extending the lifespan of the cell.

Catalytic Cycle Provides Insights Into Immortality Enzyme Telomerase

The trend to increase of TL and telomerase activity with gestational age was also evident from Figure 2, where box-and-whisker plots for two-week periods of gestation are shown.

Dynamics of Telomere Length and Telomerase Activity in the Human Fetal Liver at 5-12 Weeks of Gestation

"We also found that oxidation of the DNA building blocks is a new way to inhibit telomerase activity, which is important because it could potentially be used to treat cancer."

Key mechanisms of inflammation, cancer & aging explored

Keywords: Human telomerase reverse transcriptase, pontin, reptin, dyskerin, telomerase, cancer

Normal and Tumour Tissue mRNA Expressions of Telomerase Complex Genes in Several Types of Cancer

We have previously shown that STAT3 and NF-[kappa]B formed a complex and transcriptionally activated human telomerase reverse transcriptase in breast cancer lines of MDA-MB-231 and MCF7-HER2 [25].

Proinflammatory Cytokines IL-6 and TNF-[alpha] Increased Telomerase Activity through NF-[kappa]B/STAT3 Activation, and Withaferin A Inhibited the Signaling in Colorectal Cancer Cells

(13,14) This has been proven to result from a tocopherol-induced increase in telomerase that persists even into middle-aged cells.

Prevent telomere shortening

However, if this instability continues beyond a certain point, and/or if the P53 system is impaired, or if the cell is exposed to a telomerase activator (such as Tamoxifen), it can cause DNA damage and mutations in both oncogene promotors as well as oncogene suppressors, which can promote the cancer development at the first stages (carcinogenesis).

The role of telomeres in cancer development and progression, and the double edge sword effect with Tamoxifen