Telomeres and telomerase dance to the rhythm of the cell cycle Trends Biology Diagrams In roughly 85% of cancer cells, telomerase is reactivated. This reactivation allows cancer cells to bypass normal aging mechanisms and continue proliferating without limit. The persistence of telomerase activity in tumors is linked to cancer progression, making it an attractive target for therapeutic interventions. Regulation of the Cell Cycle In organisms with linear chromosomes, incomplete replication of telomere ends may lead to the loss of genetic information (1, 2).This so-called end replication problem can be further compounded by telomere attrition and cell cycle arrest as a result of nucleolytic degradation and DNA damage repair reactions ().The telomerase, a ribonucleoprotein with reverse transcriptase activity, synthesizes This study reported, for the first time, the telomere-telomerase dance in single living cells during different phases of the cell cycle (Figure 2a). Gratifyingly, the results obtained with this technology are consistent with previous findings that predicted there are only a few telomere elongation events on a per cell and per S-phase basis [28] .
The TCAB1-hTR association is lost in mitotic cells, suggesting that some elements of the telomerase enzyme are assembled in a cell cycle-regulated manner 136.This observation fits with the Telomerase activity and RNA levels change as cells enter and exit the cell cycle. Gradual telomere shortening in the absence of telomerase does not immediately affect cell cycling; however, "critically" short telomeres are hypothesised to play a role in senescence and the triggering of DNA damage checkpoints.
Regulation of human telomerase in homeostasis and disease Biology Diagrams
Some adult human somatic cells have detectable telomerase activity, Cusanelli E, Ouenzar F, Querido E, et al. Live cell imaging of telomerase RNA dynamics reveals cell cycle-dependent clustering of telomerase at elongating telomeres. Mol Cell. 2011;44:819-27. doi: 10.1016/j.molcel.2011.09.020. [Google Scholar] 110. Bajon E, Laterreur N Cells arrested at the G1/S phase of the cell cycle showed similar levels of telomerase to asynchronous cultures; progression through the S phase was associated with increased telomerase activity. The highest level of telomerase activity was detected in S-phase cells. In contrast, cells arrested at G2/M phase of the cell cycle were almost devoid
In nonactivated CD4+ T cells telomerase activity is detected only in cytoplasm. However, in activated T cells, the TERT protein is present in both, cytoplasm and nucleus. assembly of the telomerase enzyme complex may be regulated during cell cycle. Telomerase assembly could take place during S phase and it is disassembled probably during M
