Researchers identify previously unknown telomere-specific protein.

Telomeres are our own personal inbuilt clock found at the end of chromosomes dictating how and when we age, with these protective caps ensuring no damage comes to the DNA held within.  A person is born with telomeres of a certain length, and every time a cell divides, telomeres get a little bit shorter.  Once the telomere is too short, the cell cannot divide anymore, therefore, researchers are curious whether lengthening telomeres could slow aging, with many studies using a specialized enzyme called telomerase to fine-tune the biological clock.  Now, a study from researchers at The Scripps Research Institute identifies a previously unknown protein that fine-tunes the cellular clock involved in aging.  The team states a novel protein, named TZAP (Telomeric Zinc finger-Associated Protein), binds the ends of chromosomes and determines how long telomeres can be.  The study is published in the journal Science.

Previous studies show understanding telomere length is crucial because telomeres set the lifespan of all cells in the body on an individual basis, dictating critical processes such as aging and the incidence of cancer.  This cellular clock needs to be finely tuned to allow a sufficient amount of cell division to develop differentiated tissues and maintain renewable tissues in the body, and, at the same time, to limit the proliferation of cancerous cells.  For the last few decades, the only proteins known to specifically bind telomeres is the telomerase enzyme and a protein known as the Shelterin complex.  The current study shows TZAP controls a process called telomere trimming, ensuring the telomeres do not become too long.

The current study shows the reduced concentration of the shelterin complex at long telomeres results in TZAP binding and the initiation of telomere trimming.  Results show TZAP binding to long telomeres represents the switch that triggers telomere trimming, setting the upper limit of telomere length, which then allows cells to proliferate.

Data findings show TZAP binds preferentially to long telomeres that have a low concentration of shelterin complex, competing with the telomeric repeat binding factors TRF1 and TRF2.  Results show when localized at telomeres, TZAP triggers telomere trimming, a process resulting in the rapid deletion of telomeric repeats.

The team surmises they have identified a previously unknown specific telomere-associated protein, named TZAP.  For the future, the researchers propose a model for telomere length regulation in mammalian cells based on their new discovery.

Source: The Scripps Research Institute (TSRI) 

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