Uncovering the secrets of telomeres, the caps that protect the ends of our chromosomes. An RNA molecule called TERRA helps to ensure that very short (or broken) telomeres get fixed again. The work of researchers at the Institute of Molecular Biology (IMB) and Johannes Gutenberg University Mainz (JGU) provides new insights into cellular processes that regulate cell senescence and survival in aging and cancer.
In their recent paper, published in the journal Cell, Luke and his group have shown that one of the keys to understanding this problem is TERRA. TERRA is an RNA species that accumulates specifically at the ends of critically short telomeres by binding directly to the DNA and signals to the cell that these telomeres should be repaired, allowing the cell to carry on dividing.
TERRA actually accumulates at all telomeres, but at long telomeres it is rapidly removed with the help of proteins Rat1 and RNase H2. These proteins bind preferentially to the long telomeres and ensure that TERRA is removed, but they are not present at the critically short telomeres, which means that TERRA remains for a longer time. This mechanism ensures the subsequent repair of the short telomere, which is crucial for the cell to survive and keep dividing.
Luke’s work was carried out in yeast; however, telomeres and TERRA are found across all organisms with linear chromosomes.