RUNAWAY TELOMERE ELONGATION CAUSED BY TELOMERASE RNA GENE-MUTATIONS

The ribonucleoprotein enzyme telomerase adds telomeric DNA onto chromo some ends and is normally regulated so that telomeric DNA lengths are kept within defined bounds. In the telomerase RNA gene from the yeast Kluyveromyces lactis, specific mutations that alter telomeric DNA sequ ences result in telomeres elongating to up to 100 times their normal l ength and Impair cell growth. Some mutations cause immediate elongatio n whereas others behave like genetic time bombs, causing elongation on ly after a latent period of hundreds of generations.