Localization of the telomerase RNA in human cells
Telomeres are protective structures at the end of linear chromosomes composed of stretches of TTAGGG repeats. Their gradual shortening is responsible for the induction of senescence, a tumor-suppressor mechanism that causes cells to enter an irreversible cell cycle arrest. While senescence is a highly regulated biological process, tumor cells have the ability to bypass senescence through reactivation of telomerase, a dedicated reverse transcriptase that adds telomeric repeats to the 3’ ends. The telomerase holoenzyme is composed of hTERT, a 120kD catalytic subunit, and hTERC, a complex 451 nt RNA that provides the template for telomere synthesis. Although much is known about the relationship between telomerase and telomeres, a method to detect and visualize the enzyme at telomeres in situ has been elusive. In this study, we will attempt to detect telomerase at the telomeres by fluorescent in situ hybridization (FISH) analysis. Unlike past experiments, this method will focus on increasing the sensitivity of telomerase detection by using multiple probes simultaneously against different regions of hTERC. To this end, 18 FITC-labeled probes against multiple regions of hTERC were synthesized and will be used together for detection in human cells, along with peptide nuclei acid-fluorescent in situ hybridization (PNA-FISH) probes, designed to detect telomeres. Overlap between the fluorescently labeled probe signals for both hTERC and telomeres will represent co-localization of telomerase with the telomere. If successful, this technique will enable future studies on the regulation of telomerase recruitment. Since telomerase deregulation is implicated in cellular immortalization and consequently oncogenic transformation, the results of this study may provide an important tool to further our understanding of cancer biology.
Supported by NIH-RCMI grant numbers MD007599 (formerly RR003037) and NIDA grant R25DA032520.