Recruitment of telomerase
Telomerase is a multi-subunit protein-RNA complex. The way in which these subunits are assembled into an active enzyme complex and then transported (“recruited”) to the telomere is complex and not fully understood. We have established in our laboratory two complementary methods to quantitatively detect telomerase at the telomere in live human cells - not an easy task due to its extreme rarity, even in cancer cells. Using our in-house anti-hTERT antibody, we have established a Chromatin ImmunoPrecipitation (ChIP) assay to detect telomerase at the telomere. The second method is a combination of Fluorescence in situ hybridisation (FISH) using a probe complementary to the telomeric DNA and concomitant FISH against hTR; colocalisation of the two probes indicates telomerase at the telomere.
We found that small structures within the cell nucleus called Cajal Bodies are an important stop-over point for telomerase on its way to the telomere. A protein called TCAB1 was known to transport telomerase to Cajal Bodies; we demonstrated that TCAB1 plays an additional role in recruitment by accompanying telomerase all the way to the telomere. We continue to explore a variety of proteins that are involved in recruiting telomerase to the telomere in a cell-cycle dependent manner. Blocking telomere recruitment offers yet another avenue for telomerase inhibition.