Scott L. Weinrich

Detection of telomerase activity in human cells and tumors by a telomeric repeat amplification protocol (TRAP)

The association of human telomerase activity with an indefinite replicative capacity of cells in vitro and advanced tumors in vivo is gaining wide support. The increasing interest in studying various aspects of telomerase expression in cancer required the development of a sensitive and reliable protocol for the extraction and detection of telomerase activity in cell culture material, and from small tissue samples obtained from biopsy, surgical reaction of tumors, and autopsy. Recently a novel procedure for the extraction and detection of telomerase activity was developed (Science 1994; 266: 2011-2015) which resulted in an estimated 10 4 fold improvement in detectability compared with previous methods. The described procedures not only dramatically increased sensitivity but also allowed fast and efficient detec- tion of telomerase activity in a large number of samples. A number of technical aspects which are of critical importance for reproducibility and relia- bility of this assay using clinical material are addressed in this report. In addition, new methods to perform telomerase assays without the use of radioisotopes are described.

Localization of Telomerase hTERT Protein and hTR in Benign Mucosa, Dysplasia, and Squamous Cell Carcinoma of the Cervix

Telomerase has been detected by telomerase repeat amplification protocol (TRAP) assay in cervical dysplasia and squamous cell carcinoma but not in most normal cervical tissues. In the present study, the cellular localization of the protein catalytic subunit of telomerase (hTERT) and the RNA component (hTR) were investigated by a sensitive immunohistochemical technique and by in situ hybridization, respectively. hTERT protein was detected in all diagnostic categories of cervical specimens. hTERT was localized predominantly to the lower suprabasal levels of normal squamous mucosa but was detected throughout virtually all levels of the lesional epithelium in low-grade squamous intraepithelial lesions (LSILs), high-grade squamous intraepithelial lesions (HSILs), and squamous cell carcinoma (SCC). Telomerase expression correlated with hTERT detection in SCC and HSIL but was not detected by TRAP assay in most samples of normal mucosa or LSIL. The distribution of hTR correlated with the localization of hTERT in HSIL and SCC but was restricted to the basal and suprabasal cell layers in normal mucosa and LSIL.

Reconstitution of telomerase activity utilizing human catalytic subunit expressed in insect cells.

Telomerase is a specialized reverse transcriptase responsible for maintaining the termini of linear chromosomes. The human enzyme is a ribonucleoprotein complex minimally comprising a catalytic protein moiety (hTERT) and an RNA subunit (hTR) which acts as the template for the reverse transcriptase reaction. Here we report expression of recombinant hTERT protein in insect cells utilizing a baculovirus expression system. The recombinant hTERT protein reconstitutes telomerase activity in the presence of hTR, either when co-expressed in insect cells or when added in vitro. Reconstitution of telomerase activity using this system will facilitate further analysis of the biochemical and biophysical properties of this enzyme.