Comparing effects of mTR and mTERT deletion on gene expression and DNA damage response: MEF

Telomerase, the essential enzyme that maintains telomere length, contains two core components, TERT and TR. While early studies in yeast and mouse both indicated that loss of telomerase leads to phenotypes that arise after an increased number of generations, due to telomere shortening, recent studies claim additional roles for telomerase components in transcription and the response to DNA damage. To test these telomere length maintenance-independent roles of telomerase components, we examined first generation mTR-/- and mTERT-/- mice with long telomeres. We used gene expression profiling and found no genes that were expressed at significantly different levels when independent mTR-/- G1 mice were compared to mTERT-/- G1 mice and to wild-type mice. In addition, we compared the response to DNA damage in mTR-/-G1 and mTERT-/- G1 mouse embryonic fibroblasts, and found no increase in the response to DNA damage in the absence of either telomerase components compared to wild-type. We conclude that in the wild-type physiological telomere length setting, neither mTR nor mTERT act as a transcription factor or have a role in the DNA damage response. Mouse Embryonic Fibroblasts (MEFs) were generated from age- and sex-matched telomerase wild-type and knock-out C57BL/6J embryos (E12.5-14.5). MEFs were processed for RNA extraction at passage 5. Telomerase null embryos were first-generation (G1) mTERT KO or mTR KO. 3 independent wild-type + knock-out MEF sets were examined. In each set, wild-type + knock-out mice were littermates.