Long non-coding transcripts from telomeres, called telomeric repeat-containing RNA\n(TERRA), were identified as blocking telomerase activity (TA), a telomere maintenance mechanism\n(TMM), in tumors. We expressed recombinant TERRA transcripts in tumor cell lines with TA\nand with alternative lengthening of telomeres (ALT) to study effects on TMM and cell growth.\nAdeno- and lentivirus constructs (AV and LV) were established for transient and stable expression of\napproximately 130 units of telomere hexanucleotide repeats under control of cytomegalovirus (CMV)\nand human RNase P RNA H1 (hH1) promoters with and without polyadenylation, respectively.\nSix human tumor cell lines either using telomerase or ALT were infected and analyzed for TA levels.\nPre-infection cells using telomerase had 1%ââ?¬â??3% of the TERRA expression levels of ALT cells. AV and\nLV expression of recombinant TERRA in telomerase positive cells showed a 1.3ââ?¬â??2.6 fold increase in\nTERRA levels, and a decrease in TA of 25%ââ?¬â??58%. Dominant-negative or small hairpin RNA (shRNA)\nviral expression against human telomerase reverse transcriptase (hTERT) results in senescence, not\ninduced by TERRA expression. Population doubling time, cell viability and TL (telomere length)\nwere not impacted by ectopic TERRA expression. Clonal growth was reduced by TERRA expression\nin TA but not ALT cell lines. ALT cells were not affected by treatments applied. Established cell\nmodels and tools may be used to better understand the role of TERRA in the cell, especially for\ntargeting telomerase.
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