Telomerase‐dependent Reactivation of Dna Synthesis in Macrophages Implies Alteration of Telomeres

Abstract

In previous work we demonstrated that various types of cultured cells with a limited life span could not reactivate DNA synthesis in the nuclei of mouse peritoneal macrophages in heterokaryons. We now investigate the role of telomerase in the process of the macrophage nucleus reactivation in heterokaryons with immortal telomerase-positive 3T3 Swiss mouse fibroblasts and human fibroblasts with introduced hTERT gene. We report that introduction of the hTERT gene into human diploid fibroblasts results in emergence of telomerase activity in these cells and the ability to induce the reactivation of DNA synthesis in the macrophage nuclei in heterokaryons. Inhibition of telomerase activity in heterokaryons by reverse transcriptase inhibitors (azidothymidine and guanosine polyphosphonate analogues) and by a 2'-O-methyl-RNA oligonucleotide anti-sense to the template region of telomerase RNA, block reactivation of DNA synthesis in macrophage nuclei without inhibiting DNA synthesis in the nuclei of fibroblasts. Our results suggest alterations (shortening or damage) in the macrophage telomere structure. As far as we know, heterokaryons with macrophages are the first cellular model for rapid investigation of the effects of telomerase inhibitors.

Telomerase as a Growth-Promoting Factor

“…29 Cell fusion between macrophages and fibroblasts expressing hTERT induced DNA synthesis in macrophage nuclei in heterokaryons, while fusion with fibroblasts lacking telomerase activity did not. 30 Expression of hTERT in the GM847 cell line did not change the growth characteristics under normal culture conditions; however, it increased the growth rate under growth-limiting conditions 15 (for in-depth discussion of the telomerase-mediated resistance to growth-limiting conditions see ref. 31).…”