Cutting edge: Telomerase activation in human T lymphocytes does not require increase in telomerase reverse transcriptase (hTERT) protein but is associated with hTERT phosphorylation and nuclear translocation

Capacity for cellular replication is critically important for lymphocyte fu nction and can be regulated by telomerase-dependent maintenance of telomere length. In contrast to most normal human somatic cells that do not express telomerase due to the failure to transcribe telomerase reverse transcripta se (hTERT), lymphocytes express telomerase in a highly regulated fashion ye t constitutively transcribe hTERT during development and activation. Here, we report that hTERT protein is present in both thymocytes and blood T cell s at equivalent levels despite their substantial differences in telomerase activity, and that induction of telomerase activity in resting CD4(+) T cel ls is not dependent on net hTERT protein increase. Moreover, hTERT is phosp horylated and translocated from cytoplasm to nucleus during CD4(+) T cell a ctivation. Thus, human T lymphocytes regulate telomerase function through n ovel events independent of hTERT protein levels, and hTERT phosphorylation and nuclear translocation may play a role in regulation of telomerase funct ion in lymphocytes.