Differential gene expression of human telomerase-associated protein hTERT and TEP1 in human hematopoietic cells

The maintenance of telomere length is crucial for the survival of cells. Re cently, genes for proteins that consist of human telomerase have been clone d and the results have indicated a close relationship between telomerase ac tivity and its gene expression. We studied the mRNA expression of the telom erase-associated genes, hTERT and TEP1, in hematopoietic cells in order to clarify the relation between them and telomerase activity using semiquantit ative RT-PCR. In polymorphonuclear cells and monocytes isolated from periph eral blood, which had no detectable telomerase activity, no hTERT mRNA expr ession was seen. On the other hand, lymphocytes and CD34-positive cells bot h demonstrated hTERT mRNA expression. TEP1 mRNA was detected in all samples , showing no differential expression. We then assessed hTERT and TEP1 mRNA expression in CD34-positive cells cultured in vitro with growth factors. Af ter 4 weeks of culture, all the cells showed myeloid differentiation and th e telomerase activity was downregulated. hTERT mRNA was expressed in CD34-p ositive cells, but was downregulated in 4-week-cultured cells. TEP1 showed no apparent differential expression. We conclude that hTERT mRNA expression is downregulated in accordance with telomerase downregulation during the c ourse of myeloid differentiation, which suggests that it plays a crucial Po le in the expression of enzyme activity, while TEP1 has a much smaller role to play, if any. (C) 1999 Elsevier Science Ltd. All rights reserved.