Effect of newly identified hTERT-interacting proteins on telomerase activity.

There is a close relationship between telomeres-telomerase and age-related disease. Human telomerase reverse transcriptase (hTERT) is both the catalytic component of human telomerase and the rate-limiting determinant of telomerase activity. Its transcriptional regulation is the primary mode of control of telomerase activity. It is critical to find the proteins interacting with hTERT for exploring the regulatory mechanisms of the hTERT expression and the telomerase activity. In this study, the yeast two-hybrid system was used to screen the potential interactive proteins of hTERT. Six proteins were obtained, among which T-STAR, LOXL3, HKR3, and Par-4 were further confirmed as the interacting proteins of hTERT by co-immunoprecipitation. Then the sense and antisense gene eukaryotic expression vectors containing these four genes were constructed and transfected into tumor cell lines. The correlations among the expression levels of these four proteins, the expression level of hTERT, and the telomerase activity were analyzed. Results showed that the up-regulation of T-STAR expression and down-regulation of HKR3 expression led to the increase of hTERT expression and telomerase activity, while the up- and down-regulation of LOXL3 and Par-4 expressions had no obvious effect. Our results suggested that T-STAR has a positive correlation with the telomerase activity while HKR3 may be a negative regulator. This conclusion is important to further explore the influencing factors or regulation pathways of human telomerase activity, which may be of great importance for the potential clinical application.