Physiological and pathological significance of human telomerase reverse transcriptase splice variants.

Human telomerase reverse transcriptase (hTERT) is tightly regulated at various transcriptional and post-transcriptional levels. Alternative splicing of hTERT has been shown in many human tissues and cell lines regardless of telomerase status and may play a role in regulation of telomerase activity and other cellular functions. Catalytically inactive splice variants make up a substantial proportion of total hTERT mRNA and are at least partly translated into protein. Shifts in splicing patterns occur in development, tumorigenesis and in response to exogenous stimuli in a tissue- and cell type-specific manner. This review focuses on prevalence, patterns and regulation of hTERT alternative splicing, describes associations with telomerase activity and telomere length, and discusses the potential significance of hTERT alternative splice variants in cancer as well as possible telomere-independent functions.