Telomerase reverse transcriptase
Telomerase reverse transcriptase gene is mapped on chromosome 5p15.33 that consists of 16 exons and 15 introns spanning at approximately 35kb. Its promoter is dormant in normal cells but activated in cell immortalization that shows rich in GC yet lacks TATA and CAAT which suggests that expression of this protein may be subject to manifold levels of control and regulated by different factors in diverse cellular contexts. Mutations of telomerase reverse transcriptase gene cause shorter in autosomal congenital aplastic anemia of dyskeratosis congenita-1 wherein leukocytes contains short telomeres and low enzymatic activity.
Telomerase reverse transcriptase plays a significant role in cellular senescence since it is usually repressed in postnatal somatic cells resulting in shortening of telomeres as such, deregulation in somatic cells implicated in oncogenesis. It is also expressed in prenescent fibroblasts, thus disruption of telomerase activity in normal cell slowed cell proliferation and limited cell life span. The physiologic expression of TERT in typical epithelial cells retains proliferative potential and its presence at the earliest stages of tumorigenesis implicated for the regulation of telomerase expression that marked for malignant transformation.
Telomerase reverse transcriptase are present in precise subsets of cells that have long-term proliferative capacity including in mitotically unmoving breast lobular epithelium and regenerating stratum basale of the skin wherein its expression appeared early during tumorigenesis commencing with preinvasive changes in human breast and colon tissues that gradually increase throughout progression within neoplastic lesion.
Gene name: TERT
Protein name: Telomerase reverse transcriptase