Human telomerase reverse transcriptase promoter transcriptional machinery (hTERT promoter machinery) (hTERT promoter machinery)

The hTERT promoter-driven transcriptional machinery is the regulatory complex responsible for the expression of the human telomerase reverse transcriptase (hTERT) gene, the catalytic subunit of telomerase (Akincilar et al., 2016, BioEssays). In normal somatic cells, this machinery is silenced, leading to progressive telomere shortening and replicative senescence. However, in approximately 90% of human cancers, the hTERT promoter is reactivated, frequently through highly recurrent point mutations (C228T and C250T) that create de novo binding sites for ETS transcription factors like GABPA (Bell et al., 2015, Science; Huang et al., 2013, Science). This reactivation allows cancer cells to maintain telomere length and achieve cellular immortality. Therapeutically, this machinery is exploited as a cancer-specific switch to drive the expression of oncolytic viruses, such as OBP-301 (Telomelysin), or suicide genes exclusively in malignant cells (Mizuguchi et al., 2021, Molecular Therapy). Additionally, the promoter's G-quadruplex structures and the specific transcription factors recruited to mutated sites represent targets for small-molecule inhibitors aimed at selectively shutting down telomerase expression in tumors (Song et al., 2019, Nature Communications).

Other names

hTERT promoterTelomerase reverse transcriptase promoterTERT promoter-driven machineryhTERT transcriptional apparatusTelomerase promoter complex

The primary mechanism involves utilizing the cancer-specific activity of the hTERT promoter to drive the expression of therapeutic genes, such as viral E1A for oncolytic replication or prodrug-converting enzymes (Mizuguchi et al., 2021). Other mechanisms include the use of small molecules to stabilize G-quadruplex structures within the promoter, which physically obstructs the transcriptional machinery and prevents hTERT synthesis (Song et al., 2019). Additionally, targeting the GABPA transcription factor complex specifically at mutated promoter sites (C228T/C250T) provides a way to inhibit transcription in a mutation-dependent manner (Bell et al., 2015).