Figure 2. Cartoon of the TERT gene, protein domains and isoforms.

Chromosomal location, size, 16 exons, 15 introns, and cis-elements of mouse Tert (mTert) and human TERT (hTERT) are shown in panel A. mTert has significantly shorter introns and lacks intronic cis-elements (Alu elements and VNTRs) compared to hTERT. These intronic elements result in human specific regulation of TERT compared to mouse Tert (A). Two major TERT isoforms and four functional protein domains are shown. Only full-length TERT with all 16 exons can be translated into active telomerase enzyme that can synthesize de novo telomere repeats. Stop codon of full-length TERT is in exon 16. In minus beta TERT exons 7 and 8 are spliced out by alternative splicing which induces a frameshifting event and a premature stop codon located in exon 10 (B). Abbreviation: VNTR = variable number tandem repeat, TEN (telomerase N-terminal), TRBD (telomere RNA binding domain), RT (reverse transcriptase), CTE (C-terminal extension). Created with BioRender.com.