Fig. 1

Structure of telomere and telomerase complex. A Telomeres are composed of telomeric DNA repeats (5’-TTAGGG-3’)_n and shelterin complex that includes TRF1, TRF2, TIN2, TPP1, POT1, and RAP1 proteins. While TRF1 and TRF2 proteins bind to double-stranded DNA, POT1 protein interacts with single-stranded DNA. The 3’ end of telomere known as G-tail folds back to form T- and D-loop through entering into telomeric DNA duplex. The non-canonical secondary DNA structures defined as G4- and R-loop can also be observed in telomeric structure. B The telomerase complex is basically formed from TERT and TERC subunits. Additionally, the adaptor proteins NHP2, GAR, NOP10, and Dyskerin support structural integrity of this complex. The catalytic subunit TERT contains N- and C-terminal regions and reverse transcriptase motifs between them. These regions harbour subdomains, such as TERT RNA-binding domain (TRBD) at N-terminal region. The TERC subunit includes the conserved region (CR) domains, such as the core domain, CR4/CR5, H/ACA box (CR6/CR8) and CR7. This schematic diagram was created using the BioRender Program (BioRenderCompany; Toronto, Canada)