Flexibility of telomerase in binding the RNA template and DNA telomeric repeat

Significance Telomerase reverse transcriptase (TERT) has a conserved central cavity near the active site. Using enzymatic and mutagenesis analyses, we provide experimental evidence that an artificially looped-out telomeric repeat in the DNA primer can be transiently accommodated in the cavity ofTribolium castaneum (tc TERT). Kinetically,tc TERT requires a minimum of 4 bp between the RNA template and DNA primer for efficient DNA synthesis. An RNA duplex downstream of the RNA-template region after a flexible linker enhances the efficiency of primer extension bytc TERT. In addition to the peripheral cavities that accommodate looped-out RNA during each telomeric repeat synthesis, the central cavity that can accommodate the looped-out DNA may aid RNA-template translocation between cycles of telomeric repeat synthesis.