Other Regulators of Telomerase

Another protein, TRF1 (TTAGGG repeat binding factor 1), binds to the double-stranded DNA portion of the telomere repeat sequence and regulates the telomere length.

When telomeres are short, there are few TRF1 molecules, and telomerase-mediated telomere lengthening is activated.

When telomeres are long, TRF1 inhibits lengthening. TRF1 probably interacts with POT1 in a complex of proteins (not shown in picture) to promote binding to single-stranded DNA, shielding it from telomerase.

A double helix with green ovals behind it labeled T-R-F-1 which becomes a single strand with blue ovals behind it labeled P-O-T-1.