Tankyrase, a protein with homology to ankyrins and to the catalytic area of poly(adenosine diphosphate-ribose) polymerase (PARP), is discovered and localized to human telomeres. Tankyrase binds to the telomeric protein TRF1 (telomeric repeat binding aspect-one), a damaging regulator of telomere length routine maintenance. Like ankyrins, tankyrase contains 24 ankyrin repeats in a domain responsible for its interaction with TRF1. Recombinant tankyrase was observed to have PARP exercise in vitro, with both equally TRF1 and tankyrase working as acceptors for adenosine diphosphate (ADP)-ribosylation. ADP-ribosylation of TRF1 diminished its potential to bind to telomeric DNA in vitro, suggesting that telomere purpose in human cells is regulated by poly(ADP-ribosyl)ation. Tankyrase-1 and -2 are intently connected poly(ADP-ribose) polymerases that use an ankyrin-repeat area to bind assorted proteins, such as TRF1, IRAP, and TAB182. TRF1 binding lets tankyrase to regulate telomere dynamics in human cells, while IRAP binding presumably lets tankyrase to regulate the targeting of IRAP.