Phosphorylation of telomeric repeat binding factor 1 (TRF1) by Akt causes telomere shortening.

Telomeric repeat binding factor 1 (TRF1) belongs to the shelterin complex, which modulates the telomere structures. Akt/protein kinase B activation caused genomic instability and contributes to tumorigenesis, although the molecular mechanism remained little known. Here, we show the direct interaction between Akt and TRF1. In vitro kinase assays showed the phosphorylation of a putative Akt phosphorylation site (Threonine 273) in wild type TRF1, but not the mutant TRF1 (T273A), by Akt. Overexpression of Akt decreased telomere length in a HTC cell line. These results indicate that Akt plays an important role in telomere length regulation, contributing to genomic instability and tumorigenesis.