A nuclear licence to silence transposons.

Transposon silencing requires the histone methyltransferase SETDB1. In this issue of EMBO Reports, Tsusaka et al [1] and Osumi et al [2] illustrate how the cofactor ATF7IP and its fly homolog Windei (Wde) regulate the methyltransferase function of SETDB1 through its nuclear licensing. The new insight gained from these two articles will shift how we think about epigenetic regulation and its multiple layers of control.