Near-Complete Structure and Model of Tel1ATM from Chaetomium thermophilum Reveals a Robust Autoinhibited ATP State

Tel1 (ATM in humans) is a large kinase that resides in the cell in an autoinhibited dimeric state and upon activation orchestrates the cellular response to DNA damage. We report the structure of an endogenous Tel1 dimer from Chaetomium thermophilum. Major parts are at 2.8 Å resolution, including the kinase active site with ATPγS bound, and two different N-terminal solenoid conformations are at 3.4 Å and 3.6 Å, providing a side-chain model for 90% of the Tel1 polypeptide. We show that the N-terminal solenoid has DNA binding activity, but that its movements are not coupled to kinase activation. Although ATPγS and catalytic residues are poised for catalysis, the kinase resides in an autoinhibited state. The PIKK regulatory domain acts as a pseudo-substrate, blocking direct access to the site of catalysis. The structure allows mapping of human cancer mutations and defines mechanisms of autoinhibition at near-atomic resolution. [Display omitted] •3.7-Å structure and near-complete atomic model of autoinhibited Tel1ATM•2.8-Å active site with Mg2+-ATPγS reveals elements of catalysis and autoinhibition•PRD is locked by FATC and blocks active-site access as pseudo-substrate•The N-terminal solenoid has DNA binding activity Jansma et al. use cryoelectron microscopy to determine the structure and provide a near-complete atomic model of the Tel1ATM kinase dimer, showing how this DNA-damage response sentinel is kept in an ATP-bound but autoinhibited state prior to proper activation by DNA breaks.