Autophosphorylation and Self-Activation of DNA-Dependent Protein Kinase.

Aya Kurosawa

doi:10.3390/genes12071091

Abstract

The DNA-dependent protein kinase catalytic subunit (DNA-PKcs), a member of the phosphatidylinositol 3-kinase-related kinase family, phosphorylates serine and threonine residues of substrate proteins in the presence of the Ku complex and double-stranded DNA. Although it has been established that DNA-PKcs is involved in non-homologous end-joining, a DNA double-strand break repair pathway, the mechanisms underlying DNA-PKcs activation are not fully understood. Nevertheless, the findings of numerous in vitro and in vivo studies have indicated that DNA-PKcs contains two autophosphorylation clusters, PQR and ABCDE, as well as several autophosphorylation sites and conformational changes associated with autophosphorylation of DNA-PKcs are important for self-activation. Consistent with these features, an analysis of transgenic mice has shown that the phenotypes of DNA-PKcs autophosphorylation mutations are significantly different from those of DNA-PKcs kinase-dead mutations, thereby indicating the importance of DNA-PKcs autophosphorylation in differentiation and development. Furthermore, there has been notable progress in the high-resolution analysis of the conformation of DNA-PKcs, which has enabled us to gain a visual insight into the steps leading to DNA-PKcs activation. This review summarizes the current progress in the activation of DNA-PKcs, focusing in particular on autophosphorylation of this kinase.

Highlights

Cells regulate the cell cycle and gene expression rapidly in response to both intracellular and extracellular stresses, during which signal transduction is primarily regulated via phosphorylation [1,2,3]
DNA-PKcs has been established as playing a central role in non-homologous end-joining (NHEJ), a DNA double-strand break (DSB) repair pathway, and its activation is dependent on its interactions with the Ku complex [9,10,11]
During NHEJ, the Ku70/Ku80 complex rapidly binds to DNA ends in response to DSBs; DNA-PKcs binds to these DNA ends followed by the recruitment of NHEJ factors such as Artemis and DNA polymerase λ/μ, which subsequently process the DNA ends to generate ligatable ends [11,13]

Summary

Introduction

Cells regulate the cell cycle and gene expression rapidly in response to both intracellular and extracellular stresses, during which signal transduction is primarily regulated via phosphorylation [1,2,3]. Artemis, which is the enzyme responsible for opening the hairpin DNA, has endonuclease activity [11,24] When it forms a complex with DNA-PKcs and undergoes phosphorylation by DNA-PKcs, it acquires structure-specific exonuclease activity [11,24]. There have been a number of higher resolution structural characterizations of DNA-PKcs using X-ray and Cryo-EM analyses [40,41,42,43] Based on this information, in this review, the current understanding of autophosphorylation and the activation of DNA-PKcs has been summarized

Self-Activation of a DNA-Dependent Protein Kinase Catalytic Subunit

Conclusions