Identification and functional analyses of novel protein interactions and post-translational modifications for the transcription factor deformed epidermal autoregulatory factor-1.

摘要

Deformed Epidermal Autoregulatory Factor-1 (DEAF-1) is a transcription factor that binds TTCG motifs and has roles in fetal development, clinical depression and cancer. In order to further our understanding of the DEAF-1 protein, this study characterizes previously unidentified DEAF-1 interacting proteins and post-translational modifications of DEAF-1. A region encompassing the DNA binding domain of DEAF-1 interacts with the C-terminal Bax interacting domain of the Ku70 subunit of the DNA-PK holoenzyme. Ku70 acts as an anti-apoptotic protein through C-terminal domain and so DEAF-1 was assessed for its ability to influence apoptosis after various stimuli. DEAF-1 acted as a pro-apoptotic protein after intrinsic stimuli. Apoptotic activities occurred through a nuclear, DNA independent mechanism and a mutation that eliminated Ku70 interactions also inhibited DEAF-1 pro-apoptotic activities. Analysis of mammalian purified DEAF-1 indicated a number of phosphorylation sites and also a methylated arginine residue. Various assays were performed on mutated forms of DEAF-1 to determine the significance of the modified sites on DEAF-1 functions and properties. Lysine mutation of the methylated arginine site appeared to augment protein-protein interactions with itself and also Ku70. Alanine mutations at three of the identified phosphorylation sites increased DEAF-1 pro-apoptotic activities. In vitro kinase assays identified CDK5 as potential kinase that can phosphorylate DEAF-1. These studies provide new insight into potential functions, properties, and regulation of DEAF-1.