DNA repair protein degradation mediated by helicase-like transcription factor in radiation-induced apoptotic cells

Abstract

Objective To study the effects of helicase-like transcription factor (HLTF)transfection on DNA repair protein level in radiation-induced apoptotic cells.Methods Human lung carcinoma A549 cells were cultured and transfected with FLAG-tagged wild type HLTF (wild type HLTF transfection group),RING structure domain (ubiquitin conjugating region) mutatation HLTF expressing plasmid (mutant transfection group),empty plasmid (congtrol group) respectively.And the other cells were used as mock transfection group.All cells were irradiated with 15 Gy of 60Co γ-rays to induce apoptosis.Western blotting was used to detect the protein levels of the DNA repair proteins HRAD17 and HRAD52 in the transfected cells.Results The levels of HRAD17 and HRAD52 in the wild type HLTF transfection group was significantly lower than that of the control group.There was no significant difference in HRAD17 and HRAD52 levels between the mock transfection group and ubiquity in conjugating region mutation group.complexes of HLTF and HRAD17 and HRAD52 could be found in the irradiation-induced cells.Conclusions HLTF mediates the degradation of HRAD17 and HRAD52 in the irradiation-induced apoptotic cells possibly by the interaction of the protein complex causing ubiquitination of the repair proteins. Key words: Apoptosis; Helicase-like transcription factor (HLTF); RING domain