Objective To study the effects of overexpression of HRAD17 on radiation-induced apoptosis of A549 cells.Methods Transfection of FLAC-tagged HRAD17 expression plasmid into human A549 cells was carried out and flow cytometry was employed tO observe the apoptotic effect.In addition,phosphorylation of p53 Ser46 was detected by Westem blot and the transcription of p53 AIP1 was measured by RT-PCR.Results Overexpression of HRAD17 gene significantly increased radiation-induced apoptosis of A549 cells.Further.Ser46 phosphorylation of P53 protein was increased and transcription of p53 AIP1 gene was elevated in cells overexpressing HRAD17.Conclusions HRAD17 protein can sensitize A549 cells to radiation-induced apoptosis in part by increasing p53 AIP1 expression.

Objective To investigate whether or not adaptive response of the 2BS and A549 cells induced by low dose irradiation.Moreover,to analyze the relationship between the adaptive response and cells cycle regulation. Methods 1.The dose-survival curves of A549 and 2BS cells were figured by colony formation and typan blue cell staining.2.Flow cytometry was used to analyze the cell cycle after the different doses irradiation. Results 1. The adaptive response induced in 2BS cells by low dose,while it was not induced in A549 cells.2.G2 phase arrest of 2BS cells after 75mGy X-ray plus 4Gy 60Co γ-ray irradiation appeared in 30 minutes,and cell cycle recovered in 24 hours. Conclusion The adaptive response of 2BS cell could be induced by low dose irradiation,and there was close relationship between the adaptive responses and the regulation of cell cycle.

Objective To study the effects of overexpression of helicase-like transcription factor (HLTF) on radiation-induced apoptosis of human lung carcinoma cells.Methods Human lung carcinoma cellline A549 were cultured,transfected with FLAG-tagged HLTF expression plasmid pcDNA3.1/HLTF-FLAG (HLTF gene transfection group) ,empty plasmid vector pcDNA3.1 (empty vector group) ,and mock transfection group,respectively,and then exposed to 60Co γ-ray irradiation.Cell apoptosis was observed by flow cytometry 48 h post-irradiation.Western blotting was used to detect the levels of HLTF in the nucleus and cytoplasm and the release of cytochrome C from mitochondria into cytoplasm.Results The apoptosis rate of the HLTF gene group was (32.2 ± 2.1) %,significantly higher than those of the empty vector group [(11.4±2.3)%] and mock transfection group [(11.1 ±1.8)%] (F=101.85,P＜0.05).The level of cytochrome C in the cytoplasm of the HLTF gene group was significantly higher than that of the empty plasmid group.Conclusions HLTF protein sensitizes human lung carcinoma cells to radiation-induced apoptosis,partly by promoting the nuclear-cytoplasma transition of HLTF protein and the increased release of cytochrome C.

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.

AIM　To study the apoptosis and characterizati on of cultured vascular smooth muscle cells (VSMCs) induced by cholestan-3β,5 α,6β-triol(Triol) and compared with 25-hydryoxycholestrol(25-OH). M ETHODS　The culture of vascular muscle smooth cells (VSMCs), light and e lectron transmission microscopy and TdT-mediated dUPT nick-end labeling (TUNEL ) technique. RESULTS　After being treated with oxyterols, VSMCs showed apoptosis of ultrastracture change including shrinkage, condensation of nuclear chromatin, fragmentation nuclei and formation of apoptotic body. TUNEL r evealed that Triol-induced apoptosis in VSMCs was in a concentration-dependent manner. The effect of Triol and 25-OH at a 30 μmol*L-1 concentration i n culture medium induced apoptosis of VSMCs, the former was not but the latter was inhibited by cholesterol at a 50 μmol*L-1 concentration. CO NCLUSION Triol can induce VSMCs apoptosis in vitro and oxysterol-i nduced apoptosis in VSMCs may be mediated through various pathway and different mechanism. Oxysterol-induced apoptosis in VSMCs may play an important role in t riggering atherosclerosis plaque rupture and result to the onset of the acute co ronary syndromes.