摘要
本文介绍了^(60)Co-γ辐照对同步的和非同步的CHO细胞的DNA合成和组蛋白合成关系的影响的研究,用~3H-胸腺嘧啶核苷和^(14)C-丙氨酸双标记,未经辐照的和经4Gy～60Gy ^(60)Co-γ辐照的CHO细胞,通过~3H和^(14)C的参入来估价DNA和组蛋白的合成,并用聚丙烯酰胺凝胶电泳鉴定辐照前后组蛋白各组分的变化情况,实验表明: 1)、在4～60Gy剂量范内,无论是同步的还是非同步的CHO细胞其DNA合成和组蛋白合成都受到不同程度的抑制。2)、在辐照后1—3小时,DNA合成和组蛋白合成都受到不同程度的抑制,但辐照后4小时,DNA合成被进一步抑制而组蛋白的合成却逐渐恢复正常,到辐照后48小时组蛋白的合成几乎接近对照水平。3)、16Gy ^(60)Co-γ辐照后8小时,非同步的CHO细胞的DNA合成被抑制的情况比G_1期CHO细胞更为严重。4)、16Gy ^(60)Co-γ辐照S期细胞,在辐照后1—24小时中DNA合成被明显抑制的同时,组蛋白的合成也受到相应的抑制。5)、从未经辐照的和经6、16和60Gy^(60)Co-γ辐照的CHO细胞分别提取全组蛋白,进行聚丙烯酰胺凝胶电泳,从电泳图谱的变化清楚地看到组蛋白H_1和H_3受辐照影响大于组蛋白H_4和H_(2B)+H_(2A),因此我们推测DNA合成和组蛋白H_1和H_3的关系较之组蛋白H_4和H_(2A)+H_(2B)更为密切。
The relationship between histonesynthesis and DNA synthesis in asynchronized and S phase synchronizedCHO cells following γ-irradiation wasinvestigated.Radiation dose was 4——60Gy with dose rate of 0.78 Gy/min.The DNA and histone content ofboth irradiated and unirradiated cellsdoubly labelled with ~3H-thymidine and^(14)C-alanine were determined and thepolyacrylamide gel electrophoresis method was used to display the radiationinduced changes in histone composi-tion.The results have shown: 1) The DNA and histone syn-thesis were inhibited to some extent inboth asynchronized and S phase syn-chronized cells following irradiation,degree of inhibition being increasedwith irradiation dose. 2) The incorporation of ~3H-thy-midine and ^(14)C-alanine into CHOcells was significantly inhibited in thefirst 3 hours after irradiation of 16Gy,from the 4th hour the incorporationrate of ^(14)G-alanine began to recoverand almost backed to normal at the48th hour after irradiation,but theincorporation of ~3H-thymidine wasstill depressed during this period. 3) The rate of DNA synthesis inasynchronous cells was more seriouslydepressed than that in synchronouscells of G_1 stage at the 8th hour afterirradiation. 4) The histone was extractedfrom both irradiated and controlledcells by 0.25 N HCL,and then frac-tionted by polyacrylamide gel elec-trophoresis.It was shown that after irradiation H_1 and H_3 histonebands were markedly deminished.Itis supposed that there may exists certain coupling between DNA synthesis and the synthesis of H_1 and H_2histone.
