RELATIONSHIP BETWEEN EXPRESSION OF C-MYC AND P~(53) GENES AND TERMINAL DIFFERENTIATION DURING INDUCED DIFFERENTION IN FRIEND ERYTHROLEUKEMIA CELLS
Liu Hui-tu Zhang Hong-qing Xue Shao-bai Du Chun-ying You Jin-song Song Ping-gen Wang Xiao-liang Chen Ru-xuan (Dept.of Biology,Beijing Normal University)
We have studied the relationship between expression of c-myc and P53 genes and terminal differentiation (expression of β-globin gene) during induced differentiation by DMSO,DMF,HMBA and inhibition of dif-ferentiation by TPA in Friend erythroleuke-mia cells.Induced MELC differentiation by 5 mM HMBA is associated with an early and rapidly decrease in expression of P~(53) and C-myc genes,levels of the P~(53) and c-myc mRNA markedly decrease within 1 hr and 4 hr.respectively in induced MELC.At the same time the expression of β-globin gene and B~+ % are below detectable level.When cultured with 5mM HMBA at day 2 and day 5 the proportion of Benzidine-reactive cells was increased to 51% and 84.1% respectively.The level of accumulation of β-globin mRNA in the cytoplasm increase markedly and ex-pression of c-myc and P~(53) genes still keeped the very lower levels.By using FCM we demonstrated that the number of the cells contained Gl DNA content increase from 31% to 45% at day 2 and 68% at day 5. Low concentration of TPA inhibited HMBA-induced differentiation of MELC and the inhibition was not caused by cytotoxicity and was reversible.Addition of TPA (10 ng/ ml) decreased proportion of Benzidine-reactive cells to less than 5 % and inhibited expression of β-globin gene.However,the expression of c-myc and P53 genes still remained at very lower level. These experiments suggest that P~(53) and c-myc genes are implicated in MELC prolife-ration.The P~(53) and c-myc genes regulate the cellular proliferation.Even though TPA in-hibited the expression of β-globin gene,rela-ting to differentiation,but didn't affect on expression of P~(53) and c-myc genes.The re-sults demonstrate that the decrease of expres-sion of c-myc and P~(53) genes could not result in expression of β-globin genes directly.So it seems that the effect of two stage and two-set genes was distinguished during inducer-mediated MELC commitment to terminal cell differentiation.