The ex pres sion of Mgmt gene was in ves ti gated by West ern blot anal y sis in the spon ta ne ously im mor tal ized mouse cell line G1 and in its sublines G1-OA and G1-T at dif fer ent pas sages of in vi tro cul ti va tion. The highest level of Mgmt ex pres sion has been re vealed in G1-T subline cells and the low est-in G1-OA subline cells. The in crease in the level of DNA re pair en zyme Mgmt was ob served in the cells of mouse cell line G1 as well as in its subline G1-OA at later pas sages of in vi tro cul ti va tion. Since the G1-OA subline is char ac ter ized by the high est fre quen cies of chro mo somal ab er ra tions, micronucleate and multinucleate cells, it is pos si ble to sup pose a role of de fi ciency of DNA re pair en zyme Mgmt in the in crease of the chro mo somal ab er ra tion level in G1-OA subline.

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Long-term cultivation of cell lines inevitably leads to genetic and epigenetic changes. Aim. A comparative analysis of karyotype and level of the expression of reparative enzyme O 6 -methylguanine-DNA-methyltransferase (MGMT) at different stages of establishment and stabilization of human cell line 4BL and cell line of mouse germ cells G1. Methods. The set of methods was used to research the dynamics of karyotypes changes: the differential staining of chromosomes, FISH-method and comparative genomic hybridization. The level of MGMT expression was analyzed by PCR reaction and Western blot analysis. Results. General trends of establishment of mouse and human cell lines were revealed: at the first stage, which is characterized by increased structural instability of the genome, an increase in the MGMT expression was revealed while at the second stage of stabilization -a decrease in the expression. Therefore, almost complete disappearance of MGMT protein in unmodified form (24 kDa) is observed. Conclusions. Statistically significant correlation between MGMT repair enzyme and mutations induction processes during mammalian cell adaptation and cell line establishment to in vitro was described.

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