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.

Mobile Genetic Elements (MGE) make up a large part of the DNA of eukaryotes, in particular, almost 45% of the human genome. Numerous data show the diverse role of these elements in the genome from plasticity factors to mutability or stability. They discuss their role in the evolution of genomes and the evolution of gene regulation. The purpose of this work was to investigate the distribution of MGE in human MGMT gene and their regulatory potential. It has been shown at first that in the human MGMT gene, MGE is present both in the intron sequences and in the promoter region. In the intron sequences, MGEs form composite cluster structures that are the source of various regulatory sequences and have the potential to form alternative promoters. In the promoter region, three sequences of MGE were identified: two LTR repeats and a fragment of the DNA transposon. The MGE fragments in the promoter region of human MGMT also enriched with potential cis-regulatory sequences that may be involved in the regulation of this gene.

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Cytogenetic anal y sis of the spon ta ne ously im mor tal ized mouse cell line G1 has been car ried out on pas sages 15, 24, 53, 68, 104, and 140 of in vi tro cul ti va tion. G1 cells were re vealed to have quan ti ta tive chro mo some changes, dif fer ent chromo somal ab er ra tions, and a par tic u larly high per cent age of Robertsonian translocations. The het er o ge ne ity of cell pop ula tion was ob served to di min ish dur ing long-term cell cul ti va tion. The karyotypic evo lu tion of cells lasted not less than 140 pas sages on the stage of es tab lish ment.