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Laboratory of Gene Expression Control


Head T.I.Merkulova, Ph.D.
merkti@niboch.nsc.ru



Distinct nuclear proteins bind to double-strand oligonucleotides comprising the sequences of the most frequent allele of the region between 651 bp and 680 bp of human TDO2 intron 6 and its mutant variants (M1 and M2) and the effect of anti-YY-1 antibodies on mobility shifts of WT and MII oligonucleotides (S _ supershift)





AP1, GME, HNF3 and Ets DNA-binding activities in the nuclear extracts from the livers of mouse strains sensitive or resistant to liver tumor induction. Data set layout: left _ the free probe, middle _ the probe after incubation with the nuclear extract from the livers of control mice, right - mice treated with hepatocarcinogen OAT


Many year studies of the team have focused on two main problems: glucocorticoid regulation of gene expression and the molecular mechanisms of chemical carcinogenesis.

Studies demonstrated that the GREs consist not only of the known conserved consensus sequence, but also of variable flanking sequences that strongly modulate glucocorticoid receptor affinity for the GREs. Based on this idea, a new highly efficient method for searching potential GREs in DNA sequences was developed. Using the method in combination with various experimental approaches, we provided evidence for the existence of the GREs in mouse metallothionein I, rat cytochrome P450e, rat tryptophan 2,3-dioxygenase (TDO2) and the human somatomammotropin genes.

Our data on the presence of the GREs and on the possible existence of the regulatory region of introns 4-6 of the rat TDO2 gene prompted study of the respective region in the human TDO2 gene, a major candidate gene in psychiatric genetics. This study was performed at the Department of Molecular Genetics, Duarte, California. As a result, two single nucleotide substitutions located centrally in intron 6 and associated with a variety of psychiatric disorders, were identified. Using the gel shift technique and specific antibodies, we showed that both mutations cause damage of the YY-1 transcription factor binding site and the appearance of binding sites for the other transcription factors.

Our study on the early steps of hepatocarcinogen action established a clear-cut positive relation between the inhibitory effect of the tested compound on glucocorticoid induction of tyrosineaminotransferase (TAT) in the liver and its subsequent development following exposure to the carcinogen. Members of the HNF3 family were identified as a target for hepatocarcinogen action among transcription factors involved in glucocorticoid regulation of the TAT gene.