E. R. Isenović, Z. Zakula, G. Koricanac, N. Ribarac-Stepić.
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This investigation addresses the interaction of insulin (INS) and glucocorticoid (GC) ...signaling in the hepatic regulation of tryptophan oxygenase (TO) enzyme activity in the rat. Male Wistar rats (200-250 g b.w) received an injection of the different doses of INS (10, 25, 50, 70 and 100 μg/200 g b.w., i.p.) and were used for experiments 3 h and 18 h after INS administration. This study shows that maximum of TO activity was found at dose of 50 μg of INS with peak increases observed at 3 h and 18 h after injection of INS, while INS had no effect on TO activity in adrenalectomized rats. The analysis of INS effects on glucocorticoid receptor-complex (GC/GR complex) stability shows that complexes from INS-treated rats are less stable than those from control animals. In addition, INS-stimulated stability of glucocorticoid receptor (GR) protein was significantly increased from the controls. Furthermore, the results show that GC/GR complexes from INS-treated rats could be activated and accumulated at higher rate in cell nuclei of control animals. These data support the involvement of INS in modulation of GC signaling pathway which mediates, in part, the activity of TO.
The purpose of this work was to find the character of the dependence between the GC-content of the gene and the level of preterminal codons usage inside it. 84 codon usage tables were used as the ...material (each of them contains average frequencies of codon usage for all encoding districts belonging to one bacterial specie). We also used nucleotide sequences encoding for active centers of bacterial adenylate cyclases. Inverse correlation between the GC-content (G+C) and the total level of preterminal codons usage (PCU) was observed (R = - 0.97). For nucleotide sequences encoding for active centers from adenylate cyclases class I the coefficient of correlation between G+C and PCU is -0.75. For sequences encoding for active centers from adenylate cyclases class III the coefficient of correlation between G+C and PCU is -0.91. Preterminal codons are mostly GC-deficient relative to their synonymous nonpreterminal codons and in absolute terms. The cause of the inverse correlation between G+C and the level of preterminal codons usage is an increase in their frequencies of usage due to mutational AT-pressure and the decrease of their frequencies of usage due to mutational GC-pressure. The evidence of the frequent fixation of nonsense mutations in GC-deficient bacteria was found. The practical conclusion is the following: the higher is the GC-content of gene or genome, the lower is the probability of nonsense mutation inside it.
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