Effect of TetrahydrocortisolApolipoprotein A-I Complex
on Protein Biosynthesis in Hepatocytes
and on the Secondary Structure of Eukaryotic DNA

L. E. Panin¹*, F. V. Tuzikov², N. A. Tuzikova², A. V. Khar’kovskii¹, and I. F. Usynin¹

¹ Institute of Biochemistry, Siberian Division, Russian Academy of Medical Sciences, Novosibirsk, 630117 Russia;
E-mail: ibch@cyber.ma.nsc.ru
² State Research Center for Virology and Biotechnology “Vector,” Russian Ministry of Health,
Kol’tsovo, Novosibirsk Region, 633159, Russia

Received July 2, 1998

Abstract—The rate of protein biosynthesis in hepatocytes considerably increased in the conditioned medium
of nonparenchymal hepatic cells treated with cortisol, lipopolysaccharides, and high-density lipoproteins. This
effect is due to a biologically active complex between tetrahydrocortisol and apolipoprotein A-I (ApoAI) form-
ing in macrophages having 5- and 5-reductase activity. The tetrahydrocortisol–apolipoprotein A-I complex
enhanced the rate of protein biosynthesis in hepatocytes and had no effect in macrophages and endotheliocytes.
In the absence of tetrahydrocortisol, ApoAI significantly enhanced protein biosynthesis only in macrophages.
Small-angle X-ray scattering has shown that hydrogen bonds between nucleic bases are destroyed and single-
stranded structures are formed upon interaction of tetrahydrocortisol–ApoAI with eukaryotic DNA. Interaction
of the tetrahydrocortisol–ApoAI complexes with DNA is highly cooperative, and at saturation one DNA mol-
ecule binds about 54 molecules of the complex.

Key words: cortisol, tetrahydrocortisol, protein biosynthesis, lipoproteins, apolipoprotein A-I, small-angle
Xray scattering

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