[Structure of the interaction sites of eukaryotic DNA with steroid hormone-apolipoprotein A-I complexes].

A high affinity of apolipoprotein A-I for DNA and synthetic oligonucleotides was found using the affinity chromatography, affinity modification, and enzyme analysis. The competitive inhibition and Southern hybridization allowed disclosing the specificity of the interaction of the tetrahydrocortisol-apolipoprotein A-I complex (THC-ApoA-I) with high molecular weight DNA in regions contained GCC/CGG-sequences. The S1 nuclease sensitivity of the duplex CC(GCC)3 x GG(CGG)3 was found to occur under the action of THC-ApoA-I complex. The role of the interaction sites of eukaryotic DNA with steroid (THC, androsterone)-ApoA-I complexes in the initiation of the copy reaction in vitro was revealed.

Tetrahydrocortisol-apolipoprotein A-I complex specifically interacts with eukaryotic DNA and GCC elements of genes.

Tetrahydrocortisol stimulates DNA and protein biosynthesis in hepatocytes only when it enters the complex with apolipoprotein A-I. Tetrahydrocortisol-apolipoprotein A-I (THC-apoA-I) complex specifically interacts with eukaryotic DNA isolated from rat liver. In the process of interaction, rupture of hydrogen bonds between the pairs of nitrous bases occurs with the formation of single-stranded DNA structures. In such state DNA forms complexes with DNA-dependent RNA-polymerase. The most probable site of binding the tetrahydrocortisol-apolipoprotein A-I complex with DNA is the sequence of CC(GCC)(n) type entering the structure of many genes, among them the structure of human apolipoprotein A-I gene. Oligonucleotide of this type has been synthesized. Association constant (K(ass)) of it with tetrahydrocortisol-apolipoprotein A-I complex was shown to be 1.66 x 10(6)M(-1). Substitution of tetrahydrocortisol for cortisol in the complex results in a considerable decrease of K(ass). It was assumed that in the GC-pairs of the given sequence tetrahydrocortisol itself participates in the formation of hydrogen bonds with cytosine, favoring their rupture with complementary base-guanine.

Effect of tetrahydrocortisol-apolipoprotein A-I complex on the secondary structure of eukaryotic DNA and its interaction with RNA-polymerase.

The in vitro effect of tetrahydrocortisol-apolipoprotein A-I complex on native adult rat liver DNA results in the formation of S1 nuclease sensitive fragments that are irregularly distributed throughout a genome. Low-angle X-ray scattering showed that after the interaction with the tetrahydrocortisol-apolipoprotein A-I complex, DNA can bind to RNA-polymerase with a high and dose-dependent cooperativity. This indicates that the effect of tetrahydrocortisol-apolipoprotein A-I complex on secondary eukaryotic DNA structure causes a local denaturation of the double helix, promoting high cooperativity of binding to RNA-polymerase. The reduced form of the hormone, tetrahydrocortisol, previously considered as an inactive metabolite, when complexed with apolipoprotein A-I, promotes a biological function similar to that of a transcription factor.

[Interaction of tetrahydrocortisol-apolipoprotein A-I complex with eukaryotic DNA and with single-stranded oligonucleotides]. / Vzaimodeistvie kompleksa tetragidrokortizol-apolipoprotein A-I c éukarioticheskoi DNK i odnotsepochechnymi oligonukleotidami.

The complex formed by tetrahydrocortisol (THC) and apolipoprotein A-I (ApoAI) specifically interacts with eukaryotic DNA from rat liver. Taken together, physical and chemical data and the results of small-angle X-ray scattering analysis show that interaction of the THC-ApoAI complex with eukaryotic DNA results in deformation of the DNA double helix. Single-stranded fragments were demonstrated to cause deformation of the double helix. In this state DNA forms complexes with DNA-dependent RNA polymerase. This interaction is cooperative and of saturating type; up to six enzyme molecules bind with one DNA molecule. The putative site of complex binding with DNA is the sequence CC(GCC)n found in many genes including the human ApoAI gene. An oligonucleotide of this type was synthesized. Its association constant (Ka) was 1.66 x 10(6) M-1. Substitution of THC with cortysol considerably decreases the Ka. We suggest that THC interacting with GC pairs of the binding site forms hydrogen bonds with cytosine, inducing rupture of the bonds within the complementary nucleic base pair.

[Effect of tetrahydrocortisol-apolipoprotein A-I complex on RNA polymerase interaction with eukaryotic DNA and the rate of protein biosynthesis in hepatocytes]. / Vliianie kompleksa tetragidrokortizol-apolipoprotein A-I na vzaimodeistvie RNK polimerazy s éukarioticheskoi DNK i na skorost' biosinteza belka v gepatotsitakh.

A mechanism of activation of protein biosynthesis in hepatocytes was proposed as effected by the conditioned medium of nonparenchymal liver cells incubated in the presence of high density lypoproteins, cortisol, and lypopolysaccharides. It was found that the increase in the biosynthesis rate was associated with the formation of the tetrahydrocortisol-apolipoprotein A-I (THC-apoA-I) complex in macrophages, which display 5 alpha- and 5 beta-reductase activity and are constituents of nonparenchymal liver hepatocytes. Using the small-angle X-ray scattering technique, it was shown that the THC-apoA-I-eukaryotic DNA interaction may break hydrogen bonds between pairs of complementary nucleic bases and cause the formation of single-stranded DNA fragments capable of binding to DNA-dependent RNA polymerase. The interaction is highly cooperative and has a saturating mode, up to six enzyme molecules being bound per DNA molecule.

[Interaction of eukaryotic DNA with apolipoprotein A-I and its complexes with glucocorticoids]. / Vzaimodeistvie éukarioticheskoi DNK s apolipoproteinom A-I i ego kompleksami s gliukokortikoidami.

A biochemically active complex of apolipoprotein A-I with tetrahydrocortisol was revealed, which increases gene expression in hepatocytes. It was shown by the method of fluorescent probe that titration of rat liver DNA by the apolipoprotein A-I-tetrahydrocortisol complex leads to the appearance of single-stranded fragments. The effect of the complex on the secondary structure of native DNA was confirmed by the method of small-angle X-ray scattering. It was shown that approximately 54 apolipoprotein A-I molecules carrying tetrahydrocortisol as a ligand bind to one molecule of isolated native DNA, inducing a break of hydrogen bonds between the pair of nitrous bases. It is concluded that the cooperative effect of high-density lipoproteins and cortisol in the regulation of gene expression in hepatocytes with the participation of resident liver macrophages is accomplished by a new biochemical mechanism. This mechanism makes itself evident as a result of the interaction of DNA with the apolipoprotein A-I-tetrahydrocortisol complex, the appearance of single-stranded DNA regions in binding sites, and subsequent initiation of gene transcription.

Structural arrangement of the decoding site of Escherichia coli ribosomes as revealed from the data on affinity labelling of ribosomes by analogs of mRNA--derivatives of oligoribonucleotides.

Using derivatives of oligoribonucleotides bearing an active group at the 5'- or 3'-end, the affinity modification of Escherichia coli ribosomes has been investigated in model complexes imitating various steps of initiation and elongation with a different extent of approximation to the real protein-synthesizing system. The protein environment of the ribosome decoding site is determined. The S3, S4, S9, L2, L7/L12 proteins belong to the 5'-region of the decoding site, and the S5, S7, S9, L1, L16 proteins to the 3'-region. In the process of translation the template moves along the external side of the 30 S subunit, from the L1 ridge to the L7/L12 stalk. The structural arrangement of the decoding site or its nearest environment depends on the functional state of ribosomes in the process of translation.

[Preparation of Escherichia coli 70S ribosomes labeled with 35S]. / Poluchenie 70S ribosom Escherichia coli, mechennykh 35S.

[35S]--70S ribosomes (150 Ci/mmol) were isolated from E. coli MRE-600 cells grown on glucose-mineral media in the presence of [35S] ammonium sulfate. The labeled 30S and 50S subunits were obtained from [35S] ribosomes by centrifugation in a sucrose density gradient of 10--30% under dissociating conditions (0.5 mM Mg2+). The activity of [35S]--70S ribosomes obtained by reassociation of the labeled subunits during poly(U)-dependent diphenylalanine synthesis was not less than 70%. The activity of [35S]--70S ribosomes during poly(U)-directed polyphenylalanine synthesis was nearly the same as that of the standard preparation of unlabeled ribosomes. The 23S, 16S and 5S RNAs isolated from labeled ribosomes as total rRNA contained no detectable amounts of their fragments as revealed by polyacrylamide gel electrophoresis. The [35S] ribosomal proteins isolated from labeled ribosomes were analyzed by two-dimensional gel electrophoresis. The [35S] label was found in all proteins, with the exception of L20, L24 and L33 which did not contain methionine or cysteine residues.

[Affinity modification of Escherichia coli ribosomes by 4-[(N-2-chloroethyl)N-methylamino]benzyl-5'-phosphamide hexauridylate in a complex stabilized by codon-anticodon interactions on P and A sites]. / Affinnaia modifikatsiia ribosom Escherichia coli 4-[(N-2-khlorétil)N-metilamino]benzil-5'-fosfamidom geksauridilata v komplekse, stabiliziruemom kodon-antikodonovym vzaimodeistviem v P- i A-uchastke.

Affinity labeling of E. coli ribosomes with 4-[(N-2-chloroethyl)-N-methylamino] benzyl-5'-phosphamide of hexauridylate was studied within the complex containing tRNAPhe at P site and Phe-tRNAPhe at A site directed by EF-Tu and GTP. Ribosomal proteins as well as rRNA both in 30S and 50S subunits were found to be labelled within the complex. Labeled proteins were identified as S3, S9 and L2. Selectivity of affinity labeling with mRNA analogs was shown to depend on the functional state of the ribosomes. Modification was more selective within the complex stabilized by codon-anticodon interaction both at A and P-sites than within the complex in which this interaction takes place preferentially at P site.

[Alkylation of tRNAPhe with 4-(N-2-chloroethyl-N-methylamino) benzyl-5'-phosphamide of d(ATTTTCA)]. / Alkilirovabnie tRNKPhe 4-(N-2-khlorétil-N-metilamino) benzil-5'-fosfamidom d(ATTTTCA).

Alkylation of E. coli tRNAPhe with 4-(N-2-chloroethyl-N-methylamino)benzyl-5'-phosphamide of oligonucleotide d(ATTTTCA) complementary to the sequence UGAAms2i6AA psi in the anticodon loop of tRNAPhe was studied. Three guanine residues--G28/29, G24 and G10 were found to be alkylated. Two binding sites for the reagent in the tRNA were assumed to be present. The efficiency of the alkylation of tRNA from these sites as well as an average association constant (Ka 3,8 X 10(3)M-1) for the reagent interaction with tRNA were evaluated.

Direct cross-linking of heptauridilate to E. coli ribosomes by water-soluble carbodiimide in the complex stabilized by codon-anticodon interaction at both A- and P-sites.

Affinity labelling of E. coli ribosomes is performed by treatment with water-soluble carbodiimide of the complex of ribosomes with (pU)7, tRNAPhe at the P-site and with Phe-tRNAPhe (complex I) and without Phe-tRNAPhe (complex II) at the A-site. The extent of modification is, respectively, 0.06 and 0.026 mol (pU)7 per mol ribosomes. Protein S3 is found as a single labelled protein in complex I, whereas S7, S8, L25 are modified in complex II. Thus, in the absence of a large spacer group within the complex stabilized by codon-anticodon interactions at both A- and P-sites, a highly selective modification occurs.

[Selective alkylation of G24 residue in tRNAPhe]. / Selektivnoe alkilirovanie tRNAPhe po ostatku G24.

Alkylation of E. coli tRNAPhe with 4-(N-2-chloroethyl-N-methylamino) benzyl-5'-phosphamide of oligonucleotide d(pAACCA) was studied. G24 residue located near the sequence C17GGDA21 partially complementary to the oligonucleotide moiety of the reagent was shown to be alkylated. Oligonucleotide d(pAACCA) inhibited the alkylation. Association constant of oligonucleotide derivative with tRNAPhe (10(3) M-1) was evaluated from the dependence of the extent of tRNA modification on the concentration of the reagent. The reported method for selective alkylation of tRNA may be used for preparing photoaffinity derivatives of tRNA bearing an arylazidogroups in desired position.

[Affinity modification of Escherichia coli ribosomes with photoactivated analogs of mRNA]. / Afinnaia modifikatsiia ribosom Escherichia coli fotoaktiviruemymi analogami mRNK.

Oligoribonucleotide derivatives containing the photoactivated arylazidogroup at 5'-end of the oligonucleotide fragment [2-(N-2,4-dinitro-5-azidophenyl) aminoethyl] phosphamides of the oligoribonucleotides, azido-NH (CH2)2NHpN (pN) n-1, were prepared. It was demonstrated that azido-NH(CH2)2NHpA(pA)4 and azido-NH (CH2)2NHpU (pU)3 stimulate the binding of the codonspecific aminoacyl-tRNA with ribosome. After irradiation of the ternary complex ribosome-azido-NH (CH2)2NHpU (pU) n-1 X tRNA with UV-light (lambda greater than 350 nm) covalent binding of the reagent to ribosome occurs. Up to 10% of the reagent, bound in the ternary complex with ribosome, is cross-linked with the ribosomal proteins of 30S and 50S subunits. The ribosomal RNA are not modified by azido-NH (CH2)2NHpU (pU) n-1. The proteins of 30S and 50S subunits, modified with azido-NH (CH2)2NHpU (pU) n-1 with n = 4,7 and 8, were identified. It is shown that proteins of 30S subunits S3, S4, S9, S11, S12, S14, S17, S19, S20 undergo modification. The proteins of 50S subunits L2, L13, L16, L27, L32, L33 are modified. The set of the modified proteins essentially depends on the length of the oligonucleotide part of the reagent and on occupancy of ribosome A-site by a molecule of tRNA.

[Affinity labeling of ribosomes from Escherichia coli with 4-(N-2-chloroethyl-N-methylamino) benzyl-5'-phosphamides of oligouridylates of different length]. / Affinnaia modifikatsiia ribosom Escherichia coli 4-[(N-2-khloretil-N-metil)-amino]-benzil-5'-fosfamidami oligouridilatov raznoi dliny.

4-(N-2-chloroethyl-N-methylamino)benzyl-5'-phosphamides of tetra-, penta-, hexauridilates were used for localization of the proteins organizing the mRNA-binding centre of ribosomes from E. coli. These derivatives, alike oligonucleotides, stimulated the binding of phenylalanyl-tRNA to ribosomes. Within the specific ternary complex these derivatives alkylated both 30S and 50S ribosomal subunits with high efficiency. Tetradecauridylic acid protected ribosomal subunits from alkylation. In the 30S ribosomal subunit these derivatives modified 16S RNA and proteins S3, S4, S9, S11, S13, S14, S19. In the 50S subunit these derivatives alkylated 23S RNA and proteins L7/L12, L13, L23, L25, L32. It was found that oligouridylate derivatives of a different length modified different proteins. The data obtained in this paper indicate that the conformation of the ternary complex "70S.CIRCH2NHpU(pU)n-1.tRNAPhe", where tRNAPhe is bound only to P-site of the ribosome differs from the ternary complex where both A- and P-sites of the ribosome are occupied with tRNAPhe.

[Affinity labeling of the ribosomes from Escherichia coli by 4-(N-2-chloroethyl-N-methyl-aminobenzyl-5'-phosphoamide of heptauridylic acid]. / Affinnaia modifikatsiia ribosom Escherichia coli 4-[(N-2-khlorétil-N-metil)-amino]-benzil-5'-fosfamidom geptauridilovoi kisloty.

4-(N-2-chloroethyl-N-methyl)aminobenzyl-5'-phosphoamide of the heptauridylic acid was used to localize the structures organizing mRNA-binding site of ribosomes from E. coli. Both rRNA and proteins undergo modification in the ribosome 10-18 and 82-90% of the total ribosomal subunit modification, respectively. Using the method of two-dimensional electrophoresis in the acrylamide gel the proteins S5, S11, S13 and L2, L7/L12, L31 which are labelled by the analog of mRNA were identified. We assume these proteins to be located in the vicinity of mRNA-binding centre of ribosomes.

The proteins of the messenger RNA binding site of Escherichia coli ribosomes.

Oligo(U) derivatives with [14C]-4-(N-2-chloroethyl-N-methylamino)benzaldehyde attached to 3'-end cis-diol group via acetal bond, p(Up)n-1UCHRCl as well as with [14C]-4-(N-2-chloroethyl-N-methylamino)benzylamine attached to 5'-phosphate via amide bond, ClRCH2NHpU(pU)6 were used to modify 70S E. coli ribosomes near mRNA binding centre. Within ternary complex with ribosome and tRNAPhe all reagents covalently bind to ribosome the extent of modification being 0.1-0.4 mole/mole 70S. p(Up)n-1UCHRCl alkylates either 30S (n=5,7) or both subunits (n=6,8). rRNA is preferentially modified within 30S subunit. ClRCH2NHpU(pU)6 alkylates both subunits the proteins being mainly modified. The distribution of the label among proteins differ for various reagents. S4, S5, S7, S9, S11, S13, S15, S18 and S21 are found to be alkylated within 30S subunit, proteins L1, L2, L6, L7/L12, L19, L31 and L32 are modified in the 50S subunit. Most proteins modified within 30S subunit are located at the "head" of this subunit and proteins modified within 50S subunit are located at the surface of the contact between this subunit and the "head" of 30S subunit at the model of Stoffler.

[Specific chemical modification of ribosomes in the vicinity of their mRNA-binding center]. / Spetsificheskaia khimicheskaia modifikatsiia ribosom vblizi mRNK-sviazyvaiushchego tsentra

4-N-2-chloroethyl-N-methylamino-benzaldehyde acetal derivatives (RCL-derivatives) of octauridylic and nanauridylic acids were used to localize the structures organizing mRNA-binding site of ribosomes. These derivatives, like free oligonucleotides, stimulate binding of 14C-phenylalanyl-tRNA to ribosomes. They effectively alkylate ribosomes within the specific complex. The extent of 30S subunit alkylations is much greater than that of 50S subunit, alkylation being completely inhibited by preincubation with polyridylic acid, suggesting that the chemical alteration occurs near mRNA-binding site. Both rRNA and proteins undergo modification in 30S subunit (75% and 25% of the total 30S subunit modification, respectively).