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Biomedical subjects

G Vidali

Publications and source records attributed to G Vidali.

At least 73 records · Page 4Linked to original sources
PubMed1979

Serological analysis of species specificity in the high mobility group chromosomal proteins.

The non-histone chromosomal protein of the high mobility group (HMG-1) present in mouse liver was purified to homogeneity. Antibodies against this protein as well as pure HMG-1 derived from calf thymus and HMG-E purified from duck erythrocytes were elicited in rabbits. The interaction between the antibodies and the immunogens was measured by passive hemoagglutination and by quantitative microcomplement fixation. Quantitative microcomplement fixation assays revealed that the immunological distance between HMG-1 from calf thymus and HMG-1 from mouse liver and duck erythrocytes was 15. This corresponds to 3% sequence differences. It was estimated that amino acid substitution occurred at about seven positions in the polypeptide chain. Thus, HMG-1 proteins display remarkable evolutionary conservation in their primary sequence, similar to that displayed by histones H4 and H3, suggesting that their biological function is dependent on stringent structural requirements. HMG-E protein is significantly different from both HMG-1 and HMG-2 derived from calf thymus. As such, it is a protein unique to avian erythrocytes.

Amino Acid Sequence↗
PubMed1979

Life history of mouse sperm protein. Intratesticular stages.

A basic protein fraction, migrating as a single band in acetic acid-urea gel, distinct from histones, was isolated from mouse sperm collected from vasa deferentia and caudae epididymides and was used to immunize female rabbits. The presence of antibodies to the mouse sperm protein (MSP) in the rabbit antisera was demonstrated by a cytoimmunofluorescence procedure using the cells of origin of the antigenic protein, the mature mouse sperm. The specificity of the antisera was verified by fluid and gel precipitation tests and by crossed immunoelectrophoresis. The latter procedure demonstrated the presence of two antigen-antibody systems, consonant with earlier reports that the basic chromosomal protein of mouse sperm is heterogeneous. MSP antigen in situ was recognized by the specific antibodies of the rabbit antisera only after the smear of mature sperm was treated with either of two reducing agents: 2-mercaptoethanol or dithiothreitol. However, when the immunofluorescence procedure was applied to untreated smears of mouse testicular cells, spermatids of all stages from 1 to 14-15 were positive, while spermatocytes, stage 16 spermatids and spermatozoa were negative. After treatment of testes smears with reducing agent, only spermatocytes remained negative. Those observations indicate the following: (a) MSP is immunogenic in a heterologous species; (b) its antigenic sites are detectable in spermatozoa and spermatids of all stages, but not in primary spermatocytes; (c) those antigenic sites become masked at about stage 15 of spermiogenesis and may be unmasked by treatment with a reducing agent. The interpretation is made, therefore, that one or more components of MSP are assembled at the beginning of spermiogenesis and undergo an alteration in the final intratesticular stage of spermatid maturation. That alteration may be presumed to be the formation of disulfide linkages between the cysteine residues.

Animals↗
PubMed1978

Postsynthetic modification of high mobility group proteins. Evidence that high mobility group proteins are acetylated.

High mobility group proteins were isolated from calf thymus and duck erythrocyte nuclei and the possibility was investigated that these proteins undergo acetylation similar to that occurring in some histones. Dinitrophenylation of the proteins followed by acid hydrolysis and amino acid analysis indicated that 2 to 3% of the lysine residues present were unavailable for reaction with fluorodinitrobenzene. Extensive enzymatic degradation with trypsin and pronase and subsequent amino acid analysis showed a significant amount of material eluting at the position of epsilon-N-acetyllysine. Recovery and acid hydrolysis of this material generated a peak eluting in the lysine position. In vitro radioactive labeling of calf thymus nuclei with [3H]acetate yielded labeled high mobility group proteins. All of these findings are in accord with the conclusion that high mobility group proteins are acetylated and that acetylation occurs as a postsynthetic modification of these proteins.

Acetylation↗
PubMed1978

Suppression of histone deacetylation in vivo and in vitro by sodium butyrate.

In HeLa cells which have been exposed to 5 mM sodium butyrate for 21 h, the level of histone acetylation is greatly increased as compared to control cells (Riggs, M.G., Whittaker, R.G., Neumann, J.R., and Ingram, V.R. (1977) Nature 268, 462-464). Our experiments indicate that the increase in the relative amounts of multiacetylated forms of histones H4 and H3 following butyrate treatment is the result of an inhibition of histone deacetylase activity.

Butyrates↗
PubMed1978

Erythropoiesis in the duck embryo: accumulation of H5 histone during red blood cell maturation.

We have studied the variation in histone composition of the red blood cell during embryonic development of the duck. The problem has been approached by fractionating the cells according to maturity and type in bovine serum albumin density gradients and analyzing electrophoretically histones which have been extracted from purified cell populations. Additional data have been obtained by pulse-labeling experiments and by immunofluorescence techniques. The results indicate that histone H5 may be absent from very immature primitive embryonic red blood cells and that it accumulates in the nucleus during maturation of the cell. A similar relative increase in H5 content is observed during maturation of the definitive erythroid series. Mature adult erythrocytes and mature erythrocytes of the definitive series contain comparable amounts of histone H5 which is present in lower amounts in the mature cells of the primitive cell line.

Animals↗
PubMed1978

Butyrate suppression of histone deacetylation leads to accumulation of multiacetylated forms of histones H3 and H4 and increased DNase I sensitivity of the associated DNA sequences.

Exposure of HeLa cells to Na butyrate leads to an accumulation of multiacetylated forms of histones H3 and H4. Our studies of histone acetylation in HeLa S-3 cells show that 7 mM butyrate suppresses the deacetylation of histones without influencing the rate of radioactive acetate incorporation. An alteration in nucleosome structure in highly acetylated chromatin is indicated by an increased rate of DNA degradation by DNase I. A close association of acetylated histones with the DNase I-sensitive sequences is confirmed by the finding that histones remaining after limited DNase I digestion are depleted in the multiacetylated forms of histones H3 and H4. DNase I treatment has also been found to selectively release [3H]acetyl-labeled H3 and H4 from avian erythrocyte nuclei under conditions previously shown to preferentially degrade the globlin genes in erthyrocyte chromatin. Our results are consistent with the view that histone acetylation provides a key to the mechanism for altering chromatin structure at the nucleosomal level, and that this may explain the selective DNase I sensitivity of transcriptionally active DNA sequences in different cell types.

Acetylation↗
PubMed1977

The location of secondary structure in histone H4.

A total of eight peptides cleaved from calf thymus histone H4 have been studied at several ionic strengths by circular dichroic, infrared and nuclear magnetic resonance spectroscopies to follow the formation of alpha helix, beta structure and self-aggregates. The results are compared with data obtained previously on three other peptides and on the intact molecule in order to define the location of secondary structure in histone H4. It is concluded that there are two alpha-helical sections, the first from residues 55 to 67 and the second of about 12 residues in the region between residues 70 to 90. beta-Structure formation takes place only in the C-terminal part of the intact H4 molecule. Nuclear magnetic resonance studies of the peptides prove that it is the basic N-terminal regions of histone H4 that remain free when the molecule self-aggregates.

Animals↗
PubMed1977

Selective inhibition with sodium cyanate of protein synthesis in colon cancer cells.

Sodium cyanate, which in its tautomeric acidic form, isocyanic acid, acts as a protein carbamylating reagent, has been previously shown to inhibit selectively both DNA and protein synthesis in a variety of solid tumors. We have now compared its effects on protein synthesis in normal colonic epithelium and in colon tumors induced by the administration of 1,2-dimethylhydrazine to rats. The incorporation of 3H-amino acids into cytoplasmic and nuclear protein fractions was suppressed to a much greater extent in the tumor tissue than in colonic epithelial tissue surrounding the tumors of cyanate-treated rats. Despite its effect on tumor protein synthesis in whole animals, cyanate had little or no effect on cultured cells (HT-29) derived from a human adenocarcinoma of the colon, nor on other malignant cell lines such as HeLa S3 cells, chick fibroblasts transformed by the Rous sarcoma virus, mouse Ehrlich ascites tumor cells, or rat Novikoff hepatoma cells. However, the administration of cyanate i.p. does suppress amino acid incorporation by Novikoff hepatoma cells in the peritoneal cavity of rats. The implication that the mechanism of cyanate inhibition of protein synthesis in tumors may require its in vivo metabolism or utilization to produce a postsynthetic modification of circulatory factors is discussed.

Animals↗
PubMed1977

Selective release of chromosomal proteins during limited DNAase 1 digestion of avian erythrocyte chromatin.

Duck erythrocyte chromatin has been treated with DNAase 1 under conditions that are known to digest selectively the structural genes coding for globin mRNAs. This limited digestion releases specific sets of nonhistone chromosomal proteins that are not preferentially released during limited digestion with micrococcal nuclease, which does not selectively attack the globin sequences. Analysis of nucleosome monomer and multimer peaks separated on sucrose gradients after limited digestion with micrococcal nuclease shows that the proteins which are released by DNAase 1 digestion remain associated with the chromatin subunits and can be removed by extraction in 0.5 M NaCl. These proteins are tentatively identified as members of the high mobility group (HMG) proteins (originally described by Goodwin, Sanders and Johns, 1973) in terms of their extractability, electrophoretic characteristics and amino acid composition.

Amino Acids↗