High mobility group non-histone chromosomal proteins from chicken erythrocytes

A comparative study of histone deacetylases of plant, fungal and vertebrate cells

The enzymatic equilibrium of reversible core histone acetylation is maintained by two enzyme activities, histone acetyltransferase and histone deacetylase (HD). These enzyme activities exist as multiple enzyme forms. The present report describes methods to extract different HD-forms from three organisms, germinating maize embryos, the myxomycete Physarum polycephalum, and chicken red blood cells; it provides data on the chromatographic separation and partial purification of HD-forms. In germinating maize embryos three HDs (HD1-A, HD1-B, HD2) can be discriminated; HD1-A, HD1-B, and HD2 were characterized in terms of their dependence on pH, temperature and various ions, as well as kinetic parameters (Km for core histones) and inhibition by various compounds. The same parameters were investigated for the corresponding enzymes of Physarum polycephalum, and mature and immature chicken erythrocytes. Based on these results, optimum assay conditions were established for the different enzyme forms. The kinetic data revealed that the maize histone deacetylase HD1-B peak after partial purification by Q-Sepharose chromatography was heterogeneous and consisted of two histone binding sites that differed significantly in their affinity for purified core histones. Optimized affinity chromatography on poly-Lysine Agarose indeed showed that the former defined deacetylase HD1-B can be separated clearly into two individual HD enzyme forms. The high multiplicity of histone deacetylases underlines the importance of these enzymes for the complex regulation of core histone acetylation.

HMG-2 protein in developing rat brain cells

1. The distribution of HMG-2 protein was followed in unfractionated rat brain cells at different stages of development. Its amount gradually decreased and reached the lowest level in the terminally differentiated and non-proliferating cells. 2. In isolated oligodendrocyte nuclei the changes in the content of HMG-2 followed the same pattern of distribution which corresponded to their stage of development and proliferative activity, while in the terminally differentiated and non-proliferating cortical neurons a substantial amount of HMG-2 protein was present up to the twenty-eighth postnatal day. 3. In the presence of anti-HMG-2 antibodies the DNA synthetic activity of oligodendrocyte nuclei in vitro was significantly decreased. The treatment with antibodies affected mainly the DNA replicative activity of the nuclei, while their DNA repair activity remained unchanged.

Tissue-specific pattern of nonhistone high mobility group proteins in various organs of the chicken

Electrophoretic analysis of tissue-specific differences of nonhistone high mobility group (HMG) proteins from nuclei of various organs of the chicken revealed that in organs with a higher proportion of replicating cells (thymus, Bursa Fabricii, spleen) the relative amount of HMG-17 is considerably higher than that of HMG-14; however, in transcriptionally active organs with a very small proportion of replicating cells (glandular stomach, liver) HMG-14 and HMG-17 are present at roughly equal and low amounts. In glandular stomach, liver and spleen, the relative contents of both HMG-1 and HMG-2 are markedly lower than in thymus and Bursa Fabricii. Moreover, the total amount of HMG proteins is higher in those organs which contain replicating lymphocytes.

Protein HMG-17 is hyper-expressed in rat glucagonoma. Single-step isolation and sequencing

High-mobility-group protein 17 (HMG-17) was identified by reversed-phase high-performance liquid chromatography analysis as a major component in acidic extracts of transplantable rat glucagonoma tissue but not in insulinoma tissue of similar origin. The peptide was purified in a single step and the entire sequence of 89 amino acids was determined. Rat HMG-17 has a molecular mass of 9238 Da and shows strong similarity to human, bovine (94.4%) and chicken (88.8%) HMG-17. Six of the seven residues which vary among the mammalian sequences are located within a short segment (positions 64-83) present in the acidic, non-DNA-binding C-terminal part of HMG-17. This region shows least similarity to the otherwise related proteins HMG-14 and H6 (a trout HMG protein). Interestingly, four of the six variable positions are Asp in rat HMG-17 which results in an overall net increase in the negative charge of the C-terminal region. The nature of selective hyper-expression of HMG-17 in glucagon but not in insulin-producing tumor tissue remains to be clarified.

Suitability of staining techniques for the detection and quantitation of nonhistone high mobility group proteins

Three different staining techniques were compared for the detection of nonhistone high mobility group (HMG) proteins after acidic urea-polyacrylamide gel electrophoresis. Silver staining after glutaraldehyde fixation provides the highest detection sensitivity. Because of the acid solubility of HMG proteins special care has to be taken concerning fixation. Staining with colloidal CBB G-250 according to Neuhoff et al. is superior in sensitivity and reliability of quantitation when compared with noncolloidal Coomassie Brilliant Blue R-250. High detection sensitivity and reproducibility of quantitation are prerequisites for studying the tissue-specific expression of HMG proteins. In the present study tissue-specific differences in the molar amounts of various HMG proteins in thymus and erythrocytes of the chicken are documented by application of the methods tested.

Fractionation of plant and animal high mobility group chromosomal proteins by ion-exchange and reversed-phase high-performance liquid chromatography

A method for purifying wheat high mobility group (HMG) chromosomal proteins using a combination of weak cation-exchange and reversed-phase high-performance liquid chromatography (HPLC) is described. Previously reported HPLC systems devised for fractionating HMG proteins of vertebrate animals are not effective for the plant proteins. The system described here can be used for the fractionation of both plant and animal HMG proteins.

Nuclear-envelope vesicles as a model system to study nucleocytoplasmic transport. Specific uptake of nuclear proteins

In the preceding paper [Riedel & Fasold (1987) Biochem. J. 241, 203-212] we have described a procedure for the preparation of nuclear-envelope vesicles (NE vesicles) from rat liver nuclei. These vesicles, which are largely free of components of the nuclear interior, were employed in an assay system in vitro to study protein translocation across the NE. We found that nuclear proteins such as histones, high-mobility-group proteins and acidic chromosomal proteins are specifically taken up and accumulated in the NE vesicles, whereas there is little or no affinity for non-nuclear proteins like immunoglobulin, myoglobin and cytochrome c. The kinetics of histone uptake into the NE vesicles are similar to those obtained for whole rat liver nuclei, and comparative studies with non-vesicular NEs prepared by deoxyribonuclease I-treatment (DNAase-NEs) indicate that the NE of the vesicles affects the uptake kinetics and increases the capacity for nuclear proteins. The uptake of histones into NE vesicles, but not the binding to DNAase-NEs, can be stimulated by GTP and GDP. Furthermore, we found that even very large molecules can be entrapped in the vesicles during their preparation. These results indicate that the NE vesicles might provide a useful system in vitro with which to investigate the structures and mechanisms involved in protein translocation across the NE.

Supercoil-dependent recognition of specific DNA sites by chromosomal protein HMG 2

The ability of the chromosomal high mobility group protein HMG 2 to recognize supercoil-dependent structures within the chicken adult beta-globin gene was investigated by examining its ability to protect such sites from digestion by S1 nuclease. Low molar ratios of HMG 2 were found to be sufficient for complete inhibition of S1 cleavage of a supercoiled plasmid containing the globin gene. Furthermore, HMG 2 protected an S1 cleavage site within the 5'-flanking region of the globin gene, in preference to a palindromic S1 site within the plasmid vector.

Histone H1 and HMG 14/17 are deposited nonrandomly in the nucleus

We have studied the assembly of histone H1 and the high mobility group nonhistones 14/17 by isopycnic analysis after crosslinking density labeled MSB cell nuclei or chromatin. Carbodiimide crosslinking produces dense poly-H1 and hybrid density H1-H2A histone dimers, indicating that new H1 is deposited nonrandomly, albeit nonconservatively relative to new core histones. Core histone-HMG crosslinking with succinimidyl propionate yields dense HMG 14 in uniformly dense particles and new HMG 17 crosslinked to both dense and light protein, implying that HMG 14 and 17 each deposit nonrandomly; but differently with respect to new core octamers. Propionimidate crosslinking yields dense H1-HMG 17 dimers, suggesting that the interactions of new 14/17 with H1 (new HMG 14-old H1, new HMG 17-new H1) are reciprocal to their interactions with the core histones.

Involvement of protein HMG1 in DNA replication

Antibodies against HMG1 inhibit the incorporation of [3H]thymidine in Ehrlich ascites cell nuclei. By the use of specific inhibitors it is shown that HMG1 is needed for the action of the replicative DNA polymerase and not for the reparative one. This is supported by the fact that the addition of exogenous HMG1 to the nuclei enhances the replication process.

Isolation of high-mobility-group proteins HMG1 and HMG2 in non denaturing conditions and comparison of their properties with those of acid-extracted proteins

We describe a method for isolation and purification of the chromosomal proteins HMG1 and HMG2 in non-denaturing conditions which overcomes the difficulties of the published methods concerning yield and purity. The method is based on salt extraction, selective precipitation with ammonium sulfate and DEAE-cellulose chromatography. All studied properties of these proteins (formation of protein tetramers, enhancement of micrococcal nuclease digestion of DNA and chromatin, and protection of 165-basepair DNA in chromatosome) differ significantly from the properties of HMG1 and 2 isolated under denaturing conditions.

High mobility group proteins HMG1 and HMG2 do not decrease the melting temperature of DNA

High mobility group proteins 1 and 2 isolated in non-denaturing conditions cannot decrease the temperature of denaturation of DNA. When they are isolated or treated with tricloroacetic acid a hyperchromic peak below the melting temperature of free DNA appears in agreement with previous data ( Javaherian et al. (1979) Nucl . Acids Res. 6, 3569-3580). We show that this is due to light scattering of aggregated protein at submelting temperatures and not to melting of DNA.

Comparison of the high-mobility-group chromosomal proteins in rainbow-trout (Salmo gairdnerii) liver and testis

Chromatography and characterization of the proteins extracted by 5% (w/v) HClO4 from rainbow-trout (Salmo gairdnerii) liver and testis show that the two tissues present a characteristically different spectrum of high-mobility-group (HMG) proteins. A variant subfraction of HMG C is found in liver, but is not detectable in testis, where even the main fraction of HMG C is present in only very low quantity. A protein, F, which appears to be related to protein H6 has similarly been isolated only from liver and not from testis. Quantification of the HMG proteins in total 5%-HClO4 extracts of trout liver and testis nuclei shows that, in relation to DNA, levels of HMG T1 and T2, and D are more than 2-fold, and C, 20-fold higher in liver than in testis. However, these differences do not result merely from the sequential withdrawal of HMG proteins at the same time that histones are replaced by protamines in the developing spermatid, since in testis, at some stages of maturation, levels of H6 are almost 2-fold higher than in liver. The implications of these findings for the function of HMG proteins are discussed.

Quantitative changes of high mobility group non-histone chromosomal proteins HMG1 and HMG2 during rooster spermatogenesis

The quantitative changes of a group of non-histone chromosomal proteins identified by its solubility, electrophoretic mobility and amino acid analysis as the high mobility group proteins HMG1 and HMG2, were studied throughout rooster spermatogenesis. The ratio HMG1/HMG2 remained constant (0.66 +/- 0.04) during the transition from dividing meiotic and premeiotic cells to nondividing spermatids and from transcriptionally active cells (spermatogonia, spermatocytes and early spermatids) to transcriptionally inactive late spermatids. The ratios HMG1/nucleosomal histone and HMG2/nucleosomal histone increased markedly at the end of spermiogenesis during the transition from nucleohistone to nucleoprotamine when nucleosomes are being disassembled. The high mobility group chromosomal proteins HMG1 and HMG2 were not detectable in the nuclei of rooster spermatozoa.

High mobility group nonhistone chromosomal proteins of the developing sea urchin embryo

The high mobility group or HMG proteins are nonhistone chromosomal proteins that have been found in relatively high amounts in nuclei of many tissues. A number of studies have shown that some of these proteins are preferentially associated with actively transcribed regions of the genome and may play a role in maintaining these regions in an active state. In this study, we undertook an investigation of the high mobility group proteins from the sea urchin, Stronglyocentrotus purpuratus. Initially the putative sea urchin HMGs were extracted from isolated nuclei of hatching blastula-stage embryos with 5% perchloric acid (PCA). The major proteins in this extract were characterized according to their electrophoretic mobility, amino acid composition, and association with isolated deoxyribonucleoprotein particles. The results indicate there is only one "major" sea urchin HMG protein, termed P2 in this paper. An estimate of the amount of P2 in relation to the inner histones, however, was low compared to what has been found for other HMG proteins. Of the other major 5% PCA-extractable proteins, one was identified as the cleavage stage H1. Another protein apparently resulted from H3 contamination in the 5% PCA extract, and the fourth major protein did not have all the characteristics of an HMG. In particular, it was not found associated with nucleosomal particles. The HMG proteins from other developmental stages were then examined. Five percent PCA extracts of nuclei from unfertilized eggs, 2-cell, 16-cell, hatching blastula, gastrula, and pluteus stages were analyzed on SDS- and acetic acid-urea gels. This analysis indicated that P2 exists in two different forms differing slightly in charge. The less basic form was found in the egg, 2-cell and 16-cell extracts. At the hatching blastula stage, both forms were present and by pluteus stage, the more basic form predominated. It appears that P2 is undergoing a developmental change from a less to more basic form. The presence of P2 in the 5% PCA extract of egg nuclei is proof that P2 does not initially appear sometime during embryogenesis but is already in the egg nucleus prior to fertilization.

Conformation of the HMG 14 nucleosome core complex from flow birefringence

Flow birefringence and extinction angles have been measured for HMG 14 complexes with nucleosome core particles from chicken erythrocytes under cooperative "tight" binding conditions, and for the uncomplexed core particles used in the preparations. Results are interpreted using optical models for the observed DNA anisotropy, and are compared to recent small angle neutron scattering results. (19) The studies effectively rule out highly distorted DNA conformations and configurations in which DNA ends are unwound and extended. It is concluded that the most likely conformation of the complex is one in which the DNA superhelix is radially increased, either uniformly or bilaterally, with the DNA ends remaining tightly bound to the particle. This conformation does not require large changes in spatial relationships between the DNA ends compared to the uncomplexed core as would accompany, for example, significant unwinding of the ends. However, it may lead to more subtle but possibly highly significant differences in the angles at which the DNA exits the core particle.

Neutron scattering studies and modeling of high mobility group 14 core nucleosome complex

Considerable evidence relates the nonhistone proteins high mobility group (HMG) 14 and HMG 17 with the structure of active or potentially active chromatin. In this study, bulk nucleosome core particles prepared from chicken erythrocytes and the complex formed by binding two HMG 14 molecules per nucleosome core were studied by use of small-angle neutron scattering techniques. By varying the H2O/2H2O ratio, and hence the contrast between the solvent and the particles, it was possible to determine the radius of gyration of the protein and of the DNA independently and as a function of HMG 14 binding. The results show an increase of 0.9 +/- 0.6 A (mean +/- SEM) in the protein radius of gyration and of 2.7 +/- 0.6 A in the DNA radius of gyration upon binding of HMG 14 to the nucleosome. These changes are considered in the light of several postulated modes for the unfolding or perturbation of the nucleosome structure. Modeling calculations demonstrate that the observed changes in radius of gyration for the DNA and for the protein are too small to be consistent with an overall unfolding or opening of the core particle upon HMG 14 binding. However, the observed changes are consistent with several models that involve only minor changes in the structure. It is postulated that the differences observed may be an indication of the type of conformational change occurring in active nucleosomes.

Theoretical mechanism for synthesis of carcinogen induced embryonic proteins: VIII. Transcriptional theory

In this paper an extension of prior writings on the mechanism by which changes in genic expression is presented. The previous development of these ideas led to a unifying concept of alterations in heterochromatin due to a variety of carcinogenic agents as a pivital process leading to potential re-expressions of genes (1). The following deals just with structural features of chromatin before continuing to finer control levels of gene expression, especially in reference to cancer cells. The DNA methylation status is presented as being an important step in an intermediate stage of chromatin expression along with protein acetylation, phosphorylation and methylation as other means of modifying chromatin status.

Effect of high mobility group nonhistone proteins HMG-20 (ubiquitin) and HMG-17 on histone deacetylase activity assayed in vitro

We have used a method previously described by Reeves and Candido (1) to partially release histone deacetylase from cell nuclei together with putative regulators of the enzyme. Histone deacetylase released from testis cell nuclei and its putative regulators were separated by gel filtration in Sepharose 6B. A peak of low molecular weight contains a heat-stable factor that stimulate histone deacetylase in vitro. Many of the properties of the activator coincide with those of the protein HMG-20 (ubiquitin). Ubiquitin isolated from testis cell nuclei stimulated histone deacetylase in vitro. It has been suggested that HMG-17 partially inhibits histone deacetylase in Fried cell nuclei (2). In our system, HMG-17 shows no inhibitory effect on histone deacetylase activity

Major high mobility group like proteins of Drosophila melanogaster embryonic nuclei

Nuclei from Drosophila melanogaster embryos contain three major proteins which are extracted by 0.35 M NaCl and by 2% perchloric acid. One of these is histone H1, and we refer to the other two as A63 and A13 in accordance with their molecular weights determined by electrophoresis on sodium dodecyl sulfate (NaDodSO4)-polyacrylamide gels (63,000 and 13,000, respectively). The molecular weight of A13, based on its amino acid composition, is approximately 10,000. The amino acid analyses of A63 and A13 show that both of these proteins have high proportions of acidic and basic amino acid residues, a property characteristic of the high mobility group proteins isolated from vertebrate tissues. While A13 comigrates with histone H2A on NaDodSO4-polyacrylamide gels and with H2B on acid/urea gels, it can be readily resolved from the histones by Triton/acid/urea-Na DodSO4 two-dimensional electrophoresis.

Localization of chromosomal protein HMG-1 in polytene chromosomes of Chironomus thummi

The distribution of accessible antigenic sites in the chromosomal protein high mobility group one (HMG-1) in Chironomus thummi polytene chromosomes is visualized by immunofluorescence. The results indicate that (a) HMG-1 is distributed in a distinct banding pattern along the entire length of the chromosomes; (b) the banding pattern obtained with fluorescent antibody does not strictly correspond to that observed by phase-contrast microscopy; and (c) the amount of HMG-1 increases, and the fluorescent banding pattern changes, during the development of the organism. Our findings suggest that the protein may be involved in the modulation of the structure of selected loci in the chromosome.

Selective release of HMG nonhistone proteins during DNase digestion of Tetrahymena chromatin at different stages of the cell cycle

The possible role of LG-1, a Tetrahymena specific HMG protein found in the macronuclear chromatin (Hamana, K. and Iwai, K. (1979) J. Biochem. 86, 789-794), was examined in relation to the chromatin structure. The chromatin isolated from cells synchronized at different stages of the cell cycle contained about one molecule of LG-1 per nucleosome. Limited digestion of the chromatin with DNase I or micrococcal nuclease selectively released LG-1 with the nucleosomal core histones and H1 remained insoluble, bound to the resistant DNA. Depending on the cell stages several types of chromatin structure were distinguished by their nuclease sensitivity. However, the chromatin at different stages exhibited the similar behavior of the LG-1 release with the nucleases as a function of the degree of chromatin solubilization. The results suggest that LG-1 proteins play a role in the chromatin organization which is rather independent of the cell stages.

Salt induced transitions of chromatin core particles studied by tyrosine fluorescence anisotropy

Chromatin core particles containing 146 base pairs of DNA have been found to undergo a single defined transition below 10 mM ionic strength as studied by both sedimentation velocity and tyrosine fluorescence anisotropy. A method is described for the preparation of such core particles from chicken erythrocytes with greater than 50% yield.

The isolation, characterization and partial sequences of the chicken erythrocyte non-histone chromosomal proteins HMG14 and HMG17. Comparison with the homologous calf thymus proteins

Non-histone chromosomal proteins HMG14 and HMG17 were isolated from chicken erythrocyte nuclei. The proteins were characterized by amino acid analysis and by N-terminal sequence analyses. Comparison with the corresponding data for the calf thymus proteins shows that 11% of the residues in HMG14 protein and 5% of the residues in HMG17 protein differ between the two species. Proteins HMG14 and HMG17 therefore do not appear to exhibit the evolutionary stability shown by the nucleosome core histones. Detailed evidence for the amino acid sequence data has been deposited as Supplementary Publication SUP 50101 (4 pages) at the British Library Lending Division, Boston Spa, Wetherby, West Yorkshire LS23 7BQ, U.K., from whom copies may be obtained on the terms given in Biochem. 4. (1978) 169, 5.

Isolation of a high-molecular-weight high-mobility-group-type non-histone protein from hen oviduct

An organ-specific non-histone protein, with a mol.wt. of 95,000, was isolated from hen oviduct. This protein consists of approximately equal amounts of acidic and basic amino acids and has an isolectric point of 7.4. On the basis of its known characteristics, this protein is similar to the high-mobility-group proteins observed in other tissues.