Individual histone messenger RNAs: Identification by template activity

Newly synthesized polysomal messenger RNAs from cleavage stage embryos of the sea urchin Arbacia punctulata and Lytechinus pictus that contain putative histone mRNAs have been fractionated on 6% polyacrylamide slab gels. At least 8 RNA species with unique electrophoretic mobilities have been recognized. The complex of RNAs has been eluted from the gels in three groups, A, B, and C, in increasing order of mobility. The template activity of the three fractions and the unfractionated starting material was examined in the mouse Krebs II ascites tumor cell-free protein synthesizing system. The unfractionated messenger complex programs the synthesis of proteins that coelectrophorese exclusively with sea urchin histones in both sodium dodecyl sulfate and acid urea gel systems. The products of in vitro protein synthesis stimulated by the individual polyacrylamide gel RNA fractions were similarly examined. Each stimulated protein synthesis and was enriched for specific histone templates. We conclude that RNA fraction A is template for histone f1, C is template for histone f2a1, and B serves as template for f2b, f2a2, and f3 histones. A minor degree of contamination of the A and B RNA fractions was obvious from the production of other histones by each template. The co-electrophoresis of specific template activity with specific radiolabeled RNAs supports the concept that most or all of the labeled RNAs are indeed themselves the histone mRNAs.     

Histone messenger RNAs of the mouse testis

A 6-12S RNA fraction has been isolated following sucrose gradient fractionation of mouse testis RNA, and further resolved into poly A+ and poly A- RNA fractions by oligo-(dt)-cellulose chromatography. Polyacrylamide gel electrophoresis of products formed in a reticulocyte lysate-dependent cell-free translation system has enabled identification of histone variants, H1t, H2S, H2A . X, an H4-like protein and a low Mr protein (presumably TP and/or protamine). Cell-free synthesis of a number of these histone variants appears to be directed by poly A+ mRNAs.     

Chromosomal proteins of Drosophila melanogaster and an approach for their localisation on polytene chromosomes

Chromosomal proteins have been prepared from embryos of Drosophila melanogaster and separated into histone and nonhistone fractions by a procedure which completely avoids exposure to extremes of pH. These fractions have been characterised by amino acid analysis and gel electrophoresis. Antisera have been prepared against whole chromatin and against the two chromosomal protein fractions. — A new method is described for the preparation of Drosophila salivary chromosomes. This method employs microdissection techniques and completely avoids the use of acid fixatives. Preservation of fine structure in these preparations is comparable to, if not better than, that in classical acid-fixed preparations. Antisera against embryo chromatin and chromosomal protein fractions react with the salivary chromosome preparations. These reactions exhibit selectivity with different chromosomal structures. Evidence is presented suggesting a specific distribution of protein antigens along the chromosome.     

Isolation, identification, and characterization of histones from plasmodia of the true slime mold Physarum polycephalum using extraction with guanidine hydrochloride

Histones from plasmodia of the true slime mold Physarum polycephalum have been prepared free of slime by an approach to histone isolation that uses extraction of nuclei with 40% guanidine hydrochloride and chromatography of the extract on Bio-Rex 70. This procedure followed by chromatography or electrophoresis has been used to obtain pure fractions of histones from Physarum microplasmodia. Physarum microplasmodia have five major histone fractions, and we show by amino acid analysis, apparent molecular weight on three gel systems containing sodium dodecyl sulfate, mobility on gels containing Triton X-100, and other characterizations that these fractions are analogous to mammalian histones H1, H2A, H2B, H3, and H4. Significant differences between Physarum and mammalian histones are noted, with histone H1 showing by far the greatest variation. Histones H1 and H4 from Physarum microplasmodia have similar, but not identical, products of partial chymotryptic digestion compared with those of calf thymus histones H1 and H4. Labeling experiments, in vivo, showed that histone H1 is the major phosphorylated histone and approximately 15 separate phosphopeptides are present in a tryptic digest of Physarum histone H1. The core histones from Physarum, histones H2A, H2B, H3, and H4, are rapidly acetylated; histone H4 shows five subfractions, analogous to the five subfractions of mammalian histone H4 (containing zero to four acetyllysine residues per molecule); histone H3 has a more complex pattern that we interpret as zero to four acetyllysine residues on each of two sequence variants of histone H3; histones H2A and H2B show less heterogeneity. Overall, the data show that Physarum microplasmodia have a set of histones that is closely analogous to mammalian histones.     

Histones from Trypanosoma lewisi nuclei]

A preparation of total histones has been isolated for the first time from the purified fractions of T. lewisi cell nuclei and characterized in terms of its chemical composition and RNA-polymerase activity. A special attention during the isolation procedure was given to the repression of proteolytic degradation of the histones. The amount of protein in the chromatin is equivalent to that of DNA. The amino acid composition and heterogeneity of the protein during polyacrylamide gel electrophoresis in an acid system and in the presence of sodium dodecyl sulfate are typical for histones. Using two-dimensional electrophoresis, differential staining of electrophoregrams and ion-exchange chromatography on CM-cellulose the total preparation has been found to be made up of five fractions: two -- arginine-rich (one of them identical to histone H4, the other being similar to histone H3 from calf thymus); two -- moderately lysine-rich fractions, slightly differing in their properties from histones H2A and H2B from calf thymus, and one specific fraction with mol. weight of 16 000 and an extremely high positive charge. The above methods in combination with specific extraction have been used to demonstrate the absence of a typical lysine histone in the preparation, which is correlated with the absence of typical methaphase chromosomes during mitosis in T. lewisi.     

Countercurrent-distribution studies on histones

1. The possibilities of fractionating histones and histone fractions by means of countercurrent distribution between two phases formed by water and butan-2-ol, in the presence of various concentrations of trichloroacetic acid, have been examined. 2. Although the principal histone fractions differ considerably in their partition ratios, a satisfactory resolution of the principal histone fractions from the whole histone has not been achieved. 3. The histone fractions obtained by other methods can be resolved with suitable concentrations of trichloroacetic acid. Besides the main peak several subsidiary peaks are obtained in most cases, the composition of which corresponds with others of the main fractions. 4. The method is therefore capable of removing from the principal fractions as previously prepared contamination by other fractions. 5. Except in one case, no fraction with composition unlike other fractions has been obtained. In several cases the material isolated from the principal peak behaves as a single component on running again. In two cases fractions with similar compositions were distinguished by countercurrent distribution.     

Histone variants and histone modifications in chromatin fractions from heterochromatin-rich Peromyscus cells

In order to investigate the relationship between condensed heterochromatin and histone modification by acetylation, phosphorylation and amino acid variation, chromatin from cultured Peromyscus eremicus cells, containing 35% constitutive heterochromatin, was fractionated into heterochromatin-enriched and heterochromatin-depleted fractions. The constitutive heterochromatin content of these fractions was determined from satellite DNA content. The distribution of phosphorylated and acetylated histones and amino acid variants of histone H2A in these chromatin fractions was examined by gel electrophoresis. Fractionation of histones demonstrated that endogenous histone phosphatase activity was high in chromatin fractions and could not be inhibited sufficiently to allow accurate histone phosphorylation measurements. However, sodium butyrate did inhibit deacetylation activity in the fractions, allowing histone acetylation measurements to be made. It was found that the constitutive heterochromatin content of these fractions was proportional to both their unacetylated H4 content and their more-hydrophobic H2A content. These observations support, by direct measurement, earlier experiments (Exp cell res 111 (1978) 373; 125 (1980) 377; 132 (1981) 201) suggesting that constitutive heterochromatin is enriched in unacetylated arginine-rich histones, and in the more hydrophobic variant of histone H2A.     

The isolation of nuclei and basic nucleoproteins from the cellular slime mold Dictyostelium discoideum.

A method is described for the isolation of nuclei from an axenic strain of Dictyostelium discoideum using a sorbitol/Ficoll solution and low concentration of Triton X-100. Basic proteins have been extracted from the nuclei and on polyacrylamide gel electrophoresis yield a consistent pattern in which five major groups or bands predominate. Four of these five fractions comigrate with calf thymus histones and one fraction seems to be unique to D. discoideum. The slowest moving of the five fractions is soluble in 0.5 M perchloric acid and comigrates with calf thymus histone F1. After recovery from the perchloric acid solution by precipitation with acetone this fraction yielded one major band on electrophoresis.     

Separation and quantitative analysis of rat testis histones by one-dimensional gel electrophoresis

A procedure is presented for direct separation and quantitative analysis of histones of rat testis by use of one-dimensional cylindrical gel electrophoresis in acid/urea/polyacrylamide gels at two concentrations of urea. After separation and staining with amido black the histone fractions are determined by extraction of bound dye and spectrophotometric analysis. This method provides a rapid and accurate procedure for determination of microgram amounts of the histone subfractions which are unique to the testis as well as those which are found in somatic cells, and it is particularly useful for determination of molar proportions of the histones.     

Studies on the histones of the ciliate Stylonychia mytilus

Histones were extracted from pure macronuclei and maoronuolear anlagen and were analyzed by different electrophoretic techniques and by amino acid analysis. Fractionation of the histones on SDS-gels showed that the histone fractions of the macronucleus and the macronuclear anlagen are identical in their molecular weights. Comparison with calf thymus histone fractions showed considerable similarities in the molecular weights. Analysis by polyacrylamide-urea gel electrophoresis and by amino acid analysis showed quantitative differences in some histone fractions between these two types of nuclei.     

Isolation of the Chromocenter Fraction from Mouse Liver Nuclei

A new method for isolation of the constitutive heterochromatin (chromocenters) from interphase nuclei of mouse liver has been developed. This method allows separation of chromocenters of different size. Chromocenter fractions are essentially free of nucleoli and other contaminants. In contrast to nuclei and nucleoli, the chromocenter fraction is characterized by simpler protein composition, this fraction having a reduced number of proteins (especially high molecular weight proteins). Chromocenters contain all histone fractions; however, the relative proportion of histone H1 is lower and histone H3 is higher than in the total nuclear chromatin. The amount of non-histone proteins of 51, 63, 73, and 180 kD is higher in the chromocenter fraction than in nuclei and nucleoli. The use of immunocytochemistry and immunoblotting methods revealed the presence of the specific kinetochore component, CENP A protein. This suggests tight association of some molecular kinetochore components with chromocenters in the interphase.     

Changes in nuclear proteins of rat testis cells separated by velocity sedimentation.

The technique of velocity sedimentation at unit gravity has been used to separate rat testis cell suspensions into fractions enriched in particular cell types. Changes in the nuclear proteins from the various fractions have been characterized by polyacrylamide gel electrophoresis, and correlated with the changing morphology of the nucleus during spermatogenesis. The most striking alterations in both protein composition and nuclear morphology occur during spermatid maturation as both histone and non-histone proteins are replaced by highly basic, low molecular weight, spermatidal proteins. This replacement process is accompanied by a quantitative reduction in both histone and non-histone proteins. The synthesis of at least three basic proteins has been identified with late stage spermatids. One of these proteins is a highly basic sperm-specific protein containing high levels of cyst(e)ine and arginine. A second protein synthesized in late stage spermatids is lysine rich, while the third protein contains cyst(e)ine and co-migrates with histone F2a1 on acid-urea polyacrylamide gels. The changes in protein composition of rat testis nuclei after irradiation or hypophysectomy reflect the resulting changes in the cellular composition of the testis. After selective elimination of the germinal cells by irradiation, the electrophoretic pattern of acid-soluble proteins from the testis is very similar to that of somatic tissue. Thus, the cellular specificity of nuclear proteins demonstrated here using cell separation techniques is also apparent following treatments which selectively alter the cellular composition of the testis.     

The histone H5 variant in Xenopus laevis

The presumptive histone H5 of Xenopus laevis has been characterized by SDS and acid-urea-Triton polyacrylamide gel electrophoresis and compared with chicken histone H5. Chicken H5 has a lower electrophoretic mobility compared to that of Xenopus H5 in both gel systems. It is shown, using a polyclonal antiserum against chicken H5, that the Xenopus histone H5 is immunologically related to chicken histone H5. Monoclonal antibodies have been prepared to the Xenopus histone types H5 and H1A, that do not cross-react, as determined by their reactivity in an enzyme linked immunosorbent assay and by their ability to react with either H1A or H5 in an immunochemical test on total erythrocyte histones that are transferred to nitrocellulose after fractionation by SDS- or acid-urea polyacrylamide gel electrophoresis. As all nuclei of erythrocytes from adult Xenopus laevis can be shown to contain histone H1A and H5, these monoclonal antibodies can be used to further delineate the role of H5 in tissue differentiation.     

Chromatographic fractionation of histones on Bio-Gel P.

Chromatography of histones on columns of polyacrylamide beads (Bio-Gel P) was studied to determine what factors influence separations. The fractionation achieved on eluting with dilute HCl depends on the HCl concentration, the temperature, and a variable characteristic of the gel which is independent of its pore size and mesh. Somatic histone will be eluted in three, four, or five separate fractions, depending on these variables. Retardations of histones that apparently result from interactions between their charged groups and those of the gel have a strong influence on resolution between different types. Certain histones are retarded more than others when the HCl concentration or temperature is lowered or if the gel has been hydrolyzed. Increases in retardation lead to resolution of more fractions; but if too extreme, coelution of the most retarded fractions will occur.     

Structural organization of human simian virus 40 chromosomes. I. Heterogeneity and composition of nuclear DNA-protein complexes at different stages of lytic infection

Extraction of the purified nuclei of SV40 infected cells reveals a heterogeneous set of viral DNA-protein complexes. Earlier, the authors have shown the possibility of nuclear particles extraction being indistinguishable from mature SV40 virions. In the present work, structural intermediates of virus maturation from free minichromosomes through replicative complexes to immature virion particles have been analyzed. The fractionation of viral complexes by non-denaturing agarose gel electrophoresis has been employed. The protein composition of the complexes as determined by two-dimensional gel electrophoresis indicates that five histone fractions including H1 are present during minichromosome maturation to the chromosome of the mature virion.     

Studies on protein kinases in two human rectocolic cell lines by polyacrylamide gel electrophoresis.Effect of the vasoactive intestinal peptide

Electrophoresis and subsequent assay of the enzyme directly onto the gel has allowed a rapid and quantitative characterization of the cyclic AMP-dependent and -independent histone kinases, protamine, phosvitin and casein kinases in HT 29 and HRT 18 cells. The technique has been applied to soluble extracts from cytoplasmic and nuclear fraction prepared in the presence and absence of neutral detergent. A more precise identification of these enzymes has been possible by analysing enzyme fractions obtained after ion-exchange chromatography of the above extracts. The protein kinase equipment of both cell lines was found to be identical (11 major components) but with different relative proportions of several enzymes. In cytoplasmic extracts: VIP activates only the type I, cytosolic, (band 4) and the type II, membrane-bound, (bands 6 and 8) cyclic AMP-dependent histone kinases. These enzymes account, respectively, for 34 and 55% of the total histone kinases in HT 29 and HRT 18 cells. The cyclic AMP-independent histone kinases (band 1,2,5 and 7) also phosphorylate protamine; band 5 was found 3o be much higher (4-fold) in HT 29 cells. In addition, two casein/phosvitin kinases have been identified in both cell lines with phosphorylating activity similar to the total histone kinases. In the nuclear extract two cyclic AMP-independent histone kinases have been found with electrophoretic mobility differing from the cytoplasmic enzymes. Also, two phosvitin/casein kinases specifically nuclear, due to their chromatographical and electrophoretical behaviour, have been characterized.     

Fractionation of non-histone chromatin proteins from pig liver and kidney by means of immobilized histone H3

Summary The non-histone chromatin proteins (NHCp) from pig liver and kidney have been partially fractionated in non-denaturing conditions by the use of histone H₃ immobilized on agarose and the fractions obtained have been analysed by SDS-polyacrylamide gel electrophoresis and amino acid analysis. At least six different fractions have been obtained by successive increases of the ionic strength of the medium. Few NHCp have been evidentiated with subunit molecular weights 55,000 and less than 30,000, which display a remarkably high affinity for histone H₃, and require 5 M urea to be displaced from the immobilized histone. The elution patterns of the NHCp from liver and kidney, although very similar, reveal some significant differences between the two tissues, which are undetectable by SDS-electrophoresis and which are most likely due to tissue specific proteins. This histone-affinity chromatography appears to be a promising approach for the analysis of specific histone-NHCp interactions, and as a first step for NHCp purification.     

Some Researches on Histones

The histone extracted from calf thymus glands is a complex system of proteins, which can be fractionated by chromatography on carboxymethyl cellulose columns into three principal fractions (1) very lysine-rich, (2) moderately lysine-rich, (3) arginine-rich. When examined by starch gel chromatography each of these gives more than one band. Methods have been devised for further separation of the components in some cases. The components show characteristic differences in end groups and certain amino acids as well as in their basic character. Histones extracted from various rat tissues can be separated into similar fractions, of which the amino acid analyses are similar to those derived from calf thymus, within the experimental error. To this extent, no species or tissue specificity of the fractionated histones was observed. Although all the histone fractions contain approximately one basic amino acid to three non-basic amino acids their structure is not regular, as Phillips has shown that in certain fractions the number of non-basic groups between two basic groups may vary from 0 to seven or more. The possible functions of histones are discussed.     

Structural characteristics of lysine-rich histone from the sperm of a mollusk Anodonta piscinalis

Sperm of freshwater bivalve mollusk Anodonta piscinalis was found to contain two fractions of lysine-rich histone: somatic histone H1 and sperm-specific protamine-like histone, named Hp. A detailed analysis of H1 and Hp structure was carried out by means of N-bromosuccinimide, chymotrypsin and pepsin cleavage followed by determination of the lysine residue number, positive charge and molecular length of obtained fragments by the method of incomplete succinylation. It has been shown, that Anodonta histone H1, like the avian histone H5, contains 3 tyrosine residues in the central hydrophobic domain of the molecule. Histone Hp contains 5 tyrosine residues, 3 of which are localized in the hydrophobic domain, while the rest two--in the COOH-terminal part of the molecule, characterized by a strong positive charge. Such unusual disposition of tyrosine residues in the lysine-rich histone has been found for the first time. All the regions of histone Hp molecule contain a great number of arginine residues. The only phenylalanine residue is localised approximately in the middle of the polypeptide chain for both H1 and Hp molecules. On the basis of structure homology between histones H1 and Hp the origin of Hp from H1 in the course of evolution is proposed.