Non-histone chromosomal proteins. Evidence for their role in mediating the binding of histones to deoxyribonucleic acid during the cell cycle

Direct and cost-effective method for histone isolation from cultured mammalian cells

Histones are an essential part of nucleosomes that regulate chromatin structure and function. Histone exchanges and modifications represent a scaffold for DNA transcription, repair, and replication. Studying histones and histone code is an important and fast-developing branch of epigenetic science. Here we propose a fast, efficient, and versatile assay for nucleosomal histone isolation from mammalian cells, without the use of acids or high salt solutions which are common for other histone isolation techniques. All components used in the protocol are common and inexpensive laboratory chemicals. The protocol has been evaluated on six commonly used cell lines and two animal tissue samples. The mild extraction conditions preserve delicate histone epigenetic changes, allowing its downstream analyses. We have demonstrated the assays' successful application during changes in the transcriptional activity of histone genes, cell cycle transitions, and DNA-damaging conditions. Histone fractions, obtained by the protocol, can be used for further applications, such as electrophoresis, immunoblot, and mass spectrometry. Therefore, the new proposed nucleosomal histone isolation method is sensitive, specific, and suitable for downstream applications of various kinds.

Incorporation of various amino acids into non-histone chromatin protein fractions of spleen cells of mice immunized with IgG

Incorporation of three various amino acids ([3H]-tryptophan, [3H]-methionine or [3H]-leucine) into the non-histone chromatin proteins, synthesized in spleen cells of mice after immunization with IgG, is described. Two new fractions of non-histone chromatin proteins (I-mol. wt. below 3 000 and B1-mol. wt. about 120 000), appearing during the immune reaction were labelled with [3H]-tryptophan and [3H]-methionine but not with [3H]-leucine. Synthesis of these fractions was observed only at the time of maximal RNA synthesis. A suggestion about the role of tryptophan and methionine in non-histone chromatin proteins in the regulatory processes of gene activation is discussed on the basis of their selective binding to DNA.

Regulation of specific genes during the cell cycle. Utilization of homologous cDNAs and cloned sequences for studying histone gene expression in human cells

Evidence for differential gene expression during the cell cycle and approaches for studying cell-cycle-stage specific gene expression are summarized. Attention is focused on regulation of histone gene expression during the cell cycle of continuously dividing cells and after stimulation of nondividing cells to proliferate. The level(s) at which control of histone gene expression occurs and the possible involvement of chromosomal proteins in the regulation of histone gene expression are discussed. The preparation of cloned human histone sequences and their use in studying the structural and functional properties of human histone genes are presented. Index Entries: Cell cycle, gene regulation during; gene regulation, during the cell cycle; regulation of specific genes, during the cell cycle; DNAs, homologous, and histone gene expression; cloned DNAs, and histone gene expression; histone gene expression; gene expression, histone; cloned human histone sequences.

On mechanisms determining the interrelationships between DNA and histone components of chromatin

The relative affinity of histones for DNA was studied by the analysis of competitive histone binding to DNA in whole histone/DNA mixtures at physiological and low ionic strengths as well as in water. Use of polyphosphate in similar experiments, as a model of DNA deprived of hydrophobic functional groups allowed us to reject the hypothesis that hydrophobic DNA-histone interaction plays a decisive role in the determination of the relative affinity of histones for DNA, because the orders of histone preference for DNA and for polyphosphate were the same. The relative histone affinity for DNA does not depend on the secondary structure of DNA or on the ionic strength of salt solutions, though the differences in the histone affinities for DNA decrease on lowering the salt concentration. The binding orders of the first and the last molecules of histone type to DNA, studied at various DNA/histone ratios in the medium of physiological ionic strength, are the following: H3+H4, H2A+H2B, H1 and H3+H4, H2A, H2B, H1. In water the binding orders of the first and the last histone molecules to DNA are identical: H3+H4, H2A, H2B+H1. It is concluded that the relative histone affinity for DNA in water/salt solutions is determined by non-ionic interactions between histones bound to DNA. The folding of DNA induced by histone-histone interaction seems to lead to the increase in the correlation between amino acid residues in the histone regions bound to DNA and the ionic DNA-histone interaction becoming stronger.

Cellular localization of the apurinic/apyrimidinic endodeoxyribonucleases in rat liver

A method has been developed to purify rat liver nuclei; the isolated nuclei keep both nuclear membranes and retain more than 90% of the cell apurinic/apyrimidinic (AP) endodeoxyribonuclease activity. The nuclear enzyme is located mostly in chromatin non-histones; there is also an important amount of activity in the nuclear sap and some in the nuclear membranes. The cytoplasmic AP endodeoxyribonuclease activity is shared between mitochondria, cytosol and membranes. Different cell compartments appear to contain different AP endodeoxyribonuclease species: the membrane enzyme is activated by Triton whereas the other enzymes are rather inhibited; the nuclear sap enzyme has a higher molecular weight and a higher thermal resistance than the chromatin enzyme. A hypothesis is formulated according to which: (1) the chromatin enzyme is the only species important for nuclear DNA repair; (2) the species present in the other cell compartments might be precursors of the chromatin AP endodeoxyribonuclease.

[Study On The Chromosomal Proteins Of Fasciola Hepatica]

In attempt to investigate histone fractions and non-histones of parasites, nuclei were isolated from Fasciola hepatica by the procedure of Pogo et al. (1966). Histone fractions H1, H2a, H2b, H3 and H4 were prepared from isolated nuclei by the procedure of Johns (1964 and l967). The five histone fractions found in most tissues were also present in the Fasciola hepatica histones. These histone fractions were characterized by amino acid analysis and by polyacrylamide disc gel electrophoresis. Non-histone proteins were extracted from isolated Fasciola hepatica nuclei and separated by SDS-polyacrylamide gel electrophoresis. The results of the experiment were summarized as follows: 1. The yield of whole histone recovered was 2.47 mg per 1 g of Fasciola hepatica. 2. The yield of DNA was 1.02 mg per gm of tissues. Consequently the DNA to histone ratio was 1:2.44. 3. The relative amounts of five fractions, i.e., Hl, H2a, H2b, H3 and H4 were 19.96%, 26.48%, 29.60%, 12.56% and 14.37%, respectively. 4. Amino acid analysis of the individual histone fractions showed that the over-all compositions were similar but not identical to those of corresponding fraction from calf thymus. 5. It was found that histone H2b fraction of Fasciola hepatica contained detectable amounts of epsilon-N-monomethyllysine. No evidence for the presence of methylated lysine or other side-chain derivatives was reported on this histone fraction. 6. In SDS-polyacrylamide disc gel, it showed that 17 protein bands of nuclear acidic protein can be identified visually.

Nuclear proteins. V. Studies of histone-binding proteins from mouse liver by affinity chromatography

We examined four extracts of mouse liver for histone-binding proteins using histone affinity chromatography and positively charged resins. The extracts used were cytoplasm and washes from isolated nuclei with buffers containing 0.05 M Tris, 0.15 M NaCl or 0.35 M NaCl. Proteins from the nuclear washes showed greater binding to the columns than proteins from the cytoplasm. The binding fractions were heterogeneous in gel electrophoresis systems. Proteins bound to affinity columns of individual histones were similar to those bound to columns of whole histone, polylysine and DEAE. A 25,000 dalton polypeptide (J2), found only in nuclear washes was a prominent histone-binding protein. It could be competitively eluted from DEAE with histones, suggesting polypeptide J2 may show a specific affinity for histones. Polypeptide J2 has an acidic to basic amino acid ratio of 1.58, and its amino acid composition is not similar to that of the high mobility group 1 protein. Polypeptide J2 binds to hydrophobic columns and may play a role in modifying histone-histone and histone-DNA interactions.

Effect of histones and nonhistone chromosomal proteins on the transcription of histone genes from HeLaS3 cell DNA

To elucidate the manner in which histones and nonhistone chromosomal proteins interact to render histone genes transcribable in HeLa S3 cells, we have examined transcription of histone mRNA sequences from DNA, as well as from several DNA-chromosomal protein complexes. Histone mRNA sequences were assayed by hybridization to a 3H-labeled single-stranded DNA complementary to histone mRNAs. Our results indicate that DNA is an effective template for transcription of histone mRNA sequences and that histones by themselves inhibit transcription from DNA, including transcription of histone genes, in a dose-dependent, nonspecific manner. When complexed with DNA alone, nonhistone chromosomal proteins do not affect the transcription of histone mRNA sequences. However, when associated with DNA in the presence of histones, nonhistone chromosomal proteins are capable of selectively rendering histone genes transcribable. These results suggest a possible role for nonhistone chromosomal proteins in mediating the interactions of histones with DNA to render histone genes transcribable.

The effect of SV40 transformation on the chromosomal proteins of 3T3 mouse embryo fibroblasts

The composition and metabolism of chromosomal proteins-histones and nonhistones chromosomal proteins-were examined in normal and SV40 transformed 3T3 mouse cells. Variations were observed, many of which were similar to those previously reported for normal and SV40 transformed W138 human diploid fibroblasts. The possible implications of these viral induced changes in the protein component of the genome for the phenotypic modifications which occur in transformed cells are discussed.

Autoradiographic study of the penetration of non-histone chromatin proteins into differentiating cells

Attention has previously been drawn to a specific effect of NHCP on embryonic Pleurodeles cell differentiation. With a modified NHCP labelling technique, autoradiography has revealed a cytoplasmic concentration of labelled NHCP and has not revealed any difference between homospecific and heterospecific NHCP penetration.