Species variability of N-terminal sequence of avian erythrocyte-specific histone H5

The N-terminally acetylated form of mammalian histone H1(o), but not that of avian histone H5, increases with age

We report here on the HPCE separation of two chicken H5 histones, which do not show the heterogeneity (Gln/Arg) at residue 15 first found by Greenaway and Murray [Greenaway and Murray (1971) Nat. New Biol. 229, 233-238]. The two subfractions obtained were identified using reversed-phase HPLC, hydrophilic interaction HPLC, Edman degradation, and MALDI-MS analysis. We found that the two H5 subcomponents differ only by an acetylated (designated H5a) and an unacetylated N-terminus (H5b). In contrast to the N-terminally acetylated form of rat kidney histone H1(o), which increased by about 40% with aging of the animal, the corresponding form of chicken H5 did not: the ratio N-terminally acetylated: unacetylated remained constant (30:70) when histone H5 was extracted from erythrocytes of newly hatched chickens and from adult chickens, respectively. The HPCE technique used in this investigation represents a quick and convenient method for analyzing N-terminally acetylated proteins in the presence of unacetylated forms.

The occurrence of a mutant dimerizable histone H5 in Japanese quail erythrocytes

An allelic variant of linker histone H5 has been found in the erythrocytes of Japanese quail (Coturnix japonica) descended from a small group of feral birds captured on the island of Hawaii. This variant spontaneously forms protein dimers in vitro in the absence of reducing agents. That this depends upon the introduction of a sulfhydryl group (presumably because of a cysteine substitution) is indicated by its reaction with 2-nitro-5-thiocyanobenzoate and by its fluorescence after reaction with 4-aminosulfonyl-7-fluoro-2,1,3-benzoxadiazole. This is the first reported example of cysteine in a vertebrate linker histone and offers a specific reactive site for structural studies. A homozygous line for this form of H5 is being developed.

A comparison of the histone H1 complements of avian erythrocytes

1. Histone H1 from chicken, turkey, duck and goose erythrocytes was resolved into six bands and that from quail into seven bands in an acetic acid-urea polyacrylamide gel. 2. A fast migrating minor subtype H1.e was detected in avian erythrocytes using two-dimensional polyacrylamide gel electrophoresis. 3. Although histone subtype H1.z from quail, turkey and duck was well separated in acid-urea gel, a similar protein in goose was found only in two-dimensional gel. This spot was absent in chicken. 4. Histone H1 spots .c, .c' and .d migrate in two-dimensional gel in a relatively constant manner forming a triangle-shaped pattern that facilitates comparison of H1 subtypes among various avian species.

Use of protein blotting to study the DNA-binding properties of histone H1 and H1 variants

Sub-types of histone H1 have been observed in a variety of tissues from several organisms. One of the best characterized H1 variants is H5 from avian erythrocytes. Several lines of evidence suggest that H5 has a greater affinity for DNA than H1 and is thus thought to account, in part, for the highly condensed and transcriptionally repressed state of avian erythrocyte chromatin. In trout there is an analogous erythrocyte-specific H1 variant, previously termed 'H5' [B.L.A. Miki and J.M. Neelin (1975) Can. J. Biochem. 53, 1158-1169). Using a sensitive and rapid protein-blotting procedure which is specific amongst the histones for histone H1 and its variants, we compared DNA-binding properties of the trout erythrocyte histone 'H5' and chicken H5. By increasing the NaCl concentration of the binding buffer, a gradual decrease in the amount of DNA that bound to chicken H1, trout H1 and trout erythrocyte 'H5' variant was observed, such that at concentrations above 0.37 M, negligible amounts of DNA were bound. By contrast, chicken H5 bound a significantly greater amount of DNA even at a concentration of 0.4 M NaCl. Based on the DNA-binding, properties, we conclude that the trout erythrocyte variant 'H5' is more closely related to H1 than to H5. By assaying the DNA-binding affinity of calf thymus H1 DNA-binding affinity of calf thymus H1 peptide fragments, generated by protease and chemical cleavage, and the sperm-specific H1 variants of the annelid, Platynereis dumerilii, which possess greatly shortened C-terminal tails, we conclude that a domain that includes a very small portion of the C-terminal tail and part of the globular domain is sufficient for the binding of H1 to DNA.

Predictability of sequence homologies among lysine-rich histones by immunological distance

The relationship between immunological distance (I.D.) measured by microcomplement fixation and amino acid sequence difference for lysine-rich histones was tested using antisera to lysine-rich histones of known sequence, chicken H1 and H5, goose H5, and trout H1 as well as to trout H5. The best relationship between I.D. (y) and percent sequence difference (x) for lysine-rich histones, y = 2x, applies as well to other histones of known sequence but it differs from y = 5x, reported for other proteins and often used for histones. Although deviations indicate that I.D. is a poor predictor of primary sequence differences among histones, it suggests that trout H5 is more closely related to H1 than to chicken H5.

Conserved dyad symmetry structures at the 3' end of H5 histone genes. Analysis of the duck H5 gene

The duck H5 histone gene and its flanking DNA have been isolated and sequenced. S1 nuclease mapping reveals that transcription starts 149 nucleotides upstream of the initiation codon and that the site of polyadenylation is located 200 nucleotides downstream of the termination codon. A comparison with the chicken H5 gene demonstrates that the 3' non-translated segment of the polyadenylated H5 mRNA carries two conserved dyad symmetry sequences. The first potential hairpin is located directly after the termination codon of the H5 gene and is highly conserved, whereas the second stem and loop structure maps shortly upstream of the polyadenylation site and shows a homology block at the central part of this inverted DNA repeat.

A survey of H1o-and H5-like protein structure and distribution in higher and lower eukaryotes

A survey of H1o and H5-like proteins has been conducted through a range of higher and lower eukaryotic species. All mammals examined possessed H1o proteins, although in variable amounts, and the protein's structure was well conserved, though not invariant. The testis-specific histone Hlt (from rat) did not have an H1o-like structure and it appears that H1o does not occur in spermatocytes in any form. The results also show that Xenopus laevis contains H1o-like proteins, but lower, non-vertebrate eukaryotes (a crustacean, two fungi and a plant tissue) do not possess H1o or H5 proteins. The evidence suggests that H1o and H5 proteins may be considered as belonging to one family, distinct from H1 types. This H1o/H5 family may well be 'replacement histone' variants of H1. The results do not support suggestions of roles such as repression of DNA synthesis or of transcription for H1o/H5 proteins.

Isolation from trout liver of a methionine-containing H1 subfraction, THImet

A trout H1 subfraction, THImet, which contains one residue of methionine and a blocked N-terminal amino acid, has been isolated from trout liver. Cyanogen bromide cleavage of THImet and amino acid analysis and polyacrylamide gel electrophoresis of the cleavage products show that it contains a residue of methionine at about the same distance from the N terminus as mammalian H1o and avian H5. THImet is shown to be similar to, but not identical with, the protein derived from trout erythrocytes generally accepted as the equivalent in fish of avian H5.

Is histone H5 present in mammals?

An extraction procedure for histone H5 for chicken erythrocytes described in the literature has been applied to mouse spleen. The SDS polyacrylamide gel electrophoresis pattern of the resulting protein preparation revealed the presence of a component with the mobility of the marked chicken erythrocyte H5. Additionally the preparation has been characterized using antiserum raised against purified chicken H5. The presumptive mouse spleen H5 preparation gave visible precipitation lines with the anti-H5 chicken-antiserum. The combined electrophoretic and immunological evidence suggests the presence of histone H5 in mammalian tissue.

Cell-specific antigens in chicken erythroid nuclei: species specificity

Antisera raised to dehistonized chicken reticulocyte chromatin were tested for their cell and species specificity. Quantitative microcomplement fixation and immunohistochemical localization revealed the presence in chromatin of erythroid cell-specific nonhistone protein antigen(s). The antigenic specificity was shown to depend on the association of the antigenic protein(s) with deoxyribonucleic acid (DNA). Although the antisera were exceptionally cell specific, they cross-reacted with erythroid cells of other avian species. The extent of cross-reactivity was found to approximate the phylogenetic distances of the tested avian species. Erythroid cells from fish and amphibians were not reactive. Reconstitution experiments of partially purified chicken reticulocyte chromosomal nonhistone protein antigens with DNAs isolated from several vertebrate species showed that the species specificity of the antigenic complexes is determined principally by the species origin of the nonhistone proteins. Our results show that a cell-specific chromosomal nonhistone protein(s) has undergone evolutionary change and the relative immunological differences are consistent with the accepted phylogenetic distances of the species examined.

Phosphorlyation of H1 and H5 histones by cyclic AMP-dependent protein kinase reduces DNA binding

Phosphorylation of H1 histones by cyclic AMP-dependent protein kinase may be an important transcriptional control mechanism. We have used affinity chromatography to examine the effect of phosphorylation by this enzyme on the DNA-binding properties of calf thymus H1 histones and two highly basic H1 homologues from condensed and transcriptionally silent nuclei: duck erythrocyte H5 and Strongylocentrotus purpuratus sperm H1. Without in vitro phosphorylation, all three histones were eluted from native DNA-Sephadex G-25 columns at salt concentrations which closely resembled those required to extract these histones from nuclei or chromatin. When a small portion of radioactively phosphorylated histone was chromatographed with untreated carrier histone, the phosphorylated species was consistently eluted from the DNA column at slightly lower salt concentrations than the main histone peak. Rechromatography experiments showed that in vitro phosphorylation of H1 can shift its elution position to lower salt concentrations.

A purification and some properties of two proteases from papaya latex

Two proteases, one of which is papaya peptidase A and the other a previously unknown enzyme in papaya latex have been purified to homogeneity in a simple two stage process. Both are markedly less reactive than papain or chymopapain. Each has a molecular weight of 24,000, N-terminal sequences commencing Leu-Pro-Glu, and contains no carbohydrate. Their amino acid compositions differ for several residues. The essential -SH groups of the enzymes examined appear to be 'masked' in the native state.

Purification and preliminary characterization of two asclepains from the latex of Asclepias syriaca L. (milkweed)

Two groups of asclepains have been isolated from Asclepias syriaca L. (milk-weed) latex and a representative of each has been purified. Asclepains A3 and B5 are homogeneous proteins with molecular weights of 23 000 and 21 000, respectively. Both require a reducing and chelating agent for maximum activity and hydrolyze ester, amide and peptide bonds. The optimum pH for hydrolysis of casein is 7.5 to 8.5 for asclepain A3 and 7.0 to 7.5 for asclepain B5. Both enzymes are autolytic when active and are inhibited by p-chloromercuribenzoate, iodoacetic acid and sodium tetrathionate. Asclepains A3 and B5 each contain one titratable SH group per molecule and no bound carbohydrate. Each of the two enzymes has leucine as the N-terminal amino acid. There are notable differences in their amino acid compositions.

Amino acid sequence homology between histone H5 and murine leukemia virus phosphoprotein p12

The amino terminal acid sequences of several mouse leukemia virus phosphoproteins (p12) show definite homology with the amino terminal conserved region of H5 histones, the phosphorylated nuclear proteins of nucleated erythrocytes. Differences in the amino acid compositions of the two groups of proteins seem to rule out the possibility that they evolved from a single common ancestral gene. The finding of sequence homology between viral p12's and cellular histones, however, is consistent with evolution of retrovirus structural proteins by a process of differentiation from preexisting cellular genes. The conserved primary and secondary structure at the amino terminal region, common to both groups of proteins, may be related to their common function of nucleic acid binding modulated by phosphorylation.

Histones of Xenopus laevis erythrocytes. Purification and characterization of the lysine-rich fractions

Lysine-rich histones have been isolated from the terminally differentiated erythrocytes of Xenopus laevis. Three major proteins have been separated by ion-exchange chromatography. These proteins have been characterized by electrophoresis, amino acid analysis and immunochemical techniques. It is concluded that two 'typical' lysine-rich subfractions are present in Xenopus erythrocytes and, in addition, a serine-rich histone, that shares no common antigenic determinants with the other lysine-rich histones.

Histone H5 in nucleated erythrocytes of fish as determined by radioimmunoassay

Tissue-specific histone H5 in the nucleated erythrocytes of dogfish, scup, skate, tautog, sea robin and toad fish was studied. The presence of this histone was inferred by its electrophoretic mocility on polyacrylamide gels containing either acid-urea or sodium dodecyl sulfate. By radioimmunoprecipitation assays, cross reaction was observed between fish histones and an anti-H5chicken antibody. The antibody was specific to chicken histone H5; purified chicken histone H1 and calf thymus total histones did not cross react. It is concluded that fish histone H5 shares common antigenic determinants with the chicken H5 histone.