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M Bustin

Publications and source records attributed to M Bustin.

At least 163 records · Page 9Linked to original sources
PubMed1976

Histone dimers: a fundamental unit in histone assembly.

Histone interactions which occur, at moderate ionic strengths, when several types of purified, renatured histones are mixed at equimolar ratios have been studied. The four histones H2A,H2B,H3 and H4 complex and form dimers. Histone H1 does not interact with the other four histone types and does not form dimers. Mixing of single histone species with preformed histone pairs as well as mixing of two different types of histone pairs, leads to exchange of histones among the pairs and formation of dimers. No trimers are formed. The dimers are in equilibrium with high-molecular weight histone structures. The results indicate that histone dimers may serve as a stable intermediate in histone assembly. Because each histone type (except H1) can interact with itself as well as with each of the other three histone types we suggest that each histone type should be considered as an interchangeable subunit of a multichain protein in which the dimer species is the most stable structure.

Animals↗
PubMed1976

Histone and DNA detection in swollen spermatozoa and somatic cells, by immunofluorescence.

A method of swelling spermatozoa and other cells, which leads to the exposure of nuclear antigens is described. By applying the indirect IFT on these swollen cells with sera containing antibodies to nuclear antigens, and by comparing the results to those obtained in other tests (measuring anti-nuclear antibodies), the following conclusions could be drawn: (a) By swelling human spermatoza, nuclear antigens of the sperm are exposed, and can be used for the detection of antibodies directed against them. (b) Heterlogous antibodies to histones F2al, FIa2 and F3 which can not be detected in the indirect IFT on rat liver cells, become detectable after swelling of these cells. (c) Mature human spermatozoa contain, in addition to double-stranded DNA and protamine, small amounts of histone F2b and F2a2. (d) In mature human spermatozoa histone F1 is absent.

Antibodies, Antinuclear↗
PubMed1975

Dynamic equilibrium in histone assembly: self-assembly of single histones and histone pairs.

The assembly of acid-extracted, purified F2a1, F3, F2a2, and F2b histones and their six possible pairwise combination into organized structures has been studied by: (1) sedimentation velocity, (2) sedimentation equilibrium, (3) electrophoresis in polyacrylamide gels containing sodium dodecyl sulfate after cross-linking the protein solution with dimethyl suberimidate, and (4) electron microscopy. Each of the purified histone fractions can renature and assemble into high molecular weight organized structures. This assembly is dependent on the ionic strength, protein concentration, and temperature of the solutions. The four histones studied assemble into structures of similar dimensions and shape. In each case the first structure observed is a bent rod with a diameter of 22 A. Conditions which favor assembly lead to formation of fibers with diameters of about 44 A. The conditions which lead to assembly into organized structures are similar for the arginine-rich histones, F2a1 and F3. Higher ionic strength is required for the assembly of the lysine-rich histones, F2a2 and F2b. Certain pairs of histones interact. Strong interactions among pairs of histones interfere with the self-assembly of single histones into large structures. Howver, increase in protein concentration or ionic stregth leads to formation of large molecular structures even in solutions of pairs of strongly interacting histones. These structures are similar to those obtained with single histones. The results suggest that aggregation and complexing of histones represent a reversible, ordered process of assembly. The various assembled forms are in a dynamic equilibrium. The final assembled form, which is similar in all cases, is dependent on the environmental conditions to which the histones are exposed. It is suggested that each of the assembled histone structures, regardless whether it is composed of a single histone or a pair of histones, can serve as a core around which the DNA can be wrapped.

Animals↗
PubMed1975

Immunological comparison of basic encephalitogen and histone F2A1.

The extent of immunological cross-reaction between basic encephalitogen and histone F2A1 on both the humoral antibody level and on the cellular level has been established. The extent of humoral cross-reaction was tested by direct complement fixation employing both anti-histone F2A1 and antisera to basic encephalitogen, by inhibition of complement fixation, by radioimmunoassay and by passive cutaneous anaphylaxis. The data obtained failed to reveal immunological cross-reaction at the cellular level was tested by the lymphocyte stimulation technique in rabbits and guinea pigs, by inhibition of lymphocyte stimulation and by delayed hypersensitivity skin reactions. A slight but significant cross-reaction between the two proteins on the cellular level was detected by inhibition of lymphocyte stimulation and by the delayed hypersensitivity test. It is concluded that the immunological studies provide limited evidence that the two proteins share antigenic determinants.

Animals↗
PubMed1975

Exposure of histone antigenic determinants in chromatin.

The exposure of antigenic determinants of histones present in "native" chromatin was studied by: (1) testing their ability to elicit anti-histone antibodies and (2) measuring their ability to interact with anti-histone sera. To this end, antisera specific to purified histone fractions and to purified rat liver chromatin were elicited in rabbits. The anti-chromatin sera did not react with pure histone fractions and pure histone fractions F2b, F3, F2a1, and F2a2 failed to inhibit the complement fixation resulting from the binding of anti-chromatin to chromatin. These results suggest that in native chromatin, determinants in these histones are not immunogenic. Histone F1, however, inhibited the reaction between chromatin and anti-chromatin. Antisera elicited by histone fractions reacted weakly with "native" chromatin. The maximal complement fixations (obtained with 5-10 mug of chromatin DNA) were as follows: 60% with anti-F2b, 20% with anti-F1 and anti-F3, and less than 5% with either anti-F2a1 or anti-F2a2. Studies of the interaction between anti-histone antibodies and chromatin in which chromatin was used as an immunoadsorbent indicated that antibodies against different histones were adsorbed to a different degree by the same amount of chromatin. Differences in the immunoadsorbing capacity between sonicated and nonsonicated chromatin were found. Quantitative adsorbtion studies revealed that in the "native" chromatin structure, antigenic determinants of F1 and F2b were more available to interact with homologous antibody than those of F3 and F2a1 and that determinants in F2a2 were the least available. It could be calculated that the "equivalent antigenicity" of the histones in chromatin was 9.6% for F1, 3.2% for F2b, and 0.90% for F3 and F2a1. Upon sonication these values did not change for F1 but increased two-, three-, and fourfold for F2b, F3, and F2a1, respectively. Digestion of chromatin with trypsin totally abolished the ability of chromatin to adsorb anti-histone antibodies.

Animals↗
PubMed1974

Self assembly of histone F2a1.

Purified F(2)a(1) histone molecules assemble into organized structures observable by electron microscopy. The basic structure observed at pH 8 and ionic strength of 0.15 has the shape of a bent rod with an average width of 22 A. The average circumferential length of the rod is 220 A and the average distance between the tips of the rod is 150 A. When the ionic strength is increased the rods align lengthwise into intertwined fiber-like structures. In some cases bent rods assemble "face-to-face" to give circular structures. At high protein concentrations the long fibers form paracrystalline arrays. Examination of these arrays by optical diffraction yielded a meridional reflection with a spacing of 150 A. The main additional reflections are compatible with a structure having a repeat unit of 300 A. We suggest that in chromatin the DNA is packed around organized periodic histone structures and that the periodicity of the histone structure may dictate the periodicity of the repeating unit in chromatin.

Centrifugation, Density Gradient↗