Histone differentiation and nuclear activity

Transition of basic protein during spermatogenesis of Fenneropenaeus chinensis (Osbeck, 1765)

According to the ultrastructural characteristic observation of the developing male germ cells, spermatogenesis of the crustacean shrimp, Fenneropenaeus chinensis, is classified into spermatogonia, primary spermatocytes, secondary spermatocyte, four stages of spermatids, and mature sperm. The basic protein transition during its spermatogenesis is studied by transmission electron microscopy of ammoniacal silver reaction and immunoelectron microscopical distribution of acetylated histone H4. The results show that basic protein synthesized in cytoplasm of spermatogonia is transferred into the nucleus with deposition on new duplicated DNA. In the spermatocyte stage, some nuclear basic protein combined with RNP is transferred into the cytoplasm and is involved in forming the cytoplasmic vesicle clumps. In the early spermatid, most of the basic protein synthesized in the new spermatid cytoplasm is transferred into the nucleus, and the chromatin condensed gradually, and the rest is shifted into the pre-acrosomal vacuole. In the middle spermatid, the nuclear basic protein linked with DNA is acetylated and transferred into the proacrosomal vacuole and assembled into the acrosomal blastema. At the late spermatid, almost all of the basic protein in the nucleus has been removed into the acrosome. During the stage from late spermatid to mature sperm, some de novo basic proteins synthesized in the cytoplasm belt transfer into the nucleus without a membrane and almost all deposit in the periphery to form a supercoating. The remnant histone H4 accompanied by chromatin fibers is acetylated in the center of the nucleus, leading to relaxed DNA and activated genes making the nucleus non-condensed.

Protamine-like proteins: evidence for a novel chromatin structure

Protamine-like (PL) proteins are DNA-condensing proteins that replace somatic-type histones during spermatogenesis. Their composition suggests a function intermediate to that of histones and protamines. Although these proteins have been well characterized at the chemical level in a large number of species, particularly in marine invertebrates, little is known about the specific structures arising from their interaction with DNA. Speculation concerning chromatin structure is complicated by the high degree of heterogeneity in both the number and size of these proteins, which can vary considerably even between closely related species. After careful examination and comparison of the protein sequences available to date for the PL proteins, we propose a model for a novel chromatin structure in the sperm of these organisms that is mediated by somatic-type histones, which are frequently found associated with these proteins. This structure supports the concept that the PL proteins may represent various evolutionary steps between a sperm-specific histone H1 precursor and true protamines. Potential post-translational modifications and the control of PL protein expression and deposition are also discussed.

Model system studies of staining procedures for lysine and arginine residues

Using polyacrylamide films containg poly-lysine, polyarginine and DNA as test models, a variety of reportedly specific staining procedures have been examine. Contrary to published observations, mixtures of fast green and eosin Y show no specific staining of either lysine or arginine. Both amino-acids bind eosin from the mixture more strongly than fast green. Arginine apparently has a greater affinity for this eosin than has lysine which contradicts previous reports that lysine will be stained by eosin arginine will stain with fast green, if proteins containing both amino-acids are stained with dye mixture. In films containing lysine and/or arginine picric acid is shown to bind specifically to the arginine. The picric acidarginine complex resists disruption in 0.004 M borate buffer which is a solvent used for subsequent staining of lysine residues with bromophenol blue. Picric acid may also be used as a hydrolysant and substitute for hydrocholoric acid in a Feulgen-like procedure which stains DNA to the same level as the classiclal hydrochloric acid based procedure while also staining arginine present.

Cytochemical evaluation of the Guard procedure a regressive staining method for demonstrating chromosomal basic proteins. I. Effects of fixation, blocking reactions, selective extractions, and polyacid "differentiation"

Appropriately fixed preparations stained by a modification of the Guard (1959) reaction for "sex chromatin" display selective staining of interphase chromatin and mitotic or meiotic chromosomes. This is a regressive staining method which seems to depend on the selective displacement of an acidic dye from less basic structures, and retention of the dye at more basic sites. The results obtained with the reaction can be controlled by the length of time that the preparations are "differentiated" in solutions containing phosphomolybdic and phosphotungstic acids (polyacids). After three- or four-hour exposures to polyacid solutions, all chromatin is stained. However, with longer differentiation, "condensed" chromatin can be stained preferentially. Of a number of fixatives investigated, only 10% formalin, ethanol-acetic acid (3:1), and Bouin's solution proved useful. Others resulted in diminished specificity or a total loss of selectivity. The most intense staining was obtained after formalin fixation. Less intense dyebinding was observed after fixation in 3:1 - probably due to extraction of some histone fractions-and the least amount of dye was bound in Bouin's-fixed chromatin - probably due to blockage of arginine residues by picric acid. The reaction was not affected by enzymatic removal of nucleic acids or the extraction of lipids. It was diminished by treatment with trypsin or weak acetylation, and it was completely prevented by strong acetylation, deamination, or extraction of basic proteins with HCl. The results presented suggest that the modified Guard (1959) procedure selectively demonstrates basic nucleoproteins. Further, by the use of regressive differentiation in polyacid solutions, the retention of dye in more condensed chromatin can be favored.

A kinetic study of DNA and basic protein metabolism during spermatogenesis in the sand crab, Emerita analoga

Cytochemical and radioautographic techniques define and confirm a staging scheme for developing spermatids of the decapod crab, Emerita analoga. Quantitative photometric data demonstrate that developing spermatids lose a significant proportion of their nuclear proteins, as evidenced by diminishing binding of fluorodinitrobenzene. Photometric results also show that much (but not all) of the spermatid nuclear protein loss is in somatic-type histone, as evidenced by a dramatic fall in the histone/DNA ratio of these cells during a period in which nuclear DNA content remains constant. By the end of spermiogenesis, the sperm nuclear histone and protamine content is approximately zero, whereas some nonbasic protein persists. Loss of spermatid nuclear somatic-type histone is not accompanied by synthesis of gamete-type histone (e.g. protamine or arginine-rich histone), showing that the processes of displacement and synthesis of nuclear basic proteins during histone transition are not subject to obligatory coupling. Labeling studies suggest that nonbasic acrosomal proteins (presumably partly enzymes) are synthesized in the cytoplasm, after which they move into the acrosome. Stainable basic proteins accumulate in the acrosome during precisely the period of nuclear somatic histone loss, suggesting nuclear-cytoplasmic transfer.

Isolation and characterization of chromatin from Neurospora crassa

Different preparations of chromatin isolated from mycelia of Neurospora crassa were analyzed for DNA-associated RNA and proteins. The UV absorption spectra, the ultrastructure of chromatin, and the amino acid composition of the acid-extractable proteins were studied. The protein:DNA ratios range from 1.5 to 2.8; the RNA:DNA ratios range from 0.5 to 1.24. UV absorption shows a macimum at 259 mmicro and a minimum at 238-239 mmicro. The E280/E260 ranges from 0.59 to 0.70. Electron microscopy reveals a fibrous structure with individual fibers of 120-150 A average diameter. Attempts were made to study the protein by polyacrylamide gel electrophoresis and amino acid analysis. The results indicate that Neurospora chromatin does not contain basic proteins comparable to calf thymus histone. The ratios of basic to acidic amino acids range from 0.93 to 1.19. On electrophoresis, no bands are seen whose positions correspond to those of histones. Staining for basic proteins with fast green or eosin Y at pH 8.2 also shows a negative reaction, suggesting the absence of histones.

RNA and protein in nucleolar structures of dragonfly oocytes

Dragonfly and damselfly oocytes regularly contain two nucleolus like bodies of different sizes, a primary nucleolus and a secondary nucleolus. The primary nucleolus stains more deeply with RNA stains than with an arginine stain; the seconidary nuicleolus stains conzversely. The primary nulcleolus incorporates uridine under all conditions tested; the secondary, only after precautions have been taken to preserve soluble RNA. Both inicorporate lysine.