New histones found in mature mammalian testes.

Abstract

Two new histones have been found in sexually mature testes of several mammals. The new histones have been identified as a new F1 (TFI) and F2b (TF2b) on the basis -of their behavior upon chemical fractionation procedures and electrophoresis at several urea concentrations. The new testis-specific histones are absent in very immature animals and in somatic tissues. However, by day 20, in the rat, the histone pattern is that of the adult, displaying nearly a full complement of TF1 and TF2b. The new histone complement evidently is characteristic of prespermatid germ cells. The degree of evolutionary variations in these histones and in other basic sperm proteins, as detected by change in electrophoretic mobility, appears to be much greater than that seen in somatic histones. The process of spermiogenesis involves the production of a haploid genome, packaged in a highly organized and compact fashion. In echinoderms the compact nucleoprotein contains DNA in association with histones which are either identical or similar to those found in somatic cells (1-4). On the other hand, in arthropods and teleosts somatic histones are replaced in mature spermatozoa by a low molecular weight, arginine-rich class of proteins known as protamines (5, 6). Early studies of mammalian species indicated that there was a shift toward an arginine-rich nucleoprotein during spermiogenesis, and indeed several workers have isolated small basic proteins from spermatozoa. Coelingh et al. isolated and sequenced a protein of molecular weight about 6000 from bull spermatozoa which contained large amounts of arginine and cysteine (7,8). Kistler et al. have described another nuclear protein (MW about 6200) isolated only from mature rat testes, but which is not present in rat spermatozoa (9, 10).We initiated a program designed to compare the basic proteins from spermatozoa of a range of mammals. As Protamines were obtained from the headpieces of mature spermatozoa isolated from the testis, intact epididymis, or semen. The headpieces were separated from the tails of the spermatozoa by blending. During the acid extraction of the histones from the nuclei, the sperm heads were precipitated t To whom reprint requests should be made.in the acid-insoluble fraction. The pelleted sperm heads were washed twice with deionized water, suspended in 15-20 ml (1 ml/g of starting tissue) of 5 M guanidine-hydrochloride, 0.5 M 2-mercaptoethanol, and homogenized. The ensuing gel was adjusted to pH 7 with NaOH and sheared in a Virtis model 45 homogenizer at 70 V for 45 sec. The ionic strength was decreased by adding 2.5 volumes of deionized water. Protamines were extracted in 0.2 M H2SO4 at 40 for 2 hr. After centrifugation at 27,000 X g for 20 min, the supernatant was dialyzed against 0.2 M H2SO4 to remove guanidine-hydrochloride.The bull protamine was obtained from spermatozoa isolated from bull semen, utilizing a slightly modified procedure of Marushige and Marushige (13).Electrophoresis of histones was performed on 15% acrylamide gels as described (14). Elec...

Meiotic synthesis of testis histones in the rat.

“…Two of them, THi (3,19), but the two histones have significant differences in their lysine and valine contents. TH2B is a variant of H2B (4), as demonstrated by amino acid analysis, molecular weight determinations, and chemical fractionation. The main difference between them is that TH2B contains cysteine.…”

“…In this paper we describe the appearance, synthesis, and turnover of two testis-specific histones, testis H1(TH1) and testis H2B (TH2B); these histones are closely related, by molecular weight and amino acid composition, to the somatic histones H1 and H2B, respectively (3,4).…”

Structure of human nucleosome containing the testis-specific histone variant TSH2B

“…The mammalian histone H2B variant TSH2B was initially found in histone extracts from rat testes (Branson et al, 1975;Shires et al, 1975). Genomic and genetic analyses revealed that the mouse TSH2B homologue, TH2B, functions in genome-wide histone-protamine exchange during spermatogenesis (Govin et al, 2007;Montellier et al, 2013).…”

A model for the structure of chromatin in mammalian sperm.

“…Concomitant with these visible changes in chromatin organization, the histone and nonhistone proteins are removed from the DNA and replaced for a period of time by several transition proteins . These proteins are subsequently replaced by protamine during the final stages of spermatid maturation, chromatin reorganization and condensation (11,12,14,35,36,48,56,61,71,76,78,85) .…”