Changes in nuclear content of protein conjugate histone H2A-ubiquitin during rooster spermatogenesis

Electrophoretic analysis of acid-soluble chromosomal proteins isolated from rooster testis cell nuclei at different stages of spermatogenesis, revealed that the nuclear content of a protein identified by its solubility, electrophoretic mobility and amino acid analysis as the protein conjugate histone H2A-ubiquitin (uH2A, A24) changed markedly from meiotic cells to late spermatids. The protein was not detectable in tetraploid primary spermatocytes; it was present in 1.7% of the total amount of nucleosomal core histones in early spermatids and reached its maximum level (3.5% and 11%) at the end of spermiogenesis, when histones are replaced by the protamine galline.     

Interactions between HMG proteins and the core sequence of DNaseI hypersensitive site 2 in the locus control region (LCR) of the human β-like globin gene cluster

HMG proteins are abundant chromosomal non-histone proteins. It has been suggested that the HMG proteins may play an important role in the structure and function of chromatin. In the present study, the binding of HMG proteins (HMG1/2 and HMG14/17) to the core DNA sequence of DNaseI hypersensitive site 2 (HS2core DNA sequence, -10681--10970 bp) in the locus control region (LCR) of the human b-like globin gene cluster has been examined by using both the in vitro nucleosome reconstitution and the gel mobility shift assays. Here we show that HMG1/2 can bind to the naked HS2core DNA sequence, however, HMG14/17 cannot. Using the in vitro nucleosome reconstitution we demonstrate that HMG14/17 can bind to the HS2core DNA sequence which is assembled into nucleosomes with the core histone octamer transferred from chicken erythrocytes. In contrast, HMG1/2 cannot bind to the nucleosomes reconstituted in vitro with the HS2core DNA sequence. These results indicate that the binding patterns between HMG proteins and the HS2core DNA sequence which exists in different states (the naked DNA or the in vitro reconstituted nucleosomal DNA) are quite different. We speculate that HMG proteins might play a critical role in the regulation of the human β-like globin gene's expression.     

High mobility group proteins in ram spermatids

The four major high mobility group proteins HMG 1, 2, 14 and 17, HMG 19B and histone H1(0) were identified in the ram testis by their extraction and solubility characteristics and by their electrophoretic mobilities. HMG 14 and 17 were isolated by chromatography and amino acid analysis revealed that they were similar to their calf thymus analogues. A protein, named 2R and co-extracted with HMG 14, was also purified and analysed. Electrophoretic analyses of the proteins extracted by 0.75 M perchloric acid (PCA) or by 0.35 M NaCl from round and non-round spermatids, separated by centrifugal elutriation, showed that the four major HMG proteins disappear from nuclei in the oldest round spermatids, at the time the nuclear content of protein 2R and histone H1(0) increases in spermatids. Ubiquitin and HMG 19B were present in the round and elongating spermatids, but not in elongated spermatids which contained only protamine. The relation was considered between several protein changes and genetic inactivation and structural reorganization of the spermatid chromatin.     

Interactions between HMG proteins and the core sequence of DNaseI hypersensitive site 2 in the locus control region (LCR) of the human β-like globin gene cluster

HMG proteins are abundant chromosomal non-histone proteins. It has been suggested that the HMG proteins may play an important role in the structure and function of chromatin. In the present study, the binding of HMG proteins (HMG1/2 and HMG14/17) to the core DNA sequence of DNaseI hypersensitive site 2 (HS2core DNA sequence, -10681-10970 bp) in the locus control region (LCR) of the human β-like globin gene cluster has been examined by using both thein vitro nucleosome reconstitution and the gel mobility shift assays. Here we show that HMG1/2 can bind to the naked HS2core DNA sequence, however, HMG14/17 cannot. Using thein vitro nucleosome reconstitution we demonstrate that HMG14/17 can bind to the HS2core DNA sequence which is assembled into nucleosomes with the core histone octamer transferred from chicken erythrocytes. In contrast, HMG1/2 cannot bind to the nucleosomes reconstitutedin vitro with the HS2core DNA sequence. These results indicate that the binding patterns between HMG proteins and the HS2core DNA sequence which exists in different states (the naked DNA or thein vitro reconstituted nucleosomal DNA) are quite different. We speculate that HMG proteins might play a critical role in the regulation of the human β-like globin gene’s expression.     

Studies on protein organization of nucleosomes using cross-linking

When chromosomal proteins in chromatin or in mononucleosomes were extensively cross-linked with an imido ester, the H1-containing nonameric histone complex was revealed. In this complex, histone H1 is connected with the octamer of core histones. The cross-linking of H1 to the octamer is realized preferentially through H2a and H3 histones. Some HMG (high mobility group) proteins located presumably in the linker regions of a nucleosome fiber also take part in the formation of dimers, possibly with the histones of a nucleosomal core. The results suggest mutual interactions between some linker-associated proteins and intranucleosomal histones. Experiments involving extensive cross-linking of proteins in the purified mononucleosome subfractions demonstrated differences in the organization of core histones between complete nucleosomes and nucleosomes lacking H1.Abbreviations HMG proteins high mobility group proteins - DMA dimethyladipimidate dihydrochloride - DMP dimethyl-3,3-dithio-bis-propionimidate dihydrochloride     

A single-column chromatographic system for the analysis and preparation of high mobility group proteins 1 and 2 and other chromosomal proteins using nondenaturing solvents

One-step chromatography on a Mono S column allows the purification of high mobility group (HMG) proteins 1 and 2 under nondenaturing conditions. Chromatography of HMG1 and -2 on Mono S can be achieved with three of the most widely employed extraction techniques for chromosomal proteins, 0.35 M sodium chloride, 0.74 M perchloric acid, and 0.4 N sulfuric acid. In each case HMG1 and -2 are purified away from the other chromosomal proteins, histone H1, and core histones, and are resolved into both their reduced and oxidized forms. Additionally histone H1 and the core histones are fractionated on Mono S, thus the entire complement of chromosomal proteins can be analyzed in a single rapid chromatographic step.     

Purification and cDNA cloning of maize HMGd reveal a novel plant chromosomal HMG-box protein with sequence similarity to HMGa

We have purified the chromosomal high mobility group (HMG) protein HMGd from maize suspension culture cells, determined the N-terminal amino acid (aa) sequence, and isolated the corresponding cDNA. Sequence analysis showed that the cDNA encoded a protein of 126 aa residues with a theoretical mass of 14 104 Da. The protein contains an HMG-box DNA-binding domain and a short acidic C-terminal tail. HMGd is in approx. 65% of its residues identical to maize HMGa, whereas it is only approx. 46% identical to maize HMGcl/2. The differences to the previously reported HMG proteins in aa sequence, in overall charge and in protein size indicate that we have identified a third type of plant chromosomal HMG-box protein belonging to the HMG1 protein family. Immunoblot analysis with a HMGd antiserum reveals that HMGd is expressed in all tissues tested.     

ADP-ribosylation of nonhistone high mobility group proteins in intact cells

The ADP-ribosylation of nonhistone, high mobility group (HMG) proteins in intact cultured cells was investigated. Radioactively labeled adenosine was used as a precursor to detect (ADP-ribose)n on protein. A protein fraction enriched in HMG proteins and histone H1 was separated from RNA and DNA by CsCl density gradient centrifugation, 5% perchloric acid extraction, and CM-Sephadex C-50 column chromatography. Poly- and mono(ADP-ribose) were recovered following alkaline hydrolysis, and 5'-AMP and (2'-(5"-phosphoribosyl)-5'-AMP) were produced by phosphodiesterase treatment, indicating that the protein-bound radioactive material was (ADP-ribose)n. An average chain length of 1.5 to 1.8 was determined. Analysis of proteins by sodium dodecyl sulfate and acetic acid/urea polyacrylamide gel electrophoresis demonstrated that HMG 1, 2, 14, and 17 as well as histone H1 contained (ADP-ribose)n. Treatment of cells with 3-aminobenzamide, an inhibitor of (ADP-ribose)n synthetase, decreased endogenous ADP-ribosylation in both types of chromosomal proteins but that of HMG 14 and 17 was affected more.     

Characterization of high mobility group protein levels during spermatogenesis in the rat

The distribution, quantitation, and synthesis of high mobility group (HMG) proteins during spermatogenesis in the rat have been determined. HMG1, -2, -14, and -17 were isolated from rat testes by Bio-Rex 70 chromatography combined with preparative gel electrophoresis. Amino acid analysis revealed that each rat testis HMG protein was similar to its calf thymus analogue. Tryptic peptide maps of somatic and testis HMG2 showed no differences and, therefore, failed to detect an HMG2 variant. Testis levels of HMG proteins, relative to DNA content, were equivalent to other tissues for HMG1 (13 micrograms/mg of DNA), HMG14 (3 micrograms/mg of DNA), and HMG17 (5 micrograms/mg of DNA). The testis was distinguished in that it contained a substantially higher level of HMG2 than any other rat tissue (32 micrograms/mg of DNA). HMG protein levels were determined from purified or enriched populations of testis cells representing the major stages of spermatogenesis; spermatogonia and early primary spermatocytes, pachytene spermatocytes, early spermatids, and late spermatids; and testicular somatic cells. High levels of HMG2 in the testis were due to pachytene spermatocytes and early spermatids (56 +/- 4 and 47 +/- 6 micrograms/mg of DNA, respectively). Mixtures of spermatogonia and early primary spermatocytes showed lower levels of HMG2 (12 +/- 3 micrograms/mg of DNA) similar to proliferating somatic tissues, whereas late spermatids had no detectable HMG proteins. The somatic cells of the testis, including isolated populations of Sertoli and Leydig cells, showed very low levels of HMG2 (2 micrograms/mg of DNA), similar to those in nonproliferating somatic tissues. HMG proteins were synthesized in spermatogonia and primary spermatocytes, but not in spermatids. Rat testis HMG2 exhibited two bands on acid-urea gels. A "slow" form comigrated with somatic cell HMG2, while the other "fast" band migrated ahead of the somatic form and appeared to be testis-specific. The "fast" form of HMG2 accounted for the large increase of HMG2 levels in rat testes. These results show that the very high level of HMG2 in testis is not associated with proliferative activity as previously hypothesized.