Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound

---

Query: EC:3.1.31.1 (micrococcal nuclease)
2,818 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The assembly of hybrid core particles onto long chicken DNA with histone H2B in the chicken histone octamer replaced with either wheat histone H2B(2) or sea urchin sperm histone H2B(1) or H2B(2) is described. All these histone H2B variants have N-terminal extensions of between 18 and 20 amino acids, although only those from sea urchin sperm have S(T)PXX motifs present. Whereas chicken histone octamers protected 167 base pairs (bp) (representing two full turns) of DNA against micrococcal nuclease digestion (Lindsey, G. G., Orgeig, S., Thompson, P., Davies, N., and Maeder, D. L. (1991) J. Mol. Biol. 218, 805-813), all the hybrid histone octamers protected an additional 17-bp DNA against nuclease digestion. This protection was more marked in the case of hybrid octamers containing sea urchin sperm histone H2B variants and similar to that described previously (Lindsey, G. G., Orgeig, S., Thompson, P., Davies, N., and Maeder, D. L. (1991) J. Mol. Biol. 218, 805-813) for hybrid histone octamers containing wheat histone H2A variants all of which also have S(T)PXX motifs present. Continued micrococcal nuclease digestion reduced the length of DNA associated with the core particle via 172-, 162-, and 152-bp intermediates until the 146-bp core particle was obtained. These DNA lengths were approximately 5 bp or half a helical turn longer than those reported previously for stripped chicken chromatin and for core particles containing histone octamers reconstituted using "normal" length histone H2B variants. This protection pattern was also found in stripped sea urchin sperm chromatin, demonstrating that the assembly/digestion methodology reflects the in vivo situation. The interaction between the N-terminal histone H2B extension and DNA of the "linker" region was confirmed by demonstrating that stripped sea urchin sperm chromatin precipitated between 120 and 500 mM NaCl in a manner analogous to unstripped chromatin whereas stripped chicken chromatin did not. Tryptic digestion to remove all the histone tails abolished this precipitation as well as the protection of DNA outside of the 167-bp core particle against nuclease digestion.
...
PMID:S(T)PXX motifs promote the interaction between the extended N-terminal tails of histone H2B with "linker" DNA. 163 9

Histone ADP-ribosylation was studied using two-dimensional gel electrophoresis after cleavage of the nuclear DNA with nucleases. Modified histones carrying different numbers of ADP-ribose groups form a ladder of bands above each variant histone. Cellular lysates containing unfragmented DNA mainly synthesize mono(ADP-ribosylated) histones. Cleavage of the DNA with either DNase I or micrococcal nuclease to fragments of an average size of 10-20 kilobases (kb) dramatically induces the formation of poly(ADP-ribosylated) species of histones in nuclei. As the number of DNA strand breaks produced by either DNase I or micrococcal nuclease increases and a great number of DNA cuts is introduced (fragments of 0.4-0.2 kb), the size of the poly(ADP-ribose) chains on the histones decreases. Finally, in the presence of 10 mM cAMP as an inhibitor of poly(ADP-ribose) glycohydrolase, human lymphoid nuclei synthesize hyper(ADP-ribosylated) histone H2B with at least 40 ADP-ribose groups attached to it. Lateral ladders emanating at precise points of the linear ladder on hypermodified H2B can arise from branching of poly(ADP-ribose) or from multiple monomodifications of glutamic (or aspartic) acid residues. Branching or de novo monomodifications occur after a precise number of ADP-ribose groups have been added to a histone molecule. Poly(ADP-ribosylated) histones thus appear to be intermediates in nuclear processes involving DNA strand breaks.
...
PMID:DNA strand breaks alter histone ADP-ribosylation. 272 32

A mouse monoclonal IgM antibody against the core histone H2B has been shown, by indirect immunofluorescence, to stain metaphase chromosomes from a variety of cultured cell types. Experiments carried out with human HeLa cells showed that the intensity of staining varied along the length of chromosome arms giving in some cases a rudimentary banded staining pattern. Considerable variation in staining intensity was noted between individual chromosomes and between different metaphase spreads. It was noted that chromosomes having a more swollen appearance stained more intensely than those with a more compact structure, which were often unstained. Preincubation of unfixed metaphase chromosomes in buffered salt solutions virtually eliminated the cell to cell and chromosome to chromosome variation in staining, even when no visible effect on chromosome morphology was caused by such treatment. It is concluded that the determinant recognised by antibody HBC-7 is ubiquitous but is inaccessible in some chromosomes or chromosome regions. Digestion of purified chromatin (primarily interphase) with DNAase 1 or micrococcal nuclease resulted in a several-fold increase in the binding of antibody HBC-7 measured by solid-phase radioimmunoassay. This increase was abolished by subsequent treatment with trypsin, which suggests that the antigenic determinant recognised by antibody HBC-7 lies in the trypsin-sensitive N-terminal region of nucleosomal H2B. As the cationic N-terminal regions of the core histones are involved in DNA binding, it is likely that the accessibility of the determinant recognised by antibody HBC-7 is influenced by the relationship between the core histones and their associated DNA.
...
PMID:Immunofluorescent staining of human metaphase chromosomes with monoclonal antibody to histone H2B. 676 Oct 99

Comparison has been made between sea urchin and starfish sperm chromatin. The only protein by which chromatins from these sources differ significantly is histone H2B. Sea urchin sperm H2B is known to contain an elongated N-terminal region enriched in Arg. Analysis of the micrococcal nuclease digests of sea urchin and starfish nuclei in one- and two-dimensional electrophoresis has shown that sperm chromatin of both animals consists of repeated units similar in general features to those of rat thymus or liver. However, DNA repeat length in chromatin of sea urchin sperm (237 bp) is higher than that of starfish sperm (224 bp), while the core DNA length does not differ and is the same as in the chromatin of rat liver or thymus. A suggestion has been made that the N-terminal region of histone H2B is associated with the linker DNA and is responsible for the increased length of sea urchin linker DNA.
...
PMID:Nucleosomal structure of sea urchin and starfish sperm chromatin. Histone H2B is possibly involved in determining the length of linker DNA. 722 Mar 45

The product of the RAD6 (UBC2) gene of Saccharomyces cerevisiae is a ubiquitin-conjugating enzyme (Rad6) which is implicated in DNA repair, induced mutagenesis, retrotransposition, sporulation and the degradation of proteins with destabilizing N-terminal amino acid residues. Deletion of the 23-residue acidic C-terminus of Rad6 impairs sporulation and N-end rule protein degradation in vivo but does not affect other functions such as DNA repair and induced mutagenesis. We have investigated the role of the C-terminus of Rad6 in in vitro interactions with various substrates and with a putative ubiquitin-protein ligase, E3-R. The removal of the Rad6 C-terminus had significant different effects on enzyme activity for individual substrates. Although the 23-residue truncated Rad6-149 protein had markedly impaired activity for histone H2B and micrococcal nuclease, the activity for cytochrome c was the same as that of the intact Rad6 protein. Similarly, truncation of Rad6 had no effect on its activity for several poor substrates, namely, beta-casein, beta-lactoglobulin and oxidized RNase. E3-R stimulated the activities of both Rad6 and Rad6-149 for the latter three substrates to similar degrees. E3-R appears to act by enhancing the low intrinsic affinity of Rad6 and Rad6-149 for these substrates. Thus Rad6 can act in three different modes in vitro depending on the substrate, namely unassisted C-terminus-dependent, unassisted C-terminus-independent and E3-R-assisted C-terminus-independent modes. We also examined the results of removing the C-terminal acidic region of Cdc34 (Ubc3), a ubiquitin-conjugating enzyme closely related to Rad6. Truncation of Cdc34 like that of Rad6 had no effect on activity for beta-casein, beta-lactoglobulin or oxidized RNase in the presence or absence of E3-R.
...
PMID:Role of the C-terminus of Saccharomyces cerevisiae ubiquitin-conjugating enzyme (Rad6) in substrate and ubiquitin-protein-ligase (E3-R) interactions. 816 12

Human sperm, unlike the sperm of other mammals, contain replacement histones with unknown biological functions. Here, we report the identification of the novel human gene coding for a testis/sperm-specific histone H2B (hTSH2B). This variant histone is 85% homologous to somatic H2B and has over 93% homology with the testis H2B of rodents. Using genomic PCR, two genetic alleles of hTSH2B were found in the human population. The hTSH2B gene is transcribed exclusively in testis, and the corresponding protein is also present in mature sperm. We expressed recombinant hTSH2B and identified this protein with a particular H2B subtype expressed in vivo. The subnuclear distribution of H2B variants in sperm was determined using biochemical fractionation and immunoblotting. The H2B variant associated with telomere-binding activity () was solubilized by Triton X-100 or micrococcal nuclease extraction, whereas hTSH2B was relatively tightly bound in nuclei. Immunofluorescence showed that hTSH2B was concentrated in spots located at the basal nuclear area of a subpopulation (20% of cells) of mature sperm. This fact may be of particular importance, because the hTSH2B "positive" and "negative" sperm cells may undergo significantly different decondensation processes following fertilization.
...
PMID:Human testis/sperm-specific histone H2B (hTSH2B). Molecular cloning and characterization. 1221 18

A histone heterodimer, designated as p28, which contains an Nepsilon(gamma-glutamyl)lysine cross-link between Gln9 of histone H2B and Lys5 or Lys12 of histone H4, is present in starfish (Asterina pectinifera) sperm. Treatment of sperm nuclei with micrococcal nuclease produced soluble chromatin, which was size-fractionated by sucrose-gradient centrifugation to give p28-containing oligonucleosome and p28-free mononucleosome fractions, indicating that the cross-link is internucleosomal. When sperm nuclei were incubated with monodansylcadaverine, a fluorescent amine, in the presence or absence of Ca(2+), histone H2B was modified only in the presence of Ca(2+). Gln9, in the N-terminal region, was modified, but the other Gln residues located in the internal region were not, suggesting that the modification takes place on the surface of the nucleosome core by the in situ action of a Ca(2+)-dependent nuclear transglutaminase. Treatment of sperm with the egg jelly, which activates Ca(2+) influx to induce the acrosome reaction, resulted in a significant elevation of the p28 content in the nucleus. This is the first demonstration of an in vivo activation of transglutaminase leading to the formation of a cross-link in intracellular proteins.
...
PMID:In vivo cross-linking of nucleosomal histones catalyzed by nuclear transglutaminase in starfish sperm and its induction by egg jelly triggering the acrosome reaction. 1295 Feb 58

---