Polyamine induced changes in the ADP-ribosylation of nuclear proteins from rat liver

Purified rat liver nuclei were incubated $\text{in vitro}$ with [³H]NAD. Altered patterns of ADP-ribosylation of nuclear proteins occurred with 1 mM spermidine or spermine with the latter polyamine causing the greater change. Spermine treated nuclei showed a two-fold increase in ADP-ribose incorporation into H1 histones and a decrease in the other histones. Likewise, the incorporation into the more acidic non-histone nuclear proteins was greater with spermine than spermidine. These results suggest that polyamines may exert a regulatory function by altering the pattern of ADP-ribosylation of both histone and non-histone nuclear proteins.     

Acceptors of poly(ADP-ribosylation) in differentiation inducer-treated and untreated Friend erythroleukemia cells

Acceptors of poly(ADP-ribosylation) were identified and compared between inducer-treated and untreated Friend erythroleukemia cells. When permeabilized Friend cells were pulse labeled with 0.6 μM [³²P]NAD for 1 min and labeled proteins analyzed by SDS-polyacrylamide gel electrophoresis, nucleosome core histones were found to be the primary acceptors, with an additional minor radioactive peak at a position corresponding to M_r = 170 000. Friend cells induced to differentiate by DMSO treatment showed a similar distribution of radioactivity, but with a 60% reduction in the overall level of poly(ADP-ribosylation) under identical labeling conditions. When isolated nuclei were pulse labeled with 0.6 μM [³²P]NAD, radioactive peaks were not restricted mainly at the positions of core histones but widely dispersed in the area from 10 to 50 kDa with another peak at 170 kDa. Increase of NAD concentration resulted in the overall shift of peaks to higher molecular weight positions. When pulse-labeled nuclei or permeable cells were chased with 1 mM NAD, radioactive peaks migrated to positions of very high molecular weight (>M_r = 180 000). Remarkable suppression of poly(ADP-ribose) synthesis was observed when DMSO, hexamethylene bisacetamide, butyric acid, or hemin were used as the inducers.     

Unique acceptors for poly(ADP-ribose) in resting,proliferating and DNA-damaged human lymphocytes

Acceptor proteins for poly(adenosine diphosphoribosyl)ation were determined in resting human lymphocytes, in lymphocytes with N-methyl-N′-nitro-N-nitrosoguanidine-induced DNA damage and in lymphocytes stimulated to proliferate by phytohemagglutinin. Kinetic studies showed that the increase in ADP-ribosylation which occurred in response to N-methyl-N′-nitro-N-nitrosoguanidine (MNNG) treatment was greater in magnitude but more transient in duration than that which occurred in phytohemagglutinin-stimulated cells. Gel electrophoretic analyses revealed that MNNG treatment and phytohemagglutinin stimulation both caused an increase in ADP-ribosylation of poly(ADP-ribose) polymerase and core histones. In MNNG-treated cells, an increase in ADP-ribosylation of histone H1 was also observed. In contrast, phytohemagglutinin-stimulated cells showed no increase in ADP-ribosylation of histone H1. In MNNG-treated cells there was also ADP-ribosylation of a protein of molecular weight 62 000, while in phytohemagglutinin-stimulated cells there was a marked increase in ADP-ribosylation of a protein of molecular weight 96000. MNNG treatment of phytohemagglutinin-stimulated cells produced a pattern of ADP-ribosylation that appeared to be due to the combined effects of the individual treatments. 3-Aminobenzamide effectively inhibited ADP-ribosylation under all treatment conditions.     

Peptide mapping of fat cell membrane substrates for cholera toxin-catalyzed ADP-ribosylation

Incubating rat fat cell membranes with [³²P]NAD⁺ and cholera toxin results in ADP-ribosylation of three distinct components with approximate molecular weights of 42 000, 46 000 and 48 000. Partial proteolytic peptide maps of the M_r = 46 000 and 48 0000 toxin-specific substrates generated by elastase, α-chymotypsin, or Staphylococcus aureus V-8 protease were nearly identical, while those of the M_r = 42 000 target lacked several peptides common to both of the larger molecular weight targets. In addition, peptide maps generated from the M_r = 42 000 target displayed a number of peptides which were absent from the maps generated from either the M_r = 46 000 or 48 000 targets. These data suggest that the M_r = 46 000 and 48 000 substrates are closely related proteins, however the relationship between the M_r = 42 000 toxin-specific substrate and the larger peptides remains to be established. The relative patterns of fat cell membrane labelling by cholera toxin in the presence of [³²P]NAD⁺     

Uncoordinate synthesis of histone H1 in cells arrested in the G1 phase

It has been known for several years that DNA replication and histone synthesis occur concomitantly in cultured mammalian cells. Normally all five classes of histones are synthesized coordinately. However, mouse myeloma cells, synchronized by starvation for isoleucine, synthesize increased amounts of histone H1 relative to the four nucleosomal core histones. This unscheduled synthesis of histone H1 is reduced within 1 h after refeeding isoleucine, and is not a normal component of G1. The synthesis of H1 increases coordinately again with other histones during the S phase. The DNA synthesis inhibitors, cytosine arabinoside and hydroxyurea, block all histone synthesis in S-phase cells. The levels of histone H1 mRNA, relative to the other histone mRNAs, is increased in isoeleucine-starved cells and decreases rapidly after refeeding isoleucine. The increased incorporation of histone H1 is at least partially due to the low isoleucine content of histone H1. Starvation of cells for lysine resulted in a decrease in H1 synthesis relative to core histones. Again the ratio was altered on refeeding the amino acid. 3T3 cells starved for serum also incorporated only H1 histones into chromatin. The ratio of different H1 proteins also changed. The synthesis of the H1⁰ protein was predominant in G₀ cells, and reduced in S-phase cells. These data indicate the metabolism of H1 is independent of the other histones when cell growth is arrested.     

The effects of histones H1o,H5 and HMG proteins on cell division of cultured murine erythroleukemia cells

Summary In the present study the effect of histones H1^o and H5, and the nonhistone chromatin proteins HMG 1, 2, 14 and 17 (the high mobility group proteins), as well as the acidic peptide fragments of HMG 1 and 2 and polyglutamate, on cell division and differentation of cultured murine erythroleukemia (Friend) cells has been investigated. It was found that histones H1^o and H5, the acidic peptide fragments of HMG 1 and 2, HMG 14 and 17 and sodium polyglutamate stimulated cell division at a concentration of 10 g/ml. None of the H1^o, H5 or HMG protein preparations induced hemoglobin synthesis, as judged by benzidine staining.     

Adenosine diphosphate ribosylation of chicken-erythrocyte histones H1, H5 and high-mobility-group proteins by purified calf-thymus poly(adenosinediphosphate-ribose) polymerase

Poly(ADP-ribosylation) of histones H1, H5 and non-histone chromosomal high-mobility-group proteins HMG 1, 2, 14 and 17 from chicken erythrocytes by purified calf thymus poly(ADP-ribose) polymerase was studied using acid/urea/Triton gel electrophoresis and autoradiography. With histone H1, besides ADP-ribosylated H1 supporting short chains of polymer, the appearance of H1 'dimer' was observed and this reaction was dependent on NAD concentration and incubation time. In addition, highly modified and/or aggregated species of histone H1 were observed. Histone H5 was slightly ADP-ribosylated at low NAD concentrations. At higher NAD concentrations or after longer incubations the formation of H5 'dimer' and of more modified forms of H5 could be observed. HMG 1 and HMG 2 were found to be ADP-ribosylated, the reaction being dependent on NAD concentration and time. Here again some discrete intermediates appeared. HMG 14 and HMG 17 were only slightly ADP-ribosylated under our experimental conditions. These results indicate that the purified DNA-independent poly(ADP-ribose) polymerase can catalyse the formation of H1 'dimer' as in nuclei and nucleosomes and that H5 and HMG proteins can also be ADP-ribosylated and produce well-defined higher complexes. These modifications of nuclear proteins may provide a means of localized conformational changes of the chromatin structure in vivo.     

Protein phosphatases in developing Dictyostelium discoideum cells

Protein phosphatase activities in developing Dictyostelium discoideum cells were investigated. Substrates were prepared by phosphorylation of histone H2b and kemptide (Leu-Arg-Arg-Ala-Ser-Leu-Gly) using cAMP-dependent protein kinase. Two histone phosphatase activities (M_r 170 000 and 520 000) and one kemptide phosphatase activity (M_r 230 000) were found in the cytosolic cell fraction. Histone phosphatase was also present in the particulate fraction, kemptide phosphatase was not. All phosphatase activities were present throughout development. No differences in protein phosphatase activities were found in prespore and prestalk cells. A heat-stable factor which inhibits the particulate and both soluble histone phosphatase activities was isolated.     

Reduction of histone cytotoxicity by the Alzheimer β-amyloid peptide precursor

In a search for Alzheimer β-amyloid peptide precursor ligands, Potempska et al. (Arch. Biochem. Biophys. (1993) 304, 448) found that histones bind with high affinity and specificity to the secreted precursor. Because exogenous histones can be cytotoxic, we compared the effects of histones on the viability of cells which produce little β-amyloid peptide precursor (U-937) to those on cells that produce twenty times as much precursor (COS-7). Addition of purified histones caused necrosis of U-937 cells (histone H4, LD₅₀=1.5 μM). Extracellular Aβ precursor in the submicromolar range prevented histone-induced U-937 cell necrosis. Cell-surface precursor also reduced histone toxicity: COS-7 cells were less sensitive to the toxic effects of histone H4 (LD₅₀=5.4 μM). COS-7 cells in which the expression of an APP mRNA-directed ribozyme reduced the synthesis of the protein by up to 80% were more sensitive to histone H4 (LD₅₀=3.2 μM) than cells that expressed the vector alone. Histone H4 binds to cell-associated Aβ precursor. Cells expressing the Aβ precursor-directed ribozyme bound less ¹²⁵I-labeled histone H4 than those expressing the vector alone. In the limited extracellular space of tissues in vivo, both secreted and cell-surface Aβ precursor protein may play significant roles in trapping chromatin or histones and removing them from the extracellular milieu.     

Heterogeneity of the histone-containing chromatin in sea cucumber spermatozoa : Distribution of the basic protein Φ0 and absence of non-histone proteins

Nuclei of spermatozoa of the sea cucumber Holothuria tubulosa contain the five somatic-type histones plus a sperm-specific histone H1 and a unique basic protein ₀, which is related to H1 in amino acid composition. No proteins of the High Mobility Group (HMG) type have been detected. The structure of this chromatin has been probed by nuclease digestion. Its behaviour is anomalous, since two distinct fractions of chromatin are recovered from these spermatozoa, which differ either in the presence or absence of the sperm-specific proteins H1 and ₀. This heterogeneous distribution is not found in conventional materials, such as calf thymus or chicken erythrocytes. Proteins H1 and ₀ are not uniformly distributed and may be localized in special regions of chromatin. Fragments containing long stretches of nucleosomes lacking both proteins can be recovered. At the same time, the chromatin fractions which contain these two proteins are shown to be less soluble. When an extensive digestion of chromatin is carried out yielding only nucleosomes and small oligomers, the H1 and ₀ proteins redistribute themselves on chromatin, the two proteins acting in a cooperative fashion in this process. Cross-linking experiments carried out in whole cells indicate a proximity of ₀ and H1, whereas no crosslinks have been detected between ₀ and any of the four nucleosomal histones. The ₀ protein may thus play a role similar to histone H1 and be only loosely associated with nucleosomal histones, but contribute to the structuration of chromatin during spermiogenesis.     

Acetylation of histones during spermatogenesis in the rat

Acetate was actively incorporated into rat testis histones when testis cells were prepared by the trypsinization technique in the presence of [³H]acetate. The acetylation was enhanced by 10 mm sodium butyrate. Although histones H3 and H4 were the only histones which incorporated high levels of acetate, the testis-specific histones TH2B and TH3 also appeared to incorporate acetate. This was shown by electrophoresis of the histones on polyacrylamide gels containing Triton X-100. Results, obtained from analysis of histones by two-dimensional gel electrophoresis, confirmed a recent report (P. K. Trostle-Weige, M. L. Meistrich, W. A. Brock, K. Nishioka, and J. W. Bremer, (1982) J. Biol. Chem.257, 5560–5567) that TH2A was a testis-specific histone. The results also confirmed the H2A nature of a testis-enriched histone band, previously designated X2. When histones from populations of cells enriched in specific testis cell types, representing various stages of spermatogenesis, were examined, the patterns of acetylation varied dramatically. Very high levels of acetate were incorporated into multiacetylated species of histone H4 from a population of cells enriched in transition stage spermatids (steps 9–12) compared to the levels of acetate incorporated into H4 from round spermatids (steps 1–8) and earlier stages of spermatogenesis, where acetate was incorporated primarily into the monoacetylated species of H4. Thus, a striking correlation exists between the time of hyperacetylation of histone H4 and the time of removal of histones for their replacement by the basic spermatidal transition proteins designated TP, TP2, and TP4. Hyperacetylation of histone H4 may facilitate the removal of the entire histone complement during the protein transition. In any case, it must be an obligatory step in the dramatic process.     

Acetylation of histones of rat testis.

When [1-¹⁴C]acetate was injected into rats intratesticularly in the presence of cycloheximide to inhibit protein synthesis, the label was incorporated into histone fractions F2a1 and F3 and into non-histone chromosomal proteins of each of the following stages of spermatogenesis: spermatogonia-preleptotene spermatocytes, leptotene-zygotene-pachytene-diplotene primary spermatocytes, and spermatids. Acetylation of histones was particularly active in the spermatid stages. There was no significant incorporation of acetate into the lysine-rich histone fractions F1 and X₁.In early periods of in vivo incorporation of [³H]amino acids into histones the acetylated histone F2a1 fractions had higher specific activities than the main band of F2a1, but with the passage of time the label moved into the principal band to the extent that specific activities in the acetylated and principal bands were approximately equal at 6 days. However, at 24–36 days the specific activities were again higher in the acetylated bands than in the principal band of F2a1. These data support the conclusions of Candido, Louie, and Dixon, from experiments with trout testis, that acetylation of histone F2a1 may be important in the process of combination of this protein with DNA in chromatin at the spermatogonia-primary spermatocyte stage and also in the subsequent removal of this histone for replacement by protamines at the spermatid stage.[³H]Amino acids were incorporated into histone fractions X₁ and F1 at approximately equal rates, and there was no evidence that one of these fractions was a precursor of the other.Chromatin of the seminiferous epithelial cells of rat testis has a firmly bound acetylase which catalyzes the in vitro acetylation of histones F3 and F2a1 by acetyl CoA.     

Phosphorylation of high-mobility-group chromatin proteins by protein kinase C from rat brain

Chromosomal high-mobility-group (HMG) proteins have been examined as substrates for calcium/phospholipid-dependent protein kinase C. Protein kinase C from rat brain phosphorylated efficiently both HMG 14 and HMG 17 derived from calf thymus and the reactions were calcium/phospholipid-dependent. About 1 mol of ³²P was incorporated per mol of HMG 14 and HMG 17. Phosphopeptide mapping suggested that the same major site was phosphorylated in both proteins at serine. The apparent K_m values for HMG 14 and HMG 17 were about 5 μM. HMG 14, HMG 17 and the five histone H1 subtypes prepared from rat thymus, liver and spleen were phosphorylated by the kinase. HMG 14 and HMG 17 from transformed human lymphoblasts (Wi-L2) were also phosphorylated in a calcium/phospholipid-dependent manner. HMG 1 and HMG 2 from the tissues examined were found to be poor substrates for the kinase.     

Fractionation and characterization of rapidly phosphorylated nuclear proteins in salivary gland cells of Chironomus tentans

Rapidly phosphorylated nuclear proteins were investigated in explanted salivary gland cells of Chironomus tentans after labeling with ³²P_i. After sonication nuclei were fractionated by centrifugation at 18,000 g into sedimentable (80% of ³²P) and not sedimentable (supernatant) material. About 90% of ³²P in the supernatant fraction was sedimentable at 100,000 g (disperse chromatin). The disperse chromatin contained 20%–40% of the total nuclear DNA but only 5%–20% of ³²P. The ³²P-labeled phosphoproteins in the material pelleted at 20,000 g were further fractionated by differential solubility in lysis buffer. Electrophoretic analyses on SDS polyacrylamide gels resolved the ³²P-labeled nuclear proteins into 12 major bands in the M_r range of 12,000–120,000. The incorporation of ³²P into most bands reached a steady-state within 5–10 min of incubation with ³²P_i and was not measurably influenced by cycloheximide, an inhibitor of protein synthesis. The phosphate groups are linked to polypeptide chains by bonds vulnerable to pronase and alkaline phosphatase. All major bands in the pelleted chromatin were also present in the disperse chromatin except for an M_r 95,000 phosphoprotein. Two of the fastest moving ³²P-bands comigrated with the core histones H2A and H4. Both possessed a high pI value and were insoluble in 0.35 M NaCl. The H2A-like protein was partially soluble in lysis buffer while the H4-like one was not. The two fast moving ³²P-labeled bands with rapidly turned over phosphates may be fractions or variants of the core histones H2A and H4.     

ADP-ribosylation of chromosomal proteins and mouse mammary tumor virus gene expression. Glucocorticoids rapidly decrease endogenous ADP-ribosylation of nonhistone high mobility group 14 and 17 proteins

The relationship between endogenous ADP-ribosylation of chromosomal proteins and glucocorticoid-regulated mouse mammary tumor virus gene expression was investigated in cultured mouse mammary tumor cells. It was observed that glucocorticoids quickly decreased endogenous (ADP-ribose)n on the nonhistone high mobility group (HMG) 14 and 17 proteins. The half-time for this loss was 8 and 17 min, respectively, for the two proteins. (ADP-ribose)n on HMG 1 and 2 and on histone H1 was less susceptible to hydrolysis during glucocorticoid treatment. The rapid loss of (ADP-ribose)n from HMG 14 and 17 occurred in the same time frame as the induction of mouse mammary tumor virus RNA synthesis by glucocorticoids in these cells (Young, H. A., Shih, T. Y., Scolnick, E. M., and Parks, W. P. (1977) J. Virol. 21, 139-149). 3-Amino-benzamide, a specific inhibitor of (ADP-ribose)n synthetase, increased mouse mammary tumor virus RNA levels with an accompanying decrease in endogenous ADP-ribosylation of HMG 14 and 17. These results show that a decrease in endogenous ADP-ribosylation of HMG 14 and 17 is a consequence of glucocorticoid action and suggest that loss of (ADP-ribose)n from these proteins may be an important event in mouse mammary tumor virus gene expression.     

Evidence from triton X-100 polyacrylamide gel electrophoresis that histone f2a2, not f2b, is phosphorylated in Chinese hamster cells

Chinese hamster cells (line CHO) were labeled in suspension culture with ³H-lysine and ³²PH₃PO₄. Preparative polyacrylamide gel electrophoresis of histone fractions from these cells was performed in the presence of 8 $\text{M}$ urea, 6 mM Triton X-100, and 0.9 N acetic acid. This method separates histones f2a2 and f2b by a Large distance, thus making it possible to resolve the controversy concerning which histone -- f2b or f2a2 -- is phosphorylated. It is shown that the two most highly phosphorylated histones in interphase CHO cells are f1 and f2a2. Histones f2b and f3 are shown to contain no significant incorporation of ³²PO₄ in interphase cells, while histone f2a1 contains a small but detectable amount of incorporated ³²PO₄. Binding of the nonionic detergent Triton X-100 to hydrophobic centers appears to be greatest for histones f2a2 and f3, thus significantly retarding the mobility of these two histones during electrophoresis.     

In vitro ADP-ribosylation of chromosomal proteins of the brain of developing rats

In vitro ADP-ribosylation of chromosomal protein and its modulation by spermine, 3-aminobenzamide (3-AB) and benzamide were studied by incubating the nuclei of cerebral hemisphere of 3-, 14- and 30-day old rats with ³²P-NAD⁺. Histones get ADP-ribosylated more than the non-histone chromosomal (NHC) protein. H1 is the major target for ADP-ribosylation. Among the nucleosomal histones, H2B is ADP-ribosylated most. The other core histones also get ADP-ribosylated to a lesser extent. ADP-ribosylation of both histones and NHC proteins decreases during development. Spermine stimulates, whereas 3-AB and benzamide inhibit, ³²P-ADP-ribose incorporation into histones and NHC proteins. These effects decrease with development. Mild digestion of chromatin by micrococcal nuclease (MNase), EcoRI, and AluI prior to ADP-ribosylation stimulates incorporation of ³²P-ADP-ribose. The degree of stimulation decreases as development proceeds. Such alterations indicate progressive condensation of chromatin with development.