METHODS FOR THE PURIFICATION OF THYMUS NUCLEI AND THEIR APPLICATION TO STUDIES OF NUCLEAR PROTEIN SYNTHESIS

Anticancer potential of the histone deacetylase inhibitor-like effects of flavones, a subclass of polyphenolic compounds: a review

Cancer is characterized by the uncontrolled division of cells, followed by their invasion to other tissues. These kinds of cellular abnormalities arise as a result of the accumulation of genetic mutations or epigenetic alterations. Targeting genetic mutations by drugs is a conventional treatment approach. Nowadays, the development and use of epigenetic drugs are burgeoning, owing to the advancements in epigenetic research. The therapeutic intervention of cancer development by histone deacetylase inhibitors (HDACIs) holds promise for helping to control the disease, but their nonspecific functions impose certain side effects. Therefore, the search for more HDACIs becomes essential. Plentiful literature on the versatility of dietary components including flavones, a class of the flavonoid group, has already established these compounds to be better anticancer agents. The present review focuses on the significance of flavones with regard to their HDACI-mimicking effects as suggested by the recent evidences. The review also proposes an in-depth screening of flavones in future studies, in the hope that flavones may provide a better alternative to synthetic HDACIs.

HAT3-mediated acetylation of PCNA precedes PCNA monoubiquitination following exposure to UV radiation in Leishmania donovani

Histone modifications impact various processes. In examining histone acetyltranferase HAT3 of Leishmania donovani, we find elimination of HAT3 causes decreased cell viability due to defects in histone deposition, and aberrant cell cycle progression pattern. HAT3 associates with proliferating cell nuclear antigen (PCNA), helping load PCNA onto chromatin in proliferating cells. HAT3-nulls show heightened sensitivity to UV radiation. Following UV exposure, PCNA cycles off/on chromatin only in cells expressing HAT3. Inhibition of the ubiquitin-proteasome pathway prior to UV exposure allows accumulation of chromatin-bound PCNA, and reveals that HAT3-nulls are deficient in PCNA monoubiquitination as well as polyubiquitination. While poor monoubiquitination of PCNA may adversely affect translesion DNA synthesis-based repair processes, polyubiquitination deficiencies may result in continued retention of chromatin-bound PCNA, leading to genomic instability. On suppressing the proteasome pathway we also find that HAT3 mediates PCNA acetylation in response to UV. HAT3-mediated PCNA acetylation may serve as a flag for PCNA ubiquitination, thus aiding DNA repair. While PCNA acetylation has previously been linked to its degradation following UV exposure, this is the first report linking a HAT-mediated PCNA acetylation to PCNA monoubiquitination. These findings add a new dimension to our knowledge of the mechanisms regulating PCNA ubiquitination post-UV exposure in eukaryotes.

Synthesis of adenosine triphosphate in isolated nuclei and intact cells

1. It has previously been demonstrated that nuclei isolated from normal and neoplastic lymphoid cells are capable of oxygen-dependent ATP synthesis. In this paper it is shown that also the corresponding intact cells can synthesize ATP under those conditions in which nuclei can synthesize ATP. 2. In nuclei isolated from liver, kidney, rhabdomyosarcoma and osteosarcoma, oxygen-dependent ATP synthesis could not be demonstrated. The cells isolated from these tissues or tumours could not synthesize ATP either. The alternatives that such nuclei lost their ability for oxidative phosphorylation during the isolation procedure or that the process does not occur in these nuclei were explored. 3. Janus Green B, a vital stain for mitochondria, was used as a differential inhibitor of mitochondrial and nuclear ATP synthesis in intact cells. 4. Oxidative phosphorylation in mitochondria isolated from cells that had been incubated with various concentrations of Janus Green B (1-10mum) was seriously uncoupled, whereas at these concentrations oxygen-dependent ATP synthesis in isolated nuclei and in isolated cells were only inhibited to a small extent. 5. The results suggest that oxygen-dependent ATP synthesis in isolated cells measured under ;nuclear' conditions and in the presence of Janus Green B and Ca(2+) is mainly due to nuclear oxygen-dependent ATP synthesis. The stimulation of cellular ATP synthesis by glucose was completely inhibited by Janus Green B. 6. It is tentatively concluded that the stimulation of ATP synthesis in isolated cells by glucose, which is not found in isolated nuclei, represents mitochondrial ATP synthesis, and nuclear and mitochondrial ATP synthesis can then be studied differentially in the intact cell. The possibility is considered that oxygen-dependent nuclear ATP synthesis is not a general property of cell nuclei.

Isolation of cell nuclei using inert macromolecules to mimic the crowded cytoplasm

Cell nuclei are commonly isolated and studied in media which include millimolar concentrations of cations, which conserve the nuclear volume by screening the negative charges on chromatin and maintaining its compaction. However, two factors question if these ionic conditions correctly reproduce the environment of nuclei in vivo: the small-scale motion and conformation of chromatin in vivo are not reproduced in isolated nuclei, and experiments and theory suggest that small ions in the cytoplasm are not free in the soluble phase but are predominantly bound to macromolecules. We studied the possible role in maintaining the structure and functions of nuclei in vivo of a further but frequently overlooked property of the cytoplasm, the crowding or osmotic effects caused by diffusible macromolecules whose concentration, measured in several studies, is in the range of 130 mg/ml. Nuclei which conserved their volume in the cell and their ultrastructure seen by electron microscopy were released from K562 cells in media containing the inert polymer 70 kDa Ficoll (50% w/v) or 70 kDa dextran (35% w/v) to replace the diffusible cytoplasmic molecules which were dispersed on cell lysis with digitonin, with 100 microM K-Hepes buffer as the only source of ions. Immunofluorescence labelling and experiments using cells expressing GFP-fusion proteins showed that internal compartments (nucleoli, PML and coiled bodies, foci of RNA polymerase II) were conserved in these nuclei, and nascent RNA transcripts could be elongated. Our observations are consistent with the hypothesis that crowding by diffusible cytoplasmic macromolecules is a crucial but overlooked factor which supports the nucleus in vivo by equilibrating the opposing osmotic pressure cause by the high concentration of macromolecules in the nucleus, and suggest that crowded media provide more physiological conditions to study nuclear structure and functions. They may also help to resolve the long-standing paradox that the small-scale motion and irregular conformation of chromatin seen in vivo are not reproduced in nuclei isolated in conventional ionic media.

Thrombopoietin Upregulates the Promoter Conformation of p53 in a Proliferation-Independent Manner Coincident With a Decreased Expression of Bax: Potential Mechanisms for Survival Enhancing Effects

Thrombopoietin (Tpo) has proliferative and maturational effects on immature and more committed cells, respectively. We previously reported a role for Tpo as a survival factor in the factor-dependent human cell line M07e by demonstrating that Tpo suppresses apoptosis in the absence of induced proliferation. Wild-type p53 is a tumor suppressor gene that can play a vital role in mediating growth factor withdrawal-induced apoptosis in factor-dependent hematopoietic cells. Wild-type p53 can switch from a suppressor conformation, with an antiproliferative, pro-apoptotic phenotype, to a promoter conformation that has a diminished ability to mediate cell cycle arrest and apoptosis. In an effort to elucidate the mechanisms through which Tpo suppresses apoptosis, we investigated the effects of Tpo treatment on p53-mediated apoptosis in M07e cells. Tpo upregulated the expression of the promoter conformation of p53 in M07e cells coincident with a downregulation of Bax and Mdm2 protein levels. Protein levels of Bcl-2 and Bcl-xL did not significantly vary as a function of growth-factor stimulation. Conversely, the levels of suppressor conformation p53 were maximal when M07e was in a growth arrested state and decreased during factor stimulation. Furthermore, Tpo treatment induced an extranuclear buildup and greatly weakened the DNA binding capacity of p53. p53-specific antisense oligonucleotide treatment recapitulated the effects of Tpo treatment on the levels of Bax, Mdm-2, and Bcl-2. These results suggest that Tpo is suppressing growth factor withdrawal induced-apoptosis, at least in part, by downregulating the expression of pro-apoptotic Bax protein levels, through modulating the conformation of p53, which results in a functional inactivation of its pro-apoptotic abilities.

Thrombopoietin Upregulates the Promoter Conformation of p53 in a Proliferation-Independent Manner Coincident With a Decreased Expression of Bax: Potential Mechanisms for Survival Enhancing Effects

Thrombopoietin (Tpo) has proliferative and maturational effects on immature and more committed cells, respectively. We previously reported a role for Tpo as a survival factor in the factor-dependent human cell line M07e by demonstrating that Tpo suppresses apoptosis in the absence of induced proliferation. Wild-type p53 is a tumor suppressor gene that can play a vital role in mediating growth factor withdrawal-induced apoptosis in factor-dependent hematopoietic cells. Wild-type p53 can switch from a suppressor conformation, with an antiproliferative, pro-apoptotic phenotype, to a promoter conformation that has a diminished ability to mediate cell cycle arrest and apoptosis. In an effort to elucidate the mechanisms through which Tpo suppresses apoptosis, we investigated the effects of Tpo treatment on p53-mediated apoptosis in M07e cells. Tpo upregulated the expression of the promoter conformation of p53 in M07e cells coincident with a downregulation of Bax and Mdm2 protein levels. Protein levels of Bcl-2 and Bcl-xL did not significantly vary as a function of growth-factor stimulation. Conversely, the levels of suppressor conformation p53 were maximal when M07e was in a growth arrested state and decreased during factor stimulation. Furthermore, Tpo treatment induced an extranuclear buildup and greatly weakened the DNA binding capacity of p53. p53-specific antisense oligonucleotide treatment recapitulated the effects of Tpo treatment on the levels of Bax, Mdm-2, and Bcl-2. These results suggest that Tpo is suppressing growth factor withdrawal induced-apoptosis, at least in part, by downregulating the expression of pro-apoptotic Bax protein levels, through modulating the conformation of p53, which results in a functional inactivation of its pro-apoptotic abilities.

METABOLIC AND CHEMICAL PROPERTIES OF BASIC PROTEINS ISOLATED FROM NUCLEI OF RAT LIVER AND THYMUS GLAND

1. The effects of alkylating agents and disulphides on the thiol-containing proteins of nuclei from rat thymus and liver were studied. Three protein fractions were examined: histones extracted with 50mm- and 250mm-hydrochloric acid and the residual protein. None of the reagents selectively reacted with any one of the protein fractions. 2. Amino acid uptake in vitro into the histones of nuclei from rat thymus was analysed by preparative electrophoresis of the proteins extracted with 50mm- and 250mm-hydrochloric acid. After 1hr. at 37 degrees the greater incorporation was into the proteins extracted with 50mm-hydrochloric acid. 3. Preparative electrophoresis was used to study the relative thiol contents of the proteins of the 50mm-hydrochloric acid extract from thymus nuclei by labelling the histones in vitro with (14)C-labelled N-ethylmaleimide. 4. The capacity of the proteins extracted from rat thymus with 50mm- and 250mm-hydrochloric acid, and of the components from these extracts separated by preparative electrophoresis, to combine with DNA and to depress DNA-dependent RNA synthesis was studied. The histones extracted with 50mm-hydrochloric acid were more lysine-rich than those extracted with 250mm-hydrochloric acid. Wide variations were found in the abilities of the separated components to depress RNA synthesis.

Amelioration of murine lupus nephritis by dimethylsulfoxide

Dimethylsulfoxide was given to NZB/W F1 female mice from age 10 weeks to see if proteinuria and glomerular injury could be reduced. Twenty mice were randomly assigned to saline or DMSO treatment groups and the following studies were done: urine protein determination, serum concentrations of creatinine, IgG, C3, and albumin; and ANA titers. Kidney tissue were studied by light, immunofluorescent and electron microscopy. DMSO-treated mice had significant reductions in protein excretion at 5 and 6.5 months of age; in urine protein/creatinine ratio at 6.5, 7, and; 7.5 months; in serum C3 at 7.5 months; and in serum creatinine concentration. There were no significant differences among serum IgG, nor among the ANA titers. Histopathologic studies revealed nearly normal kidneys in 5/6 DMSO-treated mice whereas 4/8 controls had severe mixed membranous and membranoproliferative glomerulonephritis. Ultrastructural studies revealed mesangial, subendothelial, and subepithelial deposits and membranous transformation of the glomerular capillary wall. DMSO therefore appears capable of ameliorating glomerular injury in NZB/W F1 mice.

A comparison of lipids from liver and hepatoma subcellular membranes

Subcellular fractions of nuclei, mitochondria, endoplasmic reticulum, plasma membrane and cytosol were prepared from liver and hepatoma 7288CTC. Marker enzyme activities, biochemical compositions and electron microscopy were used to establish purity. Hepatoma NADH: cytochrome C reductase and 5'-nucleotidase exhibited abnormal subcellular distributions. The lipids from the subcellular fractions were examined in detail. Mitochondria and plasma membranes were characterized by elevated percentages of diphosphatidylglycerol and sphingomyelin, respectively, in both tissues. All hepatoma subcellular fractions contained dramatically elevated levels of sphingomyelin and cholesterol, two components that form preferential strong complexes in vitro. The fatty acid composition of hepatoma sphingomyelin differed markedly from liver and, unlike liver, did not exhibit organelle specific compositions. Some hepatoma lipid classes contained reduced percentages of palmitate while others contained higher levels. Hepatoma phosphatidylcholine and phosphatidylethanolamine from organelles contained lower percentages of long chain polyunsaturated fatty acids than liver. Generally, unique fatty acid profiles exhibited by individual phospholipid classes of liver subcellular fractions were absent or much reduced in the hepatoma. The ratios of oleate to vaccenate were near one for most of the phospholipid classes of most liver fractions, but all hepatoma classes, with few exceptions, contained a much higher percentage of oleate in all subcellular fractions. The hypothesis is proposed that the origin of some acyl moieties for the biosynthesis of various hepatoma lipid classes differs from liver sources. The possible changes in acyl pools, sources and compartments for complex lipid biosynthesis could result in change in the quantities of molecular species that could contribute to the abnormal properties of the hepatoma membranes.

Low-speed purification of human placental nuclei

A simple method for the purification of human placental nuclei is described. Nuclei were isolated by homogenizing tissue in standard saline citrate solution in the presence of zinc chloride to stabilize the nuclear membranes, NP40 as non-ionic detergent and sodium bisulphite for inhibition of proteolytic activity. Nuclei purification was achieved by low-speed centrifugation through a discontinuous sucrose gradient. The purified nuclei were evaluated by morphological criteria using phase contrast and electron microscopy. The extent of contamination by cytoplasmic debris was estimated by Papanicolaou's staining technique. Biochemical criteria include measurements of alkaline phosphatase activity as a plasma membrane enzyme marker and DNA-dependent RNA polymerase activity for the functional integrity of nuclear components. Transcriptionally active nuclei were obtained but the yield of nuclei was low; however, this low yield is compensated by the high degree of purity, the simplicity of the method and the functional and morphological integrity of the purified nuclei.

Alteration in the nucleosome and chromatin structures upon interaction with platinum coordination complexes

The interaction of various platinum coordination complexes with nucleosomes and chromatin has been investigated by ultraviolet absorption spectrophotometry, circular and electric linear dichroism, and thermal denaturation, at low binding ratios (r less than 0.1-0.2). The general trend of the changes in these physicochemical properties is similar to that observed for the DNA-platinum complexes, which indicates that the same binding sites are involved in the platinum interaction with DNA and with its nucleoprotein complex. The cis-bidentate ligands, cis-dichlorodiammine, diaminocyclohexane and ethylenediamine platinum(II), showed a distinct behavior, with a more important destabilization of the DNA structure in the nucleoprotein than the trans-bidentate ligand, trans-dichlorodiammine-Pt(II), and monodentate ligand, diethylenetriamine-Pt(II). The drastic decrease of the negative electric dichroism in the 260 nm absorption band of the bases, observed with the five ligands, indicates a profound alteration of the DNA arrangement in chromatin and nucleosomes, attributed to a condensation of its superhelical structure. Some differences with previous observations on DNA complexes with the same platinum compounds indicate the possible formation of protein-DNA crosslinks in chromatin and nucleosomes. These could have some importance for the biological effects.

Analysis of speckled fluorescent antinuclear antibody test antisera using electrofocused nuclear antigens

Antibodies to different components of the extractable nuclear antigen (ENA) have been thought to be serological markers for clinical subsets of rheumatic diseases. However, incomplete characterization and standardization of antigenic components such as ribonucleoprotein (RNP), Sm, and SS-B (Ha), and the multiplicity of autoantibodies produced by different patients have confounded correlations between autoantibody specificity and disease subsets. This study describes the preparative separation of the antigens Sm, RNP, and Ss-B (Ha) by electrofocusing and their use in a rocket electrophoretic assay that in one step identifies and quantifies the multiple reactivities of patient sera exhibiting the speckled FANA pattern. Preparative electrofocusing generates milligram quantities of these antigens with retention of their immunologic and biochemical characteristics, facilitating further study of their biological properties and relationships to disease subsets.

Heterogeneity of the spontaneously expanded and mitogen-induced generation of suppressor cell function of T cells on B cells in systemic lupus erythematosus

Eighty percent of 31 untreated patients with systemic lupus erythematosus (SLE) had abnormalities in their spontaneously expanded and/or Con-A-induced suppressor cell function, but the association of defects detected with both systems was only 68%. Loss of spontaneous suppression related positively to disease activity (r = 0.641) and the number of T gamma cells (r = 0.624) whereas Con-A-induced suppression correlated negatively with disease activity (r = -0.456) and the number of T gamma cells (r = 0.089). Incubation of mononuclear cells from SLE patients in antiribonucleoprotein IgG caused further loss of suppression in some, but not all, instances. The suppressor cell dysfunction found in SLE may result from diverse mechanisms, including a basic defect in the generation of suppressor cells and the abrogation of suppressor function by autoantibodies.

The extraction by micrococcal nuclease of glucocorticoid receptors and mouse mammary tumor virus DNA sequences is dissociated

Glucocorticoid receptors (RG) and mammary tumor virus (MM-TV) DNA sequences were extracted by micrococcal nuclease digestion from the nuclei of C3H mouse mammary tumor cells in order to specify their relative distribution in chromatin. RG was labelled and translocated into the nuclei by incubating cells with 3H Dexamethasone (3H Dex). The purified nuclei were then treated at 2 degrees C with micrococcal nuclease. Three chromatin fractions were successively obtained: an isotonic extract (ne3H1), ahypotonic extract (ne2) and the residual pellet (P). The Dex-RG complexes were measured by the hydroxyapatite technique. The MMTV DNA sequences were titrated by molecular hybridization with an excess of MMTV radioactive cDNA probe. Up to 75% of the nuclear 3H Dex and the MMTV radioactive cDNA probe. Up to 75% of the nuclear 3H Dex and MMTV DNA sequences were extracted in a concentration dependent manner while only 10-15% of nucleic acids became soluble in 10% perchloric acid. The extracted 3H Dex-RG complex was found to be partly bound to soluble chromatin and partly free. The free complex displayed similar sedimentation constants (4S, 7S) and DNA binding ability to the cytosol receptor. The 3H Dex-RG complexes were 2 to 8 fold more concentrated in ne1, which is known to be enriched in active chromatin, than in ne2. Conversely, the concentration of MMTV DNA sequences per microgram DNA was the same in the three nuclear fractions. These results suggest that the Dex-RG complexes are concentrated in an active fraction of chromatin. We propose that, among the 20-30 copies of MMTV genes per haploid genome, only a small proportion are transcribed or regulated.

Evidence for a subset of rheumatoid factors that cross-react with DNA-histone and have a distinct cross-idiotype

Cross-reactivity of a monoclonal rheumatoid factor with an antigen present on IgG and DNA-nucleoprotein was demonstrated, and evidence presented that the combining site of the antibody was involved in the reaction. The antigen on the DNA-nucleoprotein was shown to involve both DNA and histone fraction H2A + H2B and was trypsin sensitive. The relative binding affinity of the antibody appeared to be greater for IgG than the DNA-histone antigen. Similar polyclonal cross-reactive rheumatoid factors were found in a variety of diseases. A high incidence was found among patients with rheumatoid arthritis and mixed connective tissue disease. None were detected in patients with systemic lupus erythematosus and idiopathic cryoglobulinemia. Studies on one representative isolated polyclonal rheumatoid factor demonstrated the same reactivity with DNA-histone H2A + H2B as the monoclonal antibody. Cross-idiotype studies using antigen-binding inhibition methods demonstrated the same cross-idiotype on the polyclonal and the monoclonal rheumatoid factor which reacted with DNA-histone. This cross-idiotype was shown to be distinct from the cross-idiotypes previously demonstrated on monoclonal IgM proteins with anti-gamma-globulin activity.

Suppressor cell loss and dysfunction in mixed connective tissue disease

Of 11 patients with untreated mixed connective tissue disease (MCTD) who were studied, all had decreased circulating T gamma cells, and all but one had decreased suppressor cell function of T cells on B cells, determined by a reverse hemolytic plaque-cell assay. Results in 21 normal subjects were significantly, different. Incubation of mononuclear cells from MCTD patients in purified anti-ribonucleoprotein (anti-RNP) IgG resulted in further decrease in their suppressor function. Decrease of T gamma cells and their suppressor function may be due to in vivo penetration of anti-RNP antibody into T gamma cells, causing their deletion.

A method for high yield isolation and purification of anti-native DNA antibodies present in lupus sera

Antibodies to nucleic acids may serve as biochemical tools or as probes of cellular function. Particularly important, but also particularly difficult to obtain, is antibody which reacts exclusively with double stranded DNA. We describe here a method for the separation of antibodies to double stranded DNA from SLE serum, using hydroxyapatite to which DNA is adsorbed at a low molarity of phosphate buffer. Having applied the serum to the column we passed it through a continuous gradient of phosphate buffer ranging from 0.005 to 0.5 M. Deoxyribonuclease and magnesium ions were added when the gradient had reached the molarity at which single stranded DNA had already been desorbed and double stranded DNA began to be eluted. The antibody to native DNA that we obtained reacted in complement fixation, counterimmunoelectrophoresis and Farr's assay with native DNA and did not react with single stranded DNA, single and double stranded RNA or with a panel of 24 protein-coupled nucleosides, nucleotides and dinucleotides.

The role of enzymatic coupling of drugs to proteins in induction of drug specific antibodies

Isoniazid and hydralazine were covalently crosslinked by epidermal transglutaminase to serum and cell nuclear proteins. Albumin and nucleohistones were excellent acceptors of these drugs in serum and nuclear extracts, respectively. Drug-albumin and drug-histone conjugates were highly antigenic in rabbits within 4 weeks, eliciting drug-specific antibodies in all immunized animals. A radioimmunoassay for antibodies to isoniazid were developed, using a standard drug-albumin conjugate. The methods described here of enzymatic crosslinking of drugs to proteins facilitate studies of drug-induced hypersensitivity in animals and man.

Antibodies to histones in drug-induced and idiopathic lupus erythematosus

When tissue sections are extracted with 0.1 N HCl, cellular nuclear proteins, including histones, are removed but nuclear DNA is retained. Histones can be reconstituted back to nuclear DNA in acid-extracted tissue sections so that the resulting nuclear substrate is composed only of DNA and histones and does not contain acidic nuclear protein antigens. The resulting DNA-histone tissue substrate can be used in the immunofluorescent method for specific detention of antibodies to histones. Sera from 23 patients with drug-induced lupus erythematosus (procainamide 19, isoniazid 2, nitrofurantoin 2) and 20 patients with idiopathic (not drug-induced) systemic lupus erythematosus (SLE) were studied. All 23 patients with drug-induced lupus erythematosus (LE) lost nuclear staining on acid-extracted sections. In contrast, only 12 of 20 with idiopathic SLE lost nuclear staining on acid-extracted tissues, and in the remaining 8, there was no significant fall in titer. In the drug-induced LE group, loss of nuclear staining was due to the absence of histones on the substrate because with histone-reconstituted sections, 22 of 23 again became positive for nuclear staining at titers equal to or at one doubling dilution below titers on unextracted tissues. In contrast, of the 12 idiopathic SLE sera which lost nuclear staining, only 5 regained nuclear staining on histone-reconstituted tissue sections. In idiopathic SLE, antinuclear antibodies are heterogeneous in specificities and may consist of antibodies to native DNA, histones, or nonhistone proteins. In contrast, antinuclear antibodies in drug-induced LE are less heterogeneous and mainly consist of antibodies to histones.

Identification and characterization of two new soluble nuclear antigens reactive with sera of patients with connective tissue diseases

Two antigens, temporarily referred to as MU and TM antigens after the original serum, that are closely related to the nucleolus have been identified in the nuclear soluble extract. Both antigens reacted with the sera of a small number of patients with various connective tissue diseases, and both were different from antigens described previously in these disorders. MU antigen was sensitive to the digestion with RNase and trypsin, and was shown to be equivalent to the nuclear ribosomal components in the nuclear extract. TM antigen was resistant to the digestion with RNase and trypsin, and was localized in the nucleolus and extranucleolar portion of nuclei, but the precise nature of TM has not been established.

Nuclear translocation of the estradiol receptor: partial inhibition by ethidium bromide

Ethidium bromide (EB), an intercalating drug, has been shown to prevent the in vitro interaction of the estrogen receptor (R) with DNA (André et al., 1976). We have now studied the effect of this drug on the nuclear translocation of R in order to determine whether DNA integrity is needed for this translocation. In a cell-free reconstituted system made of purified nuclei and cytosol, the pretreatment of nuclei by EB prevented approximately half of the R nuclear translocation, but was unable to extract more than 17% of the E2-R previously translocated. A series of indirect evidences suggests that EB inhibits the nuclear translocation of R by interacting with nuclear DNA. The degree of the inhibition was related to the amount of drug bound to nuclei and was in agreement with the degree of ultrastructural modifications of chromatin. R was not irreversibly altered by the drug. The EB inhibition was only observed with DNA-containing particles and with estrogen receptor able to bind to DNA. In surviving uteri the drug also inhibited the R nuclear translocation. These resuts indicate two types of nuclear translocation of R, one sensitive and the other resistant to EB, and suggest that DNA is required for the EB-sensitive translocation.

Antinuclear antibodies (ANA): immunologic and clinical significance

The methods currently used for the detection of ANA have been analyzed, with emphasis on their practical application to the diagnosis of the CTD. The use of the indirect IF-ANA test was recommended as a screening procedure to detect ANA. The need to standardize the technique using a single substrate and fluorescent conjugates with uniform F/P ratios was stressed. Most importantly, the value of titrating ANA for the diagnosis of the CTD was discussed. ANA titers higher than 1/500 are usually very significant clinically, often found in spontaneous or drug-induced SLE and few other CTD. The immunologic aspects of ANA and their potential value as aids in the diagnosis and management of the CTD were discussed. Anti-nDNA antibodies have been found to have a high degree of specificity for SLE and high titers of these antibodies correlate well with low levels of serum complement and severity of kidney involvement. The spectrum of ANA in the sera from patients with SLE has been expanded with the finding of anti-Sm antibodies which, when detected by gel precipitation with prototype serum, have been found so far only in SLE. Some of these antibodies have been found to have prognostic significance. Patients with MCTD and a group of patients with SLE have high titers of serum ANA with specificity for an RNase-sensitive component of ENA. The group of SLE patients defined by the presence of these antibodies (anti-Mo) have a better prognosis and in general develop only mild nephritis or have no kidney involvement at all. High titers of pure antinucleolar antibodies probably are found almost exclusively in the sera of patients with scleroderma. Some ANA have organ specificity, and GS-ANA have been found in all patients with Felty's syndrome and in a large proportion of patients with RA. One of the great advances in the field has been the recognition that ANA can be induced in the human and in experimental animals by the use of a number of therapeutic agents. Some of these agents can also induce a clinical picture resembling spontaneous SLE, though kidney involvement does not occur or is extremely mild. It is interesting that the whole spectrum of ANA can be found in drug-induced LE except anti-nDNA antibodies which have been associated to the pathogenesis of immune complex nephritis in spontaneous SLE. There is no doubt that research on ANA has contributed a great deal to the understanding of the CTD and will continue to be a valuable tool for the clinician and the investigator.

Antibodies to histones and histone-histone complexes: immunochemical evidence for secondary structure in histone 1

Highly specific antibodies were raised to histone 1 (H 1) and the histone complexes H32-H42 AND H2A-H2B, isolated by salt extraction. Antibody to H1 could detect irreversible conformational changes in acid- or urea-treated H1. The antibodies showed different reactivities with chromosomes as compared to antibodies in acid-extracted histones and should be useful in studies of native chromatin and chromosome structure.

Percent satellite DNA as a function of tissue and age of mice

A selective loss of satellite DNA was found to occur to different extents as a function of tissue and age of mice using several common DNA extraction and purification procedures. This result emphasizes a serious problem that may be encountered in comparative studies of DNA structure and composition if selective loss of specific DNA sequences occurs. We have developed a DNA extraction and purification procedure that is simple and reliable and gives a high percent DNA yield, which substantially reduces the selective loss of heterochromatin DNA sequences. The method features a centrifugation step of a proteolytic digest of chromatin in 2.4 M CsCl. Percent DNA yield of 82-98% are routinely obtained with no apparent loss of satellite DNA sequences from different tissues or ages of mice. Utilizing this method, percent satellite DNA was found to remain essentially constant at 11 +/- 1% for spleen, kidney, and brain tissues obtained from mice of 10-780 days of age. However, for liver, percent satellite DNA remained at about 7-8% from 10 to 300 days of age and then increased to about 12-13% from 300 to 600 days of age. During this latter time interval (300-600 days), an increase of DNA per nucleus of about 3-fold occurred, due to the formation of tetra- and octaploid cell types. A steady loss in the total number of nuclei per gram of liver as a function of age was also found. These two opposing effects resulted in a nearly constant amount of DNA per gram and per organ for liver throughout the lifespan of the mouse.

Non-histone chromosomal proteins easily extractible from chick erythrocytes

Those non-histone chromosomal proteins which are easily extractible from chick erythrocytes differ substantially from proteins similarly extracted from other tissues of various species. Although a protein P1 was isolated along with histone H1 by extraction of calf thymus chromatin with HC1O4, the same procedure did not extract this protein from chick erythrocyte chromatin of either normal or regenerating blood. Likewise , non-histone proteins extracted with 0.35 M NaCl from calf thymus differed from those of normal chick erythrocytes, which were qualitatively identical but quantitatively inferior to those of regenerating blood. The major protein of about 25 000 molecular weight, totally extracted with 0.35 M NaCl from calf thymus, was not found in chick erythrocyte chromatin, but rather another major protein of about 35 000 molecular weight was partially extracted from erythrocytes.

Chromatin architecture: investigation of a subunit of chromatin by dark field electron microscopy

Dark field scanning electron microscopy of unstained, unfixed samples of chromatin, histone-1-depleted chromatin, and nucleohistone has been used to identify an apparent subunit of chromatin, namely a disk-shaped structure we term the unit particle, which is probably about 135 A wide and 50 A thick in the hydrated state. The unit particles are found at rather uniform intervals along thin DNA-like fibers. Histone 1 depletion leads to a bimodal distribution of these spacings. Our observations suggest that the unit particle consists of a loop of nucleoprotein, perhaps around a histone core.

Isolation of "speckled" nuclear antigen reactive with autoantibodies in patients with cancer and autoimmune diseases

An antigenic substance reactive with autoantibodies found in patients with cancer and autoimmune diseases was isolated from calf thymus. The purification procedure included extraction of the tissues with acetone powder, batch and column chromatography on DEAE-resins, ammonium sulfate precipitation, gel filtration on Sephadex G-200, and affinity chromatography on antibody-Sepharose 4B. Indirect immunofluorescence examination of cultured human embryo cells, using the serum of patients with nasopharyngeal cancer, showed a speckled nuclear pattern. The antigenic factor was a soluble acidic protein with a pI of 5.0 and a molecular weight of 250,000. The antigenic activities of this purified substance from calf thymus, and of the material on the cultured human embryo cells, were destroyed by proteases, ribonuclease, and alkaline phosphatase. The determinants were also sensitive to periodate oxidation. Thermal stability to 60 degree C and pH stability between 2.6 and 8.5 were demonstrated. Cross-reactivity of the antigenic substance with antibodies isolated from individuals with cancer and autoimmune diseases was shown by immunofluorescence, with appropriate blocking and absorption controls.

Generation of specific repeated fragments of eukaryote DNA

Calf-thymus DNA, hydrolyzed with a site-specific endonuclease from Haemophilus influenzae Rd, yields 12 discrete bands on polyacrylamide-agarose gels. These range in size from 7.5 x 10(4) to 2 x 10(6) daltons, and they represent about 5% of the total DNA with individual fragments comprising 0.1-1.5%. The various DNA segments are repeated between 1500 and 220,000 times per haploid genome. Whereas the wide range of reiteration frequencies suggests different origins for some of the fragments, the bias in fragment densities in CsCl and in Ag(+)-Cs(2)SO(4) toward those of known satellite DNAs suggests similar origins for some of them. Models for the possible origin of the DNA fragments can be grouped into three distinct, experimentally distinguishable, classes.

Spheroid chromatin units (v bodies)

Linear arrays of spherical chromatin particles (nu bodies) about 70 angstroms in diameter have been observed in preparations of isolated eukaryotic nuclei swollen in water, centrifuged onto carbon films, and positively or negatively stained. These bodies have been found in isolated rat thymus, rat liver, and chicken erythrocyte nuclei. Favorable views also reveal connecting strands about 15 angstroms wide between adjacent particles.