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D E Comings

Publications and source records attributed to D E Comings.

At least 145 records · Page 8Linked to original sources
PubMed1980

Arrangement of chromatin in the nucleus.

The factors responsible for producing some degree of order to the arrangement of chromatin in the nucleus are reviewed. They are following: 1. Chromosomes are attached to the nuclear membrane, nucleolus and intranuclear matrix. As a result they have a relatively fixed position in the nucleus. 2. In some species somatic pairing results in alignment of homologs. This is rare in mammals. 3. The association of ribosomal DNA and 5S DNA with the nucleolous results in the close approximation of the chromosomes carrying these DNA sequences. In man and other animals the most obvious consequence is satellite association. 4. Heterochromatin is condensed onto the inner nuclear membrane and periphery of the nucleolous while genetically active chromatin occupies the more central portion of the nucleus. The results is a peripheral location of late replicating DNA and a central location of early relicating DNA. 5. The DNA replication points tend to be associated with the nuclear matrix. Autoradiography of briefly labelled cells shows a high frequency of grains associated with nuclear matrix material. 6. Heterochromatin association results in chromocenters and ectopic pairing. 7. In addition to all these is the Rabl orientation or alignment of centromeres with centromeres and telomeres with telomeres. This polarization of the chromosomes results from the traction on the centromeres by the spindle fibers. There is no firm evidence for any higher degrees of order that might bring specific functioning genes into close proximity.

Animals↗
PubMed1980

Normal two-dimensional gel electrophoresis of alpha-2-macroglobulin in cystic fibrosis.

Some studies have suggested that a mutant form of alpha-2-macroglobulin (alpha-2-M) could be the primary defect in cystic fibrosis (CF). To test for the presence of charge change amino acid substitutions, alpha-2-M was examined by two-dimensional gel electrophoresis following complete denaturation of the proteins. The pattern of nine charge isomers observed was the same in homozygous, heterozygous, and normal individuals.

Blood Protein Electrophoresis↗
PubMed1980

A search for protein cores in chromosomes: is the scaffold an artifact?

A protein chromosome scaffold structure has been proposed that acts as a structural framework for attachment of chromosomal DNA. There are several troubling aspects of this concept: (1) such structures have not been seen in many previous thin-section and whole-mount electron microscopy studies of metaphase chromosomes, while they are readily seen in leptotene and zygotene chromosomes; (2) such a structure poses problems for sister chromatid exchanges; and (3) the published photographs show a marked variation in the amount of scaffold in different whole-mount preparations. An alternative explanation is that the scaffold in whole-mount preparations represents incomplete dispersion of the high concentration of chromatin in the center of chromosomes, and when the histones are removed and the DNA dispersed, the remaining nonhistone proteins (NHPs) aggregate to form a chromosome-shaped structure. Two studies were done to determine if the scaffold is real or an artifact: (1) Chinese hamster mitotic cells and isolated chromosomes were examined using two protein stains -EDTA-regressive staining and phosphotungstic acid (PTA) stain. The EDTA-regressive stain showed ribonucleoprotein particles at the periphery of the chromosomes but nothing at the center of the chromosomes. The PTA stain showed the kinetochore plates but no central structures; and (2) isolated chromosomes were partially dispersed to decrease the high concentration of chromatin in the center of the chromosome, then treated with 4 M ammonium acetate or 2 M NaCl to dehistonize them and disperse the DNA. Under these circumstances, no chromosome scaffold was seen. We conclude that the scaffold structure is an artifact resulting from incomplete dispersion of central chromatin and aggregation of NHPs in dehistonized chromosomes.

Animals↗
PubMed1979

Nuclear proteins. VI. Fractionation of chromosomal non-histone proteins using hydrophobic chromatography.

Mouse liver non-histone proteins, isolated by hydroxyapatite chromatography, were fractionated by hydrophobic chromatography using omega-amino-decyl-agarose omega-amino butyl-agarose, decyl-agarose, butyl-agarose, phenyl-Sepharose, and CPAD-Sepharose. Two column loading techniques were used. In the 0.35 M NaCl technique, the proteins were dialized into 0.35 M NaCl, applied to the column and initially eluted with 0.35 M NaCl. In the 40% (NH4)2SO4 technique, the non-histone proteins were mixed with the hydrophobic agarose, dialized against 40% (NH4)2SO4, and initially eluted with 40% (NH4)2SO4. In both cases the columns were subsequently eluted with 10 mM Tris-HCl, pH 7.5, 0.35, 1.0 and 5.0 M LiBr, and finally with 1% sodium dodecyl sulfate. The 0.35 M NaCl technique, using decyl-agarose and phenyl-Sepharose, resulted in a single step marked enrichment of the major hnRNA proteins (1 M LiBr fraction). The 40% (NH4)2SO4 technique resulted in a single step isolation of a pair of 15-20 000 dalton polypeptides.

Animals↗
PubMed1979

Two-dimensional gel electrophoresis of 125I-labeled surface proteins of human fibroblasts.

Human fibroblasts were labeled by the 125I-lactoperoxidase technique and the sodium dodecyl sulfate soluble proteins examined by two-dimensional gel electrophoresis to determine the charge heterogeneity of the surface proteins and test for differences in surface proteins in several hereditary disorders. Approximately 80 polypeptides were observed. Those below 65 000 daltons tended to occur as single spots, while those of higher molecular weight were often present as a series of polypeptides of similar molecular weight (charge isomers). The possible role of these proteins in cell-cell recognition is discussed.

Cell Line↗
PubMed1979

Higher order structure of chromosomes.

Isolated Chinese hamster metaphase chromosomes were resuspended in 4 M ammonium acetate and spread on a surface of distilled water or 0.15 to 0.5 M ammonium acetate. The DNA was released in the form of a regular series of rosettes connected by interrossette DNA. The mean length of the rosette DNA was 14 micron, similar to the mean length of 10 micron for chromomere DNA of Drosophila polytene chromosomes. The mean interrosette DNA was 4.2 micron. SDS gel electrophoresis of the chromosomal nonhistone proteins showed them to be very similar to nuclear nonhistone proteins except for the presence of more actin and tubulin. Nuclear matrix proteins were present in the chromosomes and may play a role in forming the rosettes. Evidence that the rosette pattern is artifactual versus the possibility that it represents a real organizational substructure of the chromosomes is reviewed.

Actins↗
PubMed1979

Pc 1 Duarte, a common polymorphism of a human brain protein, and its relationship to depressive disease and multiple sclerosis.

Pc 1 Duarte, a common variant of a human brain-specific protein, is present in one-third of the control population and has a gene frequency of 0.17. There was a significantly increased frequency of mutant heterozygotes and homozygotes among individuals with depressive disease. This is consistent with a model in which Pc 1 Duarte is the major gene in depressive disease, acting in conjunction with an environmental threshold effect.

Black People↗
PubMed1979

Triple-spot proteins in two-dimensional gel electrophoresis.

A triple-spot pattern of polypeptides occurring in two-dimensional gel electrophoresis of proteins is described. The presence of a mutant protein, Pc 1 Duarte, which results in a splitting of all three polypeptides, is evidence that they are produced by the same gene. This pattern is seen in about 1% of the proteins from a variety of sources. Typically, about 50% of the protein occurs as a single major spot, the remainder occurring as two polypeptides with an additional negative charge and slightly different molecular weight. The reproducibility of this pattern implies a functional significance which is presently unknown. The implication of this configuration for patterns seen by one-dimensional gel electrophoresis is discussed.

Animals↗
PubMed1978

Specific interaction between mouse liver non-histone chromosomal proteins and mouse DNA demonstrated by a sequential DNA-protein binding procedure.

The binding of mouse liver chromosomal proteins to DNA has been investigated using the nitrocellulose filter binding technique. Careful purification of the DNA involving nuclease S1 digestion and prefiltration through a nitrocellulose filter is used to reduce background binding in the absence of protein to less than 1%. Procedures involving direct binding of protein to labeled DNA, competition of binding of labeled DNA by unlabeled DNA, and dissociation of DNA . protein complexes with time do not indicate significant preference for binding to mouse DNA relative to Escherichia coli DNA. This specificity is demonstrated much more clearly by a novel type of procedure, which we call a sequential binding procedure. In this procedure non-specific binding proteins are sequestered by incubation with an excess of unlabeled E. coli DNA prior to addition of labeled DNA. Under these conditions, labeled mouse DNA is bound to filters to a 3- to 4-fold greater extent than labeled E. coli DNA.

Animals↗
PubMed1978

Nuclear proteins. V. Studies of histone-binding proteins from mouse liver by affinity chromatography.

We examined four extracts of mouse liver for histone-binding proteins using histone affinity chromatography and positively charged resins. The extracts used were cytoplasm and washes from isolated nuclei with buffers containing 0.05 M Tris, 0.15 M NaCl or 0.35 M NaCl. Proteins from the nuclear washes showed greater binding to the columns than proteins from the cytoplasm. The binding fractions were heterogeneous in gel electrophoresis systems. Proteins bound to affinity columns of individual histones were similar to those bound to columns of whole histone, polylysine and DEAE. A 25,000 dalton polypeptide (J2), found only in nuclear washes was a prominent histone-binding protein. It could be competitively eluted from DEAE with histones, suggesting polypeptide J2 may show a specific affinity for histones. Polypeptide J2 has an acidic to basic amino acid ratio of 1.58, and its amino acid composition is not similar to that of the high mobility group 1 protein. Polypeptide J2 binds to hydrophobic columns and may play a role in modifying histone-histone and histone-DNA interactions.

Amino Acids↗
PubMed1978

DNA-binding properties of nuclear matrix proteins.

Mouse nuclear matrix proteins, examined by a filter assay, were found to bind to DNA. There was no preference for homologous mouse compared to heterologous E. coli DNA. Competition assays showed a preference for AT-rich DNA and of the 4 single-stranded homopolymers there was a preference for poly(dT). These observations are consistent with the possibility that the matrix may play a role in the formation of AT-rich chromomeres (G-bands).

Animals↗