PubMed Health⌕ Search

Biomedical subjects

E Dickson

Publications and source records attributed to E Dickson.

At least 19 recordsLinked to original sources
PubMed1996

Formation of water-soluble porphyrins and protoporphyrin IX in 5-aminolevulinic-acid-incubated carcinoma cells.

The bioconversion of 5-aminolevulinic acid (ALA) into hydrophobic protoporphyrin IX and other water-soluble porphyrins was investigated in Ehrlich ascite carcinoma (EAC) cells and in a myeloma cell line. The effects of irradiation (514 nm), temperature, incubation time and added glucose on the relative porphyrin concentrations (protoporphyrin vs. water-soluble porphyrins) were examined. Variations in these parameters induced a change in the amount of water-soluble porphyrins relative to protoporphyrin IX. The main component of the hydrophilic porphyrins was found to be uroporphyrin (Up), with minor components of coproporphyrin (Cp) and other carboxyporphyrins. The enhanced production of water-soluble porphyrins appears to be associated with alterations in the activities of the various enzymes in the heme biosynthetic pathway, resulting, for example, in the reduction in the activity of mitochondrial enzymes.

Aminolevulinic Acid↗
PubMed1984

Structure and distribution of Alu family sequences or their analogs within heterogeneous nuclear RNA of HeLa, KB, and L cells.

We studied the distribution of repetitive sequence elements capable of forming double-stranded regions in nuclear RNA of HeLa, KB, and L cells. In human RNA populations, we called these regions duplex Alu family RNA (dAfRNA) because they represent transcripts of the highly reiterated family of DNA regions known as "Alu family DNA" (Rubin et al., Nature (London) 284:372-374, 1980). Although the dAfRNA populations of both human cell lines (HeLa and KB) have low sequence complexity, they represent 5% of the total heterogeneous nuclear RNA and have identical fingerprints; mouse L-cell dAf-like RNA (which has a similar complexity) represents only 2% of the total heterogeneous nuclear RNA and has an entirely different fingerprint. We utilized Escherichia coli RNase III as a highly specific reagent for the recognition of RNA:RNA duplex structure. This enzyme cleaves within the six characteristic RNase T1-resistant oligonucleotides of HeLa- and KB-cell dAfRNA (Robertson et al., J. Mol. Biol. 115:571-589, 1977). In addition, the size of heterogeneous nuclear RNA from all three cell types is reduced from greater than 32S to about 15S after RNase III treatment. We conclude that this size shift is a result of cleavage within dAfRNA regions and that such regions are present in most or all of the large RNA transcripts of these cells.

Animals↗
PubMed1980

Identification of the RNA region transferred from a representative primer, beta-globin mRNA, to influenza mRNA during in vitro transcription.

Capped eukaryotic mRNAs strongly stimulate influenza viral RNA transcription in vitro and donate their cap and also additional nucleotides to the viral transcripts (1). To identify which bases of a given primer mRNA are transferred, we synthesized influenza viral mRNA using a primer rabbit globin mRNA (enriched in beta-globin mRNA) which had been labeled in vitro to high specific activity with 125I. We show that during transcription the same 125I-labeled oligonucleotides were transferred to the 5' termini of each of the eight viral mRNA segments. The predominant sequence, representing 75 percent of the transferred oligonucleotides, was identical to the first 13 nucleotides at the 5' end of beta-globin mRNA (m7G5'ppp5'm6AmC(m)ACUUGCUUUUG). Because only the C-residues are labeled with 125I, these results indicate that either the first 12, 13 or 14 5' terminal bases of beta-globin mRNA were transferred to the viral mRNAs. 125I-labeled oligonucleotides recovered from the viral mRNA in minor yields indicated that shorter 5' terminal pieces of beta-globin mRNA were sometimes transferred and that G was probably the first base inserted by transcription.

Animals↗
PubMed1980

Specific RNA-cleaving activities from HeLa cells.

Subcellular fractionation of HeLa cells was carried out under gentle conditions to isolate enzymes that cleave RNA precursors in a specific manner. Four separate activities--cleavage of HeLa cell heterogeneous nuclear RNA, the HeLa cell 45S rRNA precursor, RNA . DNA hybrids (RNase H), and the Escherichia coli tRNATyr precursor (RNase P)--were revealed by these studies. The specificity and limited nature of these cleavages suggest that they are due to eukaryotic RNA-processing enzymes. The virtual absence of random nucleases from these enzymes was demonstrated by their inability to cleave the 8000-base early mRNA precursor of bacteriophage T7, E. coli 30S rRNA precursor, or HeLa cytoplasmic poly(A)-containing RNA.

Cell Nucleus↗
PubMed1979

Approaches to sequence analysis of 125I-labeled RNA.

A method is described for the initial steps of sequence analysis of RNase T1-and pancreatic RN-ase-resistant oligonucleotides of RNA containing cytidylate residues labeled in vitro with 125I. In many cases an oligonucleotide sequence can be deduced from a consideration of (i) its relative position in the two-dimensional fingerprint (with DEAE thin layer homochromatographic second dimension), (ii) its electrophoretic mobility on DEAE paper at pH 1.9, and (iii) identification of its products of further enzymatic digestion by comparison with a set of marker oligonucleotides. Additional methods including analysis of oligonucleotides following chemical blocking of uridylate residues with CMCT and analysis of products of incomplete enzymatic digestion are also discussed.

Base Sequence↗
PubMed1977

A nucleotide sequence from a ribonuclease III processing site in bacteriophage T7 RNA.

Transcription of that portion of the bacteriophage T7 genome encoding early functions yields RNA molecules about 7500 nucleotides long representing this entire early region. These long transcripts can be cleaved in vitro by highly purified Escherichia coli ribonuclease III (endoribonuclease III; EC 3.1.4.24), yielding five messenger RNAs identical to those produced in vivo. During this reaction, a small RNA fragment called F5 RNA is released, which is specified by the region of the T7 genome between genes 1.1 and 1.3. The following sequence of 32P-labeled F5 RNA has been determined using standard RNA sequencing techniques: pU-A-A-G-G-U-C-G-C-U-C-U-C-U-A-G-G-A-G-U-G-G-C-C-U-U-A-G-Uoh. The relative contributions of sequence and structure to ribonuclease III processing signals are considered in light of these findings.

Base Sequence↗
PubMed1976

Potential regulatory roles for RNA in cellular development.

In addition to its widely accepted messenger and structural roles, RNA has been implicated in several other biological events: transfer of specificity of the immune response, interferon induction, and infection of plants by viroids. In none of these cases is the mechanism of RNA action understood. As a result of recent advances in the understanding of RNA metabolism in eukaryotic nuclei and potential specificity of nucleases that cleave such RNA, we have suggested specific ways in which "extra" RNA could be involved in regulation of the development of cells. A survey of literature concerning mammalian cell differentiation both in embryos and in the immune system leads to the observation that there appears to be a line of communication between macromolecules on cell surfaces and the genome. Making the conservative assumption that the DNA retains its integrity throughout development, it seems likely that highly specific signals are sometimes required to transfer information from outside the cell to the DNA,resulting in a change in state of differentiation. We propose a way in which RNA could be utilized in this process.

Animals↗
PubMed1973

Application of fingerprinting techniques to iodinated nucleic acids.

Several techniques of RNA and DNA finger-printing and determination of sequence have been applied to nucleic acids labeled with (125)I. Fingerprints of human 5S RNA and bacteriophage f2 RNA resemble those of their noniodinated counterparts both in complexity and in specific pattern. Iodination as used here is thus a general labeling procedure, and appears principally to label cytidine residues. This iodination method shows little sensitivity to potential structure in single-stranded RNA molecules, yields stable oligonucleotide products in a reproducible manner, and does not change the specificity of several ribonucleases and deoxyribonucleases.

Animals↗