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R E Gross

Publications and source records attributed to R E Gross.

At least 19 recordsLinked to original sources
PubMed1990

Regulation of the expression of the regulatory subunit of cAMP-dependent protein kinase II beta in Friend erythroleukemic cells. Evidence for posttranscriptional control and a central role for the C subunit.

Friend erythroleukemic cells provide a system for studying the regulation of the expression of regulatory (R) and catalytic (C) subunit isoforms of cAMP-dependent protein kinases. Friend cells contain RI alpha, two RII subunits previously designated RII-52 and RII-54, and C alpha. When the cells are treated with 0.2 mM methylisobutylxanthine (MIX) and either 20 microM forskolin or 0.5 mM 8-Br-cAMP, RI alpha content declines 50-75% because of a large decrease in the t1/2 value for the dissociated RI alpha subunit; RII-54 expression is invariant, but the amount and rate of synthesis of RII-52 increases 10-15-fold (Schwartz, D. A., and Rubin, C. S. (1985) J. Biol. Chem. 260, 6296-6303). We now demonstrate that RII-52 and RII-54 correspond to RII beta and RII alpha, respectively. When cAMP levels are elevated in Friend cells the abundance of the 3.3-kilobase RII beta mRNA increases 25-30-fold in parallel with the rate of RII beta subunit synthesis indicating that pretranslational control is operative. Other R and C mRNAs are not markedly induced. Surprisingly, the rate of transcriptional initiation of the RII beta gene and the stability of RII beta mRNA are not altered during RII beta induction. Rather, the induction of RII beta mRNA is associated with the accumulation of major (3.4 kilobases) and minor (4 kilobases) RII beta pre-mRNAs in the nucleus. It appears that the cAMP signal-transduction system alters a nuclear protein(s) such that either the proportion of RII beta pre-mRNAs that are processed to mature mRNAs and are exported to the cytoplasm is greatly increased or the nuclear precursors are stabilized. Thus, regulation is exerted at a posttranscriptional level. In order to establish directly a causal role for C in RII beta induction and to rule out artifacts introduced by the use of drugs such as forskolin, MIX, and cAMP analogs we stably transfected Friend cells with a vector containing C alpha cDNA under the regulation of the zinc-activated metallothionein I promoter. The addition of 0.15 mM ZnSO4 caused the accumulation of dissociated C subunits and the selective induction of RII beta.

1-Methyl-3-isobutylxanthine↗
PubMed1990

Cloning, characterization, and expression of the gene for the catalytic subunit of cAMP-dependent protein kinase in Caenorhabditis elegans. Identification of highly conserved and unique isoforms generated by alternative splicing.

The nematode Caenorhabditis elegans expresses substantial amounts of several forms (Mr values = 39,000-41,000) of the catalytic subunit (C) of cAMP-dependent protein kinase. Approximately 65% of the total cAMP-dependent phosphotransferase activity is recovered in particulate fractions of homogenates prepared from asynchronous populations of C. elegans. The C subunit is expressed at a low level in cytosolic and particulate compartments during embryogenesis. As the nematodes progress from late embryonic stages to the newly hatched, first larval (L1) stage, C subunit content increases 15-fold. High levels of C subunits are observed in several subsequent larval and adult stages of development. Since the relative abundance of C subunit mRNA changes little with development, it appears that control of C expression is exerted the translational and/or post-translational levels. cDNAs for two types of C have been cloned and sequenced. The derived amino acid sequence of a major isoform (CeCAT alpha, 358 residues) is highly homologous (82% identical) with the murine C alpha subunit. A second, novel C subunit (CeCAT alpha', 374 residues) has a unique 56-residue carboxyl-terminal region that is generated by the alternative splicing of the C pre-mRNA. The splicing process that yields CeCAT alpha' is unusual because it converts the central portion of an apparent 1-kilobase (kb) intron to an exon. The alternative exon introduces the novel carboxyl terminus and a new translation stop signal, while simultaneously converting the coding sequence for 40 carboxyl-terminal residues in CeCAT alpha into 3'-untranslated nucleotides. The 5' end of the C. elegans C subunit mRNA is produced by the trans-splicing of the C gene transcript to a 22-base pair C. elegans leader sequence originally described by Krause, M., and Hirsh, D. [1987) Cell 49, 753-761). The 20-kb C. elegans C gene is divided into seven exons by introns ranging in size from 54 to 8000 bp. The sizes of the C. elegans C subunit gene, cytoplasmic mRNA (2.5 kb), and subunit protein are similar to the sizes of the murine C alpha gene, mRNA, and polypeptide. However, the nematode and murine C genes differ significantly in the organization of their introns and exons.

Amino Acid Sequence↗
PubMed1990

Cloning, structure, and expression of the gene for a novel regulatory subunit of cAMP-dependent protein kinase in Caenorhabditis elegans.

The nematode Caenorhabditis elegans (C. elegans) expresses the regulatory subunit (R) of cAMP-dependent protein kinase at a level similar to the levels determined for R subunits in mammalian tissues. Approximately 60% of the C. elegans cAMP-binding protein is tightly associated with particulate structures by noncovalent interactions. Ionic detergents or 7 M urea solubilize particulate R. Solubilized and cytosolic R subunits have apparent Mr values of 52,000 and pI values of 5.5. cDNA and genomic DNA encoding a unique C. elegans R subunit were cloned and sequenced. The derived amino acid sequence contains 375 residues; carboxyl-terminal residues 145-375 are 69% identical with mammalian RI. However, residues 44-145 are markedly divergent from the corresponding regions of all other R sequences. This region might provide sufficient structural diversity to adapt a single R subunit for multiple functional roles in C. elegans. Antibodies directed against two epitopes in the deduced amino acid sequence of C. elegans R avidly bound nematode cytosolic and particulate R subunits on Western blots and precipitated dissociated R subunits and R2C2 complexes from solution. Immunofluorescence analysis revealed that the tip of the head, which contains chemosensory and mechanosensory neurons, and the pharyngeal nerve ring were enriched in R. The R subunit concentration is low during early embryogenesis in C. elegans. A sharp increase (approximately 6-fold) in R content begins several hours before the nematodes hatch and peaks during the first larval stage. Developmental regulation of R expression occurs at translational and/or post-translational levels. The 8-kilobase pair C. elegans R gene is divided into 8 exons by introns ranging from 46 to 4300 base pairs. The 5'-flanking region has no TATA box and contains preferred and minor transcription start sites.

Amino Acid Sequence↗
PubMed1984

Radiographic film fog in the darkroom.

One of the most common and yet also most preventable problems in the radiology department is unnecessary darkroom fogging of x-ray film, which can degrade image quality to the extent that the procedure must be repeated. Such problems can be overcome by identifying and eliminating sources of fog, such as incorrect safelight filters, excessive safelight wattage, using too many safelights or placing them too close to the work area, light leaks, and indicator lights on telephones, silver recovery units, timers, or other electrical devices.

Technology, Radiologic↗