Phorbol ester facilitates apoptosis in murine fibroblasts pretreated by mild ultraviolet radiation.

Although phorbol 12-myristate 13-acetate (PMA) inhibits apoptosis and promotes the growth of some types of cells, it induces apoptosis in other cells. We evaluated the apoptotic effects of PMA on murine fibroblasts (L-929) that had been exposed to ultraviolet-B (UV-B) radiation at 312 nm, which promotes tumor cell growth. Exposure to PMA alone did not induce Fas, Fas-L, or apoptosis. Cells exposed to mild UV-B irradiation (80 J/m(2)) alone exhibited a slight expression of Fas and Fas-L 36 to 48 h after the exposure, and exhibited apoptosis as evidenced by DNA fragmentation 72 h after exposure. The addition of PMA (0.8 x 10(-5) to 3.2 x 10(-5) M) to the medium 24 h after the UV-B exposure markedly and dose-dependently enhanced these cell responses. Confluent untreated cells, cells cocultured with PMA, and cells cocultured with PMA for 24 h after the UV-B exposure consistently expressed mRNAs for wild-type p53, bcl-2, and ICE. Expression of c-myc mRNA was initially observed, but became undetectable in the cells cocultured for 24 h with a high concentration of PMA (3.2 x 10(-5) M) following UV-B exposure. Such cells subsequently exhibited the maximal apoptotic response. We conclude that mild exposure to UV-B altered murine fibroblast cells in such a way as to facilitate their death by apoptosis upon addition of PMA.     

Protein polymorphism in a feral population of the pigeon Columba livia domestica

Sixteen enzymatic and non-enzymatic proteins of the pigeon Columba livia domestica were examined electrophoretically. These proteins were presumed to be under control by 22 loci. Of the 22 loci, 6 were defined as polymorphic and 15 as monomorphic. Another locus was variable, but the variation was not genetically interpretable. Average heterozygosity calculated over 21 loci was 0.075.     

Cleavage of double helical DNA by Cu2+ ion in the presence of bisintercalator containing penta(ethylene glycol) connector chain

In designing new DNA recognizing and cleaving reagents, we introduce herein a bisacridine derivative (referred to as bisacridine) in which two acridine heterocycles are connected by a penta(ethylene glycol) bridging chain. This compound offers two possible functions: 1, stabilization of DNA bisacridine intercalator complex by metal ion. The penta(ethylene glycol) chain stabilizes metal ions binding to the phosphate site of DNA, where the penta(ethylene glycol) chain constitutes a part of a pseudomacrocyclic ligand for metal binding; and 2, enhancement of metal-assisted hydrolytic cleavage of DNA by means of a metal concentration effect by the pseudomacrocyclic ethereal chain. The binding isotherms of bisacridine with DNA in the presence of metal ions showed that the binding was mainly governed by the cation exchange reaction on the anionic DNA polymer chain, i.e., the exchange between metal ions and the cationic bisacridine. The bisacridine showed an increase DNA binding ability compared to quinacrine, the monoacridine counterpart, and caused an enhancement of DNA cleavage in the presence of Cu2+ ions. Additional experiments which included DNase 1 footprinting in the presence of bisacridine and the DNA cleavage by Cu2+/bisacridine using a 32P end-labelled DNA fragment, suggested that the Cu2(+)-assisted DNA cleavage sites in the presence of bisacridine were in reasonable overlap with the DNA binding sites of bisacridine.     

Genetic analysis of a mutation affecting ribosomal protein S1 in Escherichia coli

Molecular Genetics and Genomics - Ribosomal protein S1 from a newly isolated Escherichia coli mutant has a molecular weight of about 54,000 which is smaller than the wild type S1 (M.W. 65,000). The...     

Cell-specific properties of red cell and liver ferritin from bullfrog tadpoles probed by phosphorylation in vitro

Cell-specific differences occur in the primary structure of ferritin. For example, red cell and liver ferritin from bullfrog tadpoles differ by 1.5 times in serine content. To determine if cell-specific differences in ferritin primary structure are expressed in the tetraeicosomer, which thus might distinguish the proteins in a functional state, phosphorylation in vitro was employed as a probe using [gamma-32P]ATP and the catalytic subunit from the cAMP-dependent protein kinase of bovine skeletal muscle. Subunits of both proteins in the tetraeicosomers were phosphorylated. Based on tryptic peptide maps, five regions common to both red cell and liver apoferritin were phosphorylated, as confirmed for two peptides by amino acid analyses. [32P]Apoferritin from red cells yielded an additional four 32P-fragments by mapping, at least three of which were unique by amino acid analysis and, in one case, might represent a 32P-Fe complex bound by a fragment of the iron-binding site. One peptide appeared to be unique to liver apoferritin. High concentrations of ATP yielded one additional peptide common to liver and red cell and one red cell-specific peptide in the tryptic peptide maps. The maximum moles of 32P/molecule were 13 +/- 4 and 6 +/- 2, respectively, for red cell and liver apoferritin, which corresponded within experimental error to the number of 32P-tryptic peptides. The level of phosphorylation was, on the average, not more than one site/subunit. Furthermore, above certain levels of phosphorylation, some subunits in the assemblage of 24 appeared to be unavailable as substrates, possibly because of charge repulsion or conformational changes. The possibility that post-translational modifications of ferritin which amplify cell-specific structural features occur in vivo with cytoplasmic components, e.g. protein kinases, is considered in terms of the physiological availability of iron from different iron storage cells and developmental changes in iron storage.