RESUMO
A molecular clone containing the complete sequence of a mitochondrial circular plasmid-like DNA (the R plasmid) isolated from the date-palm variety V3DP was used as a probe in Southern analyses of mitochondrial DNA prepared from other varieties. Another circular structure (the S plasmid) was detected in some of these varieties, and sequenced from variety V2DP. It appears that the R plasmid could have arisen from the S plasmid by an intermolecular recombination event at a set of 26-bp imperfect short direct repeats.
Assuntos
DNA Mitocondrial/genética , DNA de Plantas/genética , Plantas/genética , Recombinação Genética , Sequência de Bases , DNA Circular/genética , Dados de Sequência Molecular , Plasmídeos/genética , Sequências Repetitivas de Ácido Nucleico , Homologia de Sequência do Ácido NucleicoRESUMO
The relative amounts of iso-tRNAsGly and iso-tRNAsPro existing in chick embryo tendon are indicative of a specialization of the tRNA population for collagen synthesis. These amounts are not modified (i) in primary avian tendon (PAT) cells in culture for which the procollagen production varies from about 10% of total protein synthesis to 60% and (ii) in tendons from immature chicks, which show a 3-fold decrease of procollagen production with increasing age. The characteristic tRNA pattern was not maintained in cells which had lost the ability to make high levels of collagen as observed in the cases of: (i) PAT cells reaching confluency; (ii) virus-transformed PAT cells and (iii) tendon from adult chick. Our data are consistent with the idea that tendon tRNA specialization for collagen synthesis is a differentiation feature independent of the expression level of the collagenic function but related to its maintenance.
Assuntos
Pró-Colágeno/biossíntese , RNA de Transferência Aminoácido-Específico/genética , RNA de Transferência de Prolina/genética , Tendões/metabolismo , Envelhecimento , Animais , Ácido Ascórbico/farmacologia , Vírus do Sarcoma Aviário/genética , Divisão Celular , Transformação Celular Neoplásica , Células Cultivadas , Embrião de Galinha , Galinhas , Cinética , Pró-Colágeno/genética , RNA de Transferência de Prolina/efeitos dos fármacos , RNA de Transferência de Prolina/isolamento & purificação , Tendões/citologia , Tendões/crescimento & desenvolvimentoRESUMO
The relation between codon usage and tRNA content for proline and glycine, the major constituents of collagen, was studied in two tissues: the magnum of laying hen oviduct and the leg tendons of chick embryo where collagen is produced. Although the relative contents of tRNA(GCCGly) and tRNA(IGGPro) in tendons, as compared to magnum indicate a specialization of the tRNA population for collagen synthesis, the distribution of the preponderant codons in collagen mRNA is correlated but at a lesser extent to that of their cognate tRNAs.
