Polyribosomes and unstable messenger RNA. III. Temporal relationship between the syntheses of mRNA and inducible enzymet

Abstract

Kinetic aspects of the synthesis of induced enzyme and its labile mRNA under a variety of experimental conditions have been analysed on the basis of a model of protein synthesis reported in earlier papers. Temporal relationship between the syntheses of mRNA, defined as the total amount of RNA in a cell hydridizible to homologous DNA and inducible enzyme predicted by these analyses is found to be compatible with experimentally observed behaviour. The rate of enzyme synthesis is shown to vary non-linearly with the amount of mRNA as estimated from DNA-RNA hybridization or from enzyme-forming capacity. The analyses provide a useful guide-line for an evaluation of the coupling between transcription, translation and degradation of mRNA in an in vivo system. The nature of discontinuities in the kinetic curves for induced enzyme synthesis, arising from a periodic and synchronous transcription of mRNA, is also discussed. The analysis is supplemented by experimental observations on the synthesis of β-galactosidase under conditions of synchronous transcription of mRNA.