Regulation of the maximal rate of RNA synthesis in the fission yeast Schizosaccharomyces pombe.

Of interest to many biologists is how growth, e.g., RNA synthesis, and cell division are mutually controlled. One method of establishing the nature of the control is to determine what "factors" are limiting when cells synthesize RNA at a maximal rate. The transcription maximum (maximum rate of RNA synthesis) has been determined in cell division mutants that continue to grow but fail to divide to determine if there is a cell cycle control over RNA synthesis. There is no correlation between transcription maximum and DNA synthesis or septation which suggests that these events do not exert a direct cell cycle control over RNA synthesis in exponentially growing cells. In addition, the lack of strong correlation between the transcription maximum and cell size or gene dosage indicates that the rate of RNA synthesis is not directly regulated by either of these parameters. The possibility that the maximum rate is determined by a concentration effect of an end product which acts in the nucleus, such as a specific RNA or protein, could not be ruled out and evidence is presented in support of such a model.