The response time of transcription and translation of the leu-2 gene of Neurospora to its inducer, alpha-isopropylmalate, approaches the permissible minimum.

The rate of transcription and translation of the leu-2 gene of Neurospora crassa was measured after induction by alpha-isopropylmalate. Little message of enzyme was found before inducer addition but transcription in the lower eukaryote was found well underway within five minutes after inducer addition, followed in a minute or two by the appearance of functional enzyme. The timing was close to the limit set by RNA synthesis and ribosome procession. As a consequence, it seems unlikely that traversal of the cell and/or nuclear membranes by the inducer and message involves intermediate synthetic reactions and that the leu-3 positive regulatory element is fully available for participation in the induction process before the inducer is added. A significant overshoot in message synthesis was found early in the induction process. This is discussed with respect to previously observed effects of the inducer on general RNA synthesis.