Targeted disruption of the genes, mlcR and ariB, which encode GAL4-type proteins in Penicillium citrinum

The role of two genes, mlcR and ariB, was investigated by gene disruption experiments. The mlcR gene in the ML-236B biosynthetic gene cluster of Penicillium citrinum encodes a putative 50.2-kDa protein with a Zn (II) 2Cys6 DNA-binding domain, and has similarity to most of the GAL4-type regulatory proteins. The mlcR disruptant did not produce ML-236B or its intermediates, suggesting that mlcR is involved in ML-236B biosynthesis. Transcriptional analysis of the mlcR disruptant by Northern hybridization and RT-PCR indicated that MlcR activates the transcription of mlcA, B, C,D, F, G and H in a pathway-specific manner. On the other hand, MlcR did not affect the transcription of mlcE and the genes outside the ML-236B cluster. The ariB gene, next to mlcR, encodes another GAL4-type protein. Transcriptional analysis of the ariB disruptant indicated that it is a transcriptional activator of the genes outside the ML-236B cluster, and is not related to ML-236B biosynthesis.