Identification of the specific sequence recognized by Penicillium citrinum MlcR, a GAL4-type transcriptional activator of ML-236B (compactin) biosynthetic genes

MlcR is a pathway-specific transcriptional activator of the ML-236B biosynthetic genes in Penicillium citrinum. The MlcR-binding sequences were identified by an in vitro gel-shift assay and an in vivo reporter assay for the region between mlcA and mlcC as a model. The gel-shift assay showed that recombinant MlcR bound to the DNA sequence 5′-ACGGCGTTATTCGG-3′ and most of the bases in this motif were required for the interaction between MlcR and DNA. In the reporter assay using β-glucuronidase (GUS), substitution of the bases in this binding sequence resulted in the drastic reduction of GUS activities. These data clearly indicate that this MlcR-binding sequence is essential for the transcriptional activation of mlcA and mlcC in P. citrinum. Similar motifs were found in other loci of the ML-236B biosynthetic gene cluster and the consensus-binding motif for MlcR was predicted to be a direct repeat, 5′-WCGG-N6-TCGG-3′.