Transcriptional interference in the methylotrophic yeast, Pichia pastoris

Transcription is regulated by the antagonistic activities of activator and repressor proteins binding to distinct promoter sequences. When an activator and repressor exhibit the same DNA binding specificity, competition for binding to the same promoter binding site may lead to transcriptional interference. We have identified one such competing module in Pichia pastoris, a methylotrophic yeast, widely used for commercial production of recombinant proteins. The activator-repressor combo comprises of two zinc finger transcription factors known as Mxr1p and ROP which bind to DNA sequences containing 5’ CYCCNY 3’ motif present in the promoters of genes encoding enzymes required for the metabolism of methanol such as the alcohol oxidase I (AOXI). While binding of Mxr1p results in transcriptional activation, ROP binding results in repression. The lecture will focus on the experimental approach used in these studies, key results and conclusions as well as the importance of understanding regulation of methanol metabolism in P. pastoris.