Zinc-dependent regulation of the Adh1 antisense transcript in fission yeast.

In yeast, Adh1 (alcohol dehydrogenase 1) is an abundant zinc-binding protein that is required for the conversion of acetaldehyde to ethanol. Through transcriptome profiling of the Schizosaccharomyces pombe genome, we identified a natural antisense transcript at the adh1 locus that is induced in response to zinc limitation. This antisense transcript (adh1AS) shows a reciprocal expression pattern to that of the adh1 mRNA partner. In this study, we show that increased expression of the adh1AS transcript in zinc-limited cells is necessary for the repression of adh1 gene expression and that the increased level of the adh1AS transcript in zinc-limited cells is a result of two mechanisms. At the transcriptional level, the adh1AS transcript is expressed at a high level in zinc-limited cells. In addition to this transcriptional control, adh1AS transcripts preferentially accumulate in zinc-limited cells when the adh1AS transcript is expressed from a constitutive promoter. This secondary mechanism requires the simultaneous expression of adh1. Our studies reveal how multiple mechanisms can synergistically control the ratio of sense to antisense transcripts and highlight a novel mechanism by which adh1 gene expression can be controlled by cellular zinc availability.