Dependent on phosphate availability the yeast Saccharomyces cerevisiae expresses either low or high affinity phosphate transporters. In the presence of phosphate yeast cells still express low levels of the high affinity phosphate transporter Pho84. The regulator Spl2 is expressed in approximately 90% of the cells, and is not expressed in the remaining cells. Here we report that deletion of RRP6, encoding an exonuclease degrading non-coding RNA, or BMH1, encoding the major 14-3-3 isoform, resulted in less cells expressing SPL2 and in increased levels of RNA transcribed from sequences upstream of the SPL2 coding region. SPL2 stimulates its own expression and that of PHO84 ensuing a positive feedback. Upon deletion of the region responsible for upstream SPL2 transcription almost all cells express SPL2. These results indicate that the cell-to-cell variation in PHO84 and SPL2 expression is dependent on a specific part of the SPL2 promoter and is controlled by Bmh1 and Spl2.

根据磷酸盐的可用性，啤酒酵母表达低亲和力或高亲和力的磷酸盐转运蛋白。在存在磷酸盐的情况下，酵母细胞仍然表达低水平的高亲和力磷酸盐转运蛋白Pho84。调节子Spl2在大约90％的细胞中表达，而在其余细胞中不表达。这里我们报道缺失RRP6，编码外切核酸酶降解的非编码RNA，或BMH1，编码主要同种型14-3-3，导致表达更少的细胞SPL2从序列和在增加的RNA水平转录的上游SPL2编码地区。SPL2刺激其自身表达以及PHO84的表达获得积极的反馈。删除负责上游SPL2转录的区域后，几乎所有细胞都表达SPL2。这些结果表明，PHO84和SPL2表达的细胞间差异取决于SPL2启动子的特定部分，并受Bmh1和Spl2的控制。