Feucht A, Magnin T, Yudkin M D, Errington J
Sir William Dunn School of Pathology, University of Oxford, England, UK.
Genes Dev. 1996 Apr 1;10(7):794-803. doi: 10.1101/gad.10.7.794.
During sporulation in Bacillus subtilis an asymmetric cell division gives rise to unequal progeny called the prepore and the mother cell. Gene expression in the prespore is initiated by cell-specific activation of the transcription factor sigma(F). Three proteins participate in the regulation of sigma(F) activity. The first, SpoIIAB, is an inhibitor of sigma(F), that is, an anti-sigma factor. SpoIIAB is also a protein kinase that catalyzes phosphorylation of the second regulatory protein SpoIIAA (the anti-anti-sigma factor), and thus inactivates it. A third protein, SpoIIE, was shown recently to be able to dephosphorylate SpoIIAA-P in vitro. Here we show that SpoIIE is a bifunctional protein with two critical roles in the establishment of cell fate. First, we confirm by the use of in vivo experiments that it regulates the release of sigma(F) activity by dephosphorylating SpoIIAA-P. Second, we show that SpoIIE is needed for normal formation of the asymmetric septum that separates the prespore from the mother cell. Combination of these two functions in a single polypeptide may serve to couple the release of the cell-specific transcription factors with the formation of the differentiating cells.
在枯草芽孢杆菌的芽孢形成过程中，不对称细胞分裂产生了不相等的子代，即前芽孢和母细胞。前芽孢中的基因表达是由转录因子σ(F)的细胞特异性激活引发的。三种蛋白质参与了σ(F)活性的调节。第一种是SpoIIAB，它是σ(F)的抑制剂，即一种抗σ因子。SpoIIAB也是一种蛋白激酶，可催化第二种调节蛋白SpoIIAA（抗抗σ因子）的磷酸化，从而使其失活。最近发现第三种蛋白质SpoIIE能够在体外使SpoIIAA-P去磷酸化。在此我们表明，SpoIIE是一种双功能蛋白，在细胞命运确立过程中具有两个关键作用。首先，我们通过体内实验证实，它通过使SpoIIAA-P去磷酸化来调节σ(F)活性的释放。其次，我们表明SpoIIE是正常形成将前芽孢与母细胞分隔开的不对称隔膜所必需的。单一多肽中这两种功能的结合可能有助于将细胞特异性转录因子的释放与分化细胞的形成联系起来。
