SigF Onset of sporulation – (Stage I - II)
SigF during the onset of sporulation
The sigF gene is part of the tricistronic spoIIA operon, together with spoIIAA and spoIIAB. Just prior to formation of an asymmetric septum, the operon is transcribed under the control of Spo0A~P and σH. Because of the presence of two identical copies of the chromosome in both compartments of the sporulating cell, sigF transcript is present both in the mother cell and in the forespore. However, posttranslational modification involving SpoIIAA, SpoIIAB and SpoIIE ensures that σF remains inactive until after asymmetric division is complete 76. Direct binding of SpoIIAB to σF inactivates the sigma factor, while SpoIIAB kinase activity simultaneously phosphorylates and hence inactivates its antagonist SpoIIAA 77, 78.