Fig. 8. Regulation of EMTOC formation. The formation of the EMTOC requires the activity of both the SIN and APC/C. It can also be induced by overexpression of plo1⁺ but not by activation of the SIN. These observations and data from other studies, such as the ability of Plo1 overexpression to activate the SIN, would be consistent with Plo1 acting upstream of both the APC/C and the SIN (red – for details see text) (A). We favour this model over the alternative possibilities (B) that Plo1 acts independently of both of these pathways (yellow) or functions downstream of either SIN or APC (blue).