 In order to be recognized by Cdc4 of the SCF complex, Sic1 has to be phosphorylated, often by Cyclin-Cdk complexes, at least at 6 of the 9 cdk sites (Fig.2).Sic1 can also be phosphorylated by other kinases, such as Pho85-Pc11, a kinase which becomes essential when Cln1 and Cln2 are absent.