Fig. 7. Puf proteins nucleate the assembly of different repressor complexes in Drosophila and budding yeast. Models of the mechanism by which Pum and MPT5 repress CycB and HO mRNAs in Drosophila and S. cerevisiae, respectively. The data of Figs 2 and 4 are consistent with the idea that a germline-limited co-factor (magenta) binds directly to the CycB NRE; however, other roles for the co-factor are possible.