Fig. 8. Summary and proposed model. (A) Summary of PAL-1 (red) and MEX-3 (green) localization data. (B) Working model for regulation of PAL-1 expression. Anteriorly localized PAR-3 (blue) restricts cortical PAR-1(orange) to the posterior. par-1 then restricts MEX-5 and MEX-6 (purple) to the anterior. mex-5 and mex-6 protect MEX-3 from degradation in the anterior, enabling the continued repression of PAL-1. In the absence of mex-5 and mex-6 in the posterior, par-4 inactivates MEX-3 (*), and subjects it to rapid spn-4-dependent degradation. In the absence of spn-4, inactive MEX-3 can interfere with active MEX-3, resulting in ectopic PAL-1 expression.