Figure 2. The kinetic model for PB formation.
Model illustrating the hypothesis that the extent of PB formation is directly proportional to the cytoplasmic levels of repressed mRNPs and depends on competing rates of translational repression, PB factor recruitment, mRNP multimerization and mRNA decay. Before mRNAs can assemble into PBs, they must be translationally repressed. Translational silencing factors then promote the formation of a PB “monomer” by recruiting decapping factors and/or other PB assembly components. If mRNA decay enzymes are not limiting and thus mRNA decay is rapid, mRNAs may be degraded prior to PB assembly. However, if decay enzymes are limiting, the repressed mRNAs assemble into PBs where they can be degraded, or released back into the translational pool.