Fig. 8: Model of P granule assembly and mRNA repression.

a P granules assemble at the nuclear pore with assembly-competent PGL-1 protein. PGL-1 is shown as a dimer for simplicity but multivalent PGL-1s likely form an oligomeric protein–RNA network via its N-terminal dimerization domain (NtDD, yellow) and central dimerization domain (CDD, orange). WAGO-1 (blue) binds to RNA (purple), as expected for an Argonaute, and WAGO-1-associated RNAs are repressed, potentially by mRNA turnover (purple). b When PGL-1 NtDD cannot dimerize, PGL-1 fails to properly assemble into P granules at the nuclear periphery. WAGO-1 assembles independently into P granules. PGL-1-associated, non-granular mRNAs (green) are available for translation (ribosomes, black). c In the absence of cytoplasmic Argonaute WAGO-1, PGL-1 proteins assemble into P granules normally with its associated mRNA (purple), but loss of WAGO-1 perturbs repression of P granule-localized transcripts. PGL-1’s liquid droplet properties permit diffusion of some transcripts (green) into the cytoplasm for translation. See text for further discussion.