Fig. 8: The E granule promotes specialized synthesis of 5’ siRNAs.

a Normalized 22G RNA read distribution across E-class siRNAs targeting cls-2 and klp-7. Additional examples of 22 G RNAs covering E-class genes can be found in Supplementary Fig. 17a. b Metaprofile analysis showing the distribution of normalized 22G RNA (sRNA-seq) reads (RPM) along E-class genes in the indicated animals. EGC-1 and ELLI-1 are exclusively required for the production of 5’ E-class siRNAs. c Normalized 22G RNA read distribution across E-class siRNA-targeted genes cls-2 and klp-7. d Metaprofile analysis showing the distribution of normalized 22G RNA (sRNA-seq) reads (RPM) along E-class genes in the indicated animals. e A working model for the role of germ granule compartmentation in siRNA generation and AGO/siRNA function. E granules and Mutator foci are two independent subcompartments of perinuclear germ granules for 22G RNAs generation using a largely nonoverlapping set of RNA transcripts as templates. E granules-derived 22G RNAs are bound to CSR-1, while 22G RNAs derived from Mutator foci are bound to WAGO-1 and HRDE-1. WAGO-4 binds to siRNAs derived from the exogenous RNAi treatment and promotes transgenerational inheritance^22,91. It is currently unknown whether these siRNAs are produced by the Mutator complex in Mutator foci or by EGO-1 in E granules. 22G RNAs mapping to the 3’ regions of E-class mRNAs are likely produced by the EGO module in the cytosol. Different AGO/siRNAs complexes localize to distinct intracellular subcompartments of the germ granule. Germline P-bodies were reported to be located on top of P granules⁸⁴. The relative sizes of different subcompartments of germ granules are not yet known.