Functional Requirement for Arginine Methylation of the Dicer Helicase Domain in 26G Endo-siRNA Pathway Activity and the Oocyte Meiotic Program

Here, we identify regulatory roles for a non-traditional glycine-arginine-rich (GAR) motif, GRARR, in motif VI of the helicase domain. Mutations to conserved arginine residues of the GRARR motif impair maternal 26G endo-siRNA production and disrupt oocyte-to-embryo transition.

We show that asymmetric di-methylation of Dicer R495 within this motif facilitates binding to ERI-5, a tandem-Tudor protein within the ERI Complex, likely potentiating 26G siRNA biogenesis, as deletion of eri-5 Tudor domains phenocopies Dicer GRARR mutants. Notably, these phenotypes are similar to those observed in Dicer phosphorylation mutants, implicating both arginine methylation and serine phosphorylation function in a coordinated mechanism.