FIG 6.

The E. histolytica RNAi pathway involves EhAgo2-2 and its nuclear transport process. In this model, the polyP 27-nt sRNAs are probably generated using low levels of mRNA as the template (dashed arrow). EhAgo2-2 is illustrated as a green oval with its DR-motif region shown as a solid red circle. After loading of 27-nt sRNA into EhAgo2-2, the RISC is translocated into the nucleus using the DR-rich tail region as an NLS. Within the nucleus, the specific locus for TGS is determined by recognition of RISC and its guide sRNAs, which leads to locus-specific histone H3 modification (H3K27Me2 marker) for long-term silencing. The three mutants (ΔNLS-DR or ΔDR, PAZ mutant, and PIWI mutant) are shown along with their localization, sRNA binding, and functional impact. In this study, we show the localization and effects of the three EhAgo2-2 mutants and conclude that the tail of the DR-motif region is responsible for active nuclear transport, while the PAZ domain provides full protection of integrity of sRNA at the 3′ end.