Skip to main content
. 2014 Mar 26;3(2):243–254. doi: 10.3390/biology3020243

Figure 1.

Figure 1

A model for the involvement of splicing factors in different steps of the RNA-directed DNA methylation (RdDM) pathway. With the assistance of CLSY1, Pol IV is recruited to transcribe transposons and repeat loci through an interaction with DTF1/SHH1, which recognizes unmethylated K4 and methylated K9 modifications of histone H3. Coupling of Pol IV and RNA-DEPENDENT RNA POLYMERASE2 (RDR2) is required for copying Pol IV-generated transcripts into dsRNAs by RDR2. The splicing factor SR45 might be recruited by the Pol IV-RDR2 complex and facilitates the siRNA generation. The dsRNAs were diced into 24-nt siRNAs by DICER-LIKE 3 (DCL3), followed by HEN1 methylating the siRNAs at their 3'ends. One strand of the siRNAs is loaded into AGO4 and the siRNA‑bound AGO4 is recruited by Pol V transcript through base-pairing between the siRNA and nascent transcript. The interaction of AGO4 with KTF1 and Pol V is required for the stable association of AGO4 with the Pol V transcripts. DDR complex, which is consisted of DRD1, DMS3 and RDM1 proteins, facilitates Pol V transcription. The interaction of RDM1 with AGO4 and DRM2 may be involved in recruiting DRM2 to Pol V-target loci for catalyzing DNA methylation. The splicing factors STA1 and ZOP1 might be recruited by AGO4-containing effector complex, Pol V or Pol V transcripts and act at a late step in RdDM, while the splicing factor RDM16 might be simply recruited by Pol V or Pol V transcripts to function in RdDM.