InterPro domain: IPR039276

This entry includes SAWADEE HOMEODOMAIN HOMOLOGS 1 and 2 (SHH1 and SHH2) from plants. In Arabidopsis, SHH1 is a homeodomain protein required for DNA methylation and for the accumulation of siRNAs at specific loci [ 1 ]. It interacts with Pol-IV and acts upstream in the RdDM (RNA-directed DNA methylation) pathway. Its SAWADEE domain is a chromatin-binding module that functions as a dual lysine reader, probing for both unmethylated K4 and methylated K9 modifications on the histone 3 (H3) tail [ 2 ]. The function of SHH2 is not clear.

1. SHH1, a homeodomain protein required for DNA methylation, as well as RDR2, RDM4, and chromatin remodeling factors, associate with RNA polymerase IV. PLoS Genet.
2. Polymerase IV occupancy at RNA-directed DNA methylation sites requires SHH1. Nature 7, e1002195