Subunit of the chromatin-remodeling complex (DDR complex) that mediates RNA polymerases IV and V (Pol IV and Pol V) recruitment to chromatin (PubMed:19013275, PubMed:22864289). Cooperates with Pol IV and Pol V to regulates RNA- and RNAi- (RNA interference) directed non-CpG de novo DNA methylation on cytosine of genes targeted for silencing and enhancers, also known as siRNA-directed DNA methylation (RdDM), thus leading to epigenetic modification of the genome and promoting/maintaining heterochromatin (PubMed:15120073, PubMed:15947783, PubMed:15924141, PubMed:16724114, PubMed:16741558, PubMed:19204117, PubMed:19825647, PubMed:22647529, PubMed:18425128). In collaboration with Pol V, mediates/maintains, in cis, methylation-associated self-silencing of exogenous transgene transcribing inverted-repeat (exo-IR) silencer (exo-Pdsi) to restrain exo-IR dsRNA accumulation and subsequent inappropriate silencing of active protein-coding genes (e.g. PDS) by exo-IR-derivating 24-nt siRNAs (PubMed:21771120). Also required to mediate loss of CpG methylation when the silencing inducer is withdrawn (PubMed:15947783). Required for the maintenance of retrotransposon large terminal repeats (LTRs) and transposable elements (TE) edges silencing mediated by cytosine methylation (PubMed:16724114, PubMed:23540698). Required for transcriptional repression of specific classes of pericentromeric 180-bp repeats by promoting condensation and histone H3 lysine 9 dimethylation (H3K9me2) at chromocenters (PubMed:19825650). Required for basal resistance against the necrotrophic fungal pathogen Plectosphaerella cucumerina (PubMed:22242006). Part of the chromatin-remodeling complex (DDR complex) that contains at least DRD1, DMS3 and RDM1. The DDR complex recruits/activates the RNA polymerases V and acts during siRNA-directed DNA methylation (RdDM) (PubMed:20409711, PubMed:22864289). Interacts with SUVH2 (PubMed:24463519, PubMed:24465213). Excluded from the nucleolus. Colocalizes with endogenous repeat loci. Reduced association of NRPE1 with chromatin, leading to altered chromatin binding of the DDR complex (PubMed:19013275, PubMed:22864289). Defective in RNA-directed non-CpG DNA methylation resulting in reactivation of silenced genes and enhancers, whereas methylation of centromeric and rDNA repeats is unaffected (PubMed:15120073, PubMed:15947783, PubMed:15924141, PubMed:16741558, PubMed:19825647, PubMed:18425128). Reduced accumulation of 24-nt siRNAs and reduced DNA methylation of siRNA-directed DNA methylation (RdDM) target loci (PubMed:19204117, PubMed:22647529). Increase in CpG DNA methylation leading to abnormal maintenance of some silenced genes (PubMed:15947783). Derepression of solo retrotransposon large terminal repeats (LTRs) and of transposable elements (TE) edges accompanied by reduced cytosine methylation and transcriptional up-regulation of neighboring sequences, and associated with euchromatic histone modifications but little or no H3K9 dimethylation. By contrast, LTRs of retrotransposons that remain silent in disrupted plants despite reduced cytosine methylation lack euchromatic marks and have H3K9 dimethylation (PubMed:16724114, PubMed:23540698). Decondensation of the major pericentromeric repeats and depletion of the heterochromatic mark histone H3 lysine 9 dimethylation (H3K9me2) at chromocenters, leading to transcriptional reactivation of specific classes of pericentromeric 180-bp repeats and reduced heterochromatin (PubMed:19825650). Relieved exo-Pdsi self-silencing resulting in accumulation of dsRNA and Pdsi-derivating 21-nt mobile siRNAs which increase non-cell-autonomous silencing of endo-PDS in neighboring cells (PubMed:21771120). Increases susceptibility to the necrotrophic fungal pathogen Plectosphaerella cucumerina (PubMed:22242006). Belongs to the helicase family.