ATP-dependent DNA helicase that plays a role in formation, organization, stability and heritability of heterochromatin and thus regulates several physiological traits. Binds to the nucleosome and promotes chromatin remodeling in an ATP-dependent manner; induces nucleosome repositioning on a short DNA fragment, and, possibly, could be guided to target sites (including silent transposable elements) by small interfering RNAs (siRNAs). Can bind both free and nucleosomal DNA. Required for the heritable maintenance of genome integrity and transcriptional gene silencing (TGS), including homology-dependent gene silencing (HDG silencing), via the maintenance of DNA methylation (mostly on cytosine, in both CpG and CpHpG sites, where H is A, T or C) and of histone methylation (e.g. chromatin methylation). May facilitate localization of MBD proteins at specific nuclear domains. Necessary for the maintenance of the genomic imprint at the MEA locus, especially for the silencing of paternally inherited MEA locus. Plays a major role in the inactivation maintenance of retrotransposons (e.g. Tar17, SINE, LINE, ATLN39, CAC1 (CACTAs), Athila elements, and mutator-like elements MULEs and TIR-MULEs) and the silencing of repeated genes and transgenes (e.g. T-DNA insertions). Required for KYP-dependent histone H3 'Lys-9' (H3K9me) methylation, deacetylation of histone H4 'Lys-16' (H4K16) and MET1-dependent DNA methylation. Involved in the chromatin organization of 5S rRNA genes (localized in the pericentromeric heterochromatin of chromosomes 3, 4, and 5) modifications during heterochromatin establishment. Prevents siRNA accumulation (siRNA are probably involved in epigenetic inheritance and in 5S rRNA genes regulation by silencing). Required during plant organogenesis and development, as well as during seed formation. ATP + H2O = ADP + H(+) + phosphate ATPase activity is stimulated 3-fold by DNA (both free and nucleosomal) binding. All results where obtained at pH 8.0 and 25 degrees Celsius. Interacts with the MBD domains of MBD2, MBD5 and MBD6. Closely associated with pericentric heterochromatin. Reactivated transcription of heavily methylated silent loci, via chromatin demethylation. Hypomethylated chromatin; gain of histone H3 'Lys-4' methylation (H3K4me) but depletion of histone H3 'Lys-9' methylation (H3K9me). Altered leaf shape, increased cauline leaf number, and delayed flowering onset (due to FWA derepression). Accumulates developmental abnormalities and transcription derepression by slowly inducing heritable lesions (hopymethylation) at unlinked loci. Derepressed paternally inherited MEA locus in male gametophytes and seeds. Reactivation of several silent retrotransposons. Smaller chromocenters with reduced heterochromatin amount. Causes a striking decondensation of centromeric heterochromatin, a redistribution of the remaining methylation of DNA, and a drastic change in the pattern of histone modification. Abnormal subcellular localization of MBD proteins (e.g. MBD2, MBD5, MBD6 and MBD7). Smaller seeds in male inherited disruption, but larger seeds in female inherited ones. The heritable and cumulative hypermethylation and silencing of BNS, leading to the bonsai phenotype, requires the hypomethylation of the flanking LINE transposon. Belongs to the SNF2/RAD54 helicase family.