Transposase-derived protein that may have nuclease activity (Probable). Antagonist of polycomb-group (PcG) protein-mediated chromatin silencing, probably by preventing the association of POLYCOMB REPRESSIVE COMPLEX 2 (PRC2) with its accessory components. Needed for full reactivation of several floral homeotic genes that are repressed by PcG (PubMed:26642436). Interacts with core components of POLYCOMB REPRESSIVE COMPLEX 2 (PRC2), a PcG protein complex with H3K27me3 histone methyltransferase activity. Associates with plant-specific PRC2 accessory components such as MSI1, EMF2, VRN2, FIE and CLF. Expressed in roots, inflorescence stems, seedlings, leaves, flower buds, inflorescences, and siliques. Suppression of PcG defects in several PRC1 and PRC2 components including lhp1 (in alp1-2 and alp1-3 mutants) and clf (in alp1-3 and alp1-4 mutants) phenotypes (PubMed:26642436, PubMed:22837357). In alp1-4, weak downward curling and slightly late flowering in short days. Increases synergistically ult1 and ult2 floral organ defects in double mutants alp1-3 ult1 and alp1-3 ult2. The double mutant alp1-3 efs has a stronger dwarf, branched phenotype than efs single mutant (PubMed:26642436). Belongs to the HARBI1 family.