This study evaluates the repression activities of two DUF3669-containing KRAB-ZNF proteins; ZNF746 and ZNF777 in addition to the oligomerizing ability of their domain of unknown function (DUF3669). A new domain model for DUF3669 has been established in this study. DUF3669 as an oligomerizing domain was confirmed in our study. Our data revealed the adding functionalities for the repression activities of ZNF746; DUF3669 as an oligomerizing domain might recruit other DUF3669-KRAB-ZNF proteins and the SUMOylation might stabilize the repression complex and directly recruit chromatin modifiers.