3TIX:
reference: The Chp1-Tas3 core is a multifunctional platform critical for gene silencing by RITS., Schalch T, Job G, Shanker S, Partridge JF, Joshua-Tor L, Nat Struct Mol Biol. 2011 Nov 13;18(12):1351-7. doi: 10.1038/nsmb.2151. PMID: 22081013

This OCA Structure page
uses Jmol, developed by the Jmol Development Team (documentation).