This is the tudor domain found in DNA repair protein crb2. Structural and functional studies of Crb2 and its mammalian homologue 53BP1 indicate that the conserved tandem-Tudor domain of 53BP1 and Crb2 preferentially interacts with H4K20me2, though it also binds to H4K20me1 [1]. Furthermore, despite low amino acid sequence similarity, Crb2 is structurally related to 53BP1 in having two tudor domains and a conserved dimethyllysine-binding pocket, and that, like 53BP1, it directly binds H4-K20me2 [2].

1: Tudor: a versatile family of histone methylation 'readers'. Lu R, Wang GG; Trends Biochem Sci. 2013;38:546-555. PMID:24035451

2: Structural basis for the methylation state-specific recognition of histone H4-K20 by 53BP1 and Crb2 in DNA repair. Botuyan MV, Lee J, Ward IM, Kim JE, Thompson JR, Chen J, Mer G; Cell. 2006;127:1361-1373. PMID:17190600