This domain is found in Hit1 protein (Hit1p) present in Saccharomyces cerevisiae. Hit1p contributes to C/D small nucleolar RNPs (snoRNPs) stability and pre-RNA maturation kinetics by associating with U3 snoRNA precursors and influencing its 3'-end processing. Snu13p-Rsa1p-Hit1p heterotrimer binds C/D snoRNAs. C/D snoRNAs are essential for the biogenesis of ribosomes and spliceosomes. The domain adopts a Pac-Hit fold that forms a claw which locks the alpha-1 helix of Rsa1p, while the Rsa1p alpha-2 helix packs against the exposed surface of the Hit1p Pac-Hit domain alpha-3 helix [1].

1: Protein Hit1, a novel box C/D snoRNP assembly factor, controls cellular concentration of the scaffolding protein Rsa1 by direct interaction. Rothe B, Saliou JM, Quinternet M, Back R, Tiotiu D, Jacquemin C, Loegler C, Schlotter F, Pena V, Eckert K, Morera S, Dorsselaer AV, Branlant C, Massenet S, Sanglier-Cianferani S, Manival X, Charpentier B; Nucleic Acids Res. 2014;42:10731-10747. PMID:25170085