This SM domain is found in Ataxin-2 [1].

1: Ataxin-2, global regulators of bacterial gene expression, and spliceosomal snRNP proteins share a conserved domain. Neuwald AF, Koonin EV; J Mol Med 1998;76:3-5. PMID:9462862

2: Comparative genomics and evolution of proteins involved in RNA metabolism. Anantharaman V, Koonin EV, Aravind L; Nucleic Acids Res. 2002;30:1427-1464. PMID:11917006