Homo sapiens mgU12-22/U4-8 scaRNA. This scaRNA was characterized by Tycowski et al. (2004). It is composed of two C/D box domains that are predicted to guide the 2'O-ribose methylation of U12 snRNA G22 and U4 snRNA C8. The 3' C/D box domain was previously cloned by Darzacq et al. (2002) and named U91 (see this entry). Northern blot analysis of RNAs from HeLa cells revealed the presence of the full length mgU12-22/U4-8, as well as U91 (Tycowski et al., 2004). Cell fractionation experiments localized mgU12-22/U4-8 in the nucleoplamic fraction (in agreement with a localization in Cajal bodies), but U91 in the nucleolar fraction. From its genomic localization, mgU12-22/U4-8 is transcribed from an independent unit. In agreement, a significant fraction bears a trimethylguanosine cap.