FIG. 3.

A minimal 5′ hairpin stem is sufficient for accumulation of hTR and snoRNAs. Total RNA from transfected 293T cells was examined by blot hybridization. At left are shown secondary structures of the hTR H/ACA domain phylogenetic model (A), the human snoRNA U64 (B), and the human snoRNA ACA28 (C). Positions of internal deletion are indicated: Δ1, deletion of H/ACA motif upper stem; Δ2, deletion of the upper stem and pocket; Δ3, deletion of the entire stem/pocket/stem hairpin. Only hTR Δ2 and the snoRNA 5′ stem cap (SC) deletions insert a GAAA tetraloop in place of the deleted sequence. Human snoRNA pocket sequences are highlighted in bold. L del, R del, L+R del indicate deletion of the left, right, or combined left and right sides of the pocket, respectively.