Fig 9.

Role of SmD3 in snoRNA production. A model for the SmD3 role in snoRNA production is shown. The open boxes represent exons, the black lines represent intronic sequences, and snoRNA sequences are shown in yellow and blue. The colored circles represent snRNPs. In the presence of wild-type levels of SmD3, the complement of snRNAs is sufficient to support splicing of pre-mRNAs into mature mRNAs and intron lariats that are sufficiently long-lived to produce snoRNAs. While haploinsufficiency of SmD3 is able to support wild-type levels of mRNA production from splicing, associated decreases in the abundance of the of U4 and U5 snRNPs results in decreased intron lariat abundance and decreased levels of intronic snoRNAs.