Figure 5.

Potential interactions between the 5′-terminal region of U1 snRNA and the 5′-splice sites of the three fibrillarin pre-mRNA introns and between the 5′-terminal region of U1 snRNA and the 5′-splice site of the SL RNA (17, 18). The cap at the 5′-end of U1 snRNA is not shown. The exon–intron boundaries are indicated by a slash (/), with the conserved GU at the 5′-end of each intron underlined.