FIGURE 4.

Sequence and putative secondary structure of S. cerevisiae U6, human U6, and U6atac. The secondary structure of U6 from S. cerevisiae (left) is based on the structure of the U6 snRNP core (Montemayor et al. 2014), and includes the 5′SL, telestem, asymmetric bulge, ISL, and 3′ tail. The secondary structure of human U6 and U6atac within the U6 snRNP has not been experimentally determined, and is shown with secondary structure to mimic that of yeast U6. Human U6 contains a 5′SL, the ISL, and 3′ tail, and may contain an asymmetric bulge and telestem region. U6atac lacks a 5′SL but contains an additional 3′SL. Constitutively modified nucleotides are highlighted in red. Residues involved in base triples in the catalytic spliceosome (U2/U6.U5) are boxed in red.