Structure and function of echinoderm telomerase RNA

The vertebrate TR H/ACA domain is conserved throughout echinoderm TRs. Comparison of representative TR H/ACA domains from vertebrate, human (A); sea urchin, purple sea urchin (B); brittle star, blunt spined brittle star (C); and feather star, Japanese feather star (D). The namesake box H and ACA moieties (open boxes) are present in echinoderm TRs with the full-length 3′-end identified. The CAB box (open box) is present in sea urchin and brittle star TRs. The CAB box is either lost or cryptic in teleost fish and feather star TRs. Covariation (black bar), universal-invariant between vertebrates and echinoderm (red), and group-invariant (orange) nucleotides for vertebrate, sea urchin, and brittle star TR H/ACA domains is based on multiple sequence alignment of 42 vertebrate (Chen et al. 2000; Podlevsky et al. 2008; Xie et al. 2008), 9 sea urchin/sand dollar, 3 brittle star, and a feather star species (see Supplemental Fig. S5).