Alternative splice forms of MsrB1.

<p>(A) Genomic structure of mouse MsrB1. Red boxes indicate exons corresponding to the coding region, blue boxes show 3′-UTRs, and yellow boxes show the SECIS element. Top panel shows the Form 1 MsrB1 mRNA which lacked intron 4 due to the process of intronization. Bottom panel represents the ancestral form, Form 2 MsrB1 mRNA. (B) Schematic representation of 3′-UTRs of mammalian MsrB1 sequences. The stop codon is shown in orange, 3′-UTRs in green, alternatively spliced regions in blue, and SECIS elements in yellow. (C) Splice donor and acceptor sites in the 3′-UTR of MsrB1. The stop codon is shown in red. Intron-exon junctions are indicated by “∧”.