IRTA family mRNAs have a conserved structural organization.

Pattern-filled boxes represent coding domains, and thin open or shaded boxes represent UTRs. The predicted site for signal peptidase cleavage is marked by an arrowhead and was derived according to the SignalIP World Wide Web server.45 The transmembrane domain prediction algorithm is described by Tusnady et al.49 LP indicates leader peptide; Ig, immunoglobulin type; TM, transmembrane; CYT, cytoplasmic domain; A(n), polyA tail; GPI, glycosylphosphatidyl inositol. Lengths of transcripts identified by Northern blot analysis using probes indicated in the figure are shown. The various 3′ UTRs of IRTA2, which result from alternative splicing, are denoted by differential shading.