Multiple Transcriptional Variants and RNA Editing inC18orf1,a Novel Gene with LDLRA and Transmembrane Domains on 18p11.2

Abstract

C18orf1is a novel brain-expressed transcript, mapping to 18p11.2. Upon further characterization, we found multiple and differentially expressed transcriptional variants.C18orf1α1, an 8.5-kb transcript, was predicted to code for a 306-amino-acid protein and a 7.1-kb 3′-untranslated region (UTR). This variant was encoded by at least six exons. Alternative transcripts included α2, identical to α1 but missing 18 residues, and N-terminal-truncated variants termed β1 and β2. A motif search suggested the presence of a transmembrane domain in both α and β and a low-density lipoprotein receptor class A (LDLRA) domain in the α-specific N-terminal. In LDLR, LDLRA has been shown to be involved in binding Ca2+and LDL, raising the possibility thatC18orf1might bind Ca2+and an unknown ligand. We also present evidence of RNA editing in the 5′-UTR of β2, the first demonstration of this phenomenon in 5′-UTR.