Impact of untranslated regions (UTRs) on differential translation among SftpA1 and SftpA2 gene variants

Abstract

Surfactant protein A (SP‐A) plays an important role in host defense and surfactant‐related functions. In humans, SP‐A is encoded by two genes (SftpA1, SftpA2). Structural and functional differences between SftpA1 (SP‐A1) and SftpA2 (SP‐A2) products have been observed; as well as splice and sequence variation, respectively, at the 5′UTR and 3′UTR. Here, we studied the role of SP‐A 5′UTR and 3′UTR variants, and polyA on translation. We generated constructs (n=14) with the luciferase reporter gene flanked by SPA 5′UTR (SP‐A1: AD′; SP‐A2: ABD, ABD′) and/or 3′UTR (SP‐A1: 6A2, 6A4; SP‐A2: 1A0, 1A3). mRNA was obtained in vitro and polyA was added or omitted. NCI‐H441 cells were transfected and luciferase activity was measured.Results1) in the absence of 3′UTR, the SP‐A 5′UTRs exhibit an additive effect with polyA and stimulate translation with different efficiencies (ABD=ABD′>AD′> no 5′UTR); 2) in the absence of 5′UTR, 3′UTR increased translation; with no differences among variants; 3) the combination of SP‐A 5′UTR and 3′UTR showed an additive effect on translation. In this context, the SP‐A1 6A4 3′UTR variant showed higher translation than 6A2, whereas no differences were observed between SP‐A2 3′UTRs (1A0, 1A3).ConclusionThe 5′UTR, 3′UTR, and polyA contribute to the differential translation of SP‐A1 and SP‐A2. However, the SP‐A1 3′UTR appears to regulate variant‐specific translation. (Supported: NIH HL‐34788)