TAPBPR isoforms exhibit altered association with MHC class I.
Bottom Line: TAPBPR transcripts lacking exon 5 result in loss of the membrane proximal IgC domain and loss of ability to bind to MHC class I.This longer TAPBPR protein interacted with MHC class I but was attenuated in its ability to down-regulate surface expression of MHC class I.The abundance of these alternative transcripts in peripheral blood mononuclear cells and dendritic cells suggests an important role of TAPBPR isoforms in vivo.
Affiliation: Department of Pathology, Cambridge Institute of Medical Research, University of Cambridge, Wellcome Trust, Cambridge, UK.Show MeSH
Mentions: During the initial process of cloning TAPBPR into expression constructs, it became apparent that a number of alternative TAPBPR mRNA products existed in addition to the major TAPBPR transcript.10 We investigated the alternative transcripts using PCR, followed by cloning individual TAPBPR transcripts into the pCR®-Blunt II TOPO vector and screening colonies by sequence analysis. Using primers specific for TAPBPR exon 1 and exon 7 we amplified the major TAPBPR coding sequence, the α transcript, which was found in all cell types tested (Fig.1 and Table1). In IFN-γ-treated KG-1 cells we identified a longer TAPBPR mRNA product that we named the TAPBPR β transcript (Fig.1a). Although the TAPBPL gene is thought to be composed of seven exons,11 the TAPBPR β transcript has an additional exon after exon 6, which we refer to as exon 7a.
Affiliation: Department of Pathology, Cambridge Institute of Medical Research, University of Cambridge, Wellcome Trust, Cambridge, UK.