Creation of the two isoforms of rodent NKG2D was driven by a B1 retrotransposon insertion.
The mouse gene for the natural killer (NK) cell-activating receptor Nkg2d produces two protein isoforms, NKG2D-S and NKG2D-L, which differ by 13 amino acids at the N-terminus and have different signalling capabilities. These two isoforms are produced through differential splicing, but their regulation has not been investigated. In this study, we show that rat Nkg2d has the same splicing pattern as that of the mouse, and we mapped transcriptional start sites in both species. We found that the splice forms arise from alternative promoters and that the NKG2D-L promoter is derived from a rodent B1 retrotransposon that inserted before mouse-rat divergence. This B1 insertion is associated with loss of a nearby splice acceptor site that subsequently allowed creation of the short NKG2D isoform found in mouse but not human. Transient reporter assays indicate that the B1 element is a strong promoter with no inherent lymphoid tissue-specificity. We have also identified different binding sites for the ETS family member GABP within both the mouse and rat B1 elements that are necessary for high-promoter activity and for full Nkg2d-L expression. These findings demonstrate that a retroelement insertion has led to gene-regulatory change and functional diversification of rodent NKG2D.
Lai
C Benjamin
CB
Department of Medical Genetics, Terry Fox Laboratory, British Columbia Cancer Agency, University of British Columbia, Vancouver, BC, Canada.
Zhang
Ying
Y
Rogers
Sally L
SL
Mager
Dixie L
DL
D017398:Alternative Splicing; D000818:Animals; D001483:Base Sequence; D001665:Binding Sites; D002460:Cell Line; D004257:DNA Polymerase II / Q000378:metabolism; D004742:Enhancer Elements, Genetic; D005091:Exons; D051268:GA-Binding Protein Transcription Factor / Q000378:metabolism; D006801:Humans; D051379:Mice; D008810:Mice, Inbred C57BL; D008969:Molecular Sequence Data; D055655:NK Cell Lectin-Like Receptor Subfamily K / Q000235:genetics* / Q000378:metabolism; D011401:Promoter Regions, Genetic; D020033:Protein Isoforms / Q000235:genetics / Q000378:metabolism; D051381:Rats; D020086:Short Interspersed Nucleotide Elements; D024363:Transcription Initiation Site
D051268:GA-Binding Protein Transcription Factor; C527086:Klrk1 protein, mouse; D055655:NK Cell Lectin-Like Receptor Subfamily K; D020033:Protein Isoforms; D004257:DNA Polymerase II