Key Points
- To determine how alternative splicing of human type 1 angiotensin II receptor (AT1) mRNA modulates translation efficiency and generates distinct receptor isoforms.
- Characterized genomic and cDNA clones of the five-exon human AT1 gene.
- Assessed translation efficiency of alternatively spliced upstream exons (exons 1–3) in cell-free translation systems and transfected mammalian cells.
- Evaluated ligand binding and downstream signaling capabilities of translated receptor isoforms.
- Exon 1 strongly repressed translation in cell-free systems due to stable RNA secondary structure but enhanced translation in transfected cells.
- Exon 2 markedly inhibited protein synthesis in both in vitro and cellular systems via an upstream minicistron initiated by an optimal start codon.
- Transcripts combining exons 3 and 5 constituted up to one-third of tissue AT1 mRNA and encoded a functional receptor isoform with a 32–35 amino acid N-terminal extension exhibiting normal binding and signaling.
Structured PICO
PPopulationIn vitro translation system and transfected cells studying human type 1 angiotensin II receptor (AT1) mRNA
IInterventionAlternative splicing of AT1 mRNA (exons 1 to 5)
OOutcomeTranslation efficiency and receptor isoform function (ligand binding and signaling properties)surrogate
Alternative splicing of the human AT1 receptor gene generates multiple mRNA species that are translated at different efficiencies and encode two distinct, functional receptor isoforms.