Splicing of effector cell protease receptor-1 mRNA is modulated by an unusual retained intron.
Effector cell protease receptor-1 (EPR-1) is a transmembrane glycoprotein receptor for factor Xa that contributes to cell surface assembly of proteolytic activities and leukocyte mitogenesis. It is now shown that membrane expression of EPR-1 is dynamically modulated by mRNA splicing. Northern hybridization analysis of EPR-1-expressing cells and genetically engineered transfectants demonstrates that this mechanism involves removal of a 451 bp intervening sequence retained in 70-90% of mature mRNA, as quantitated by polymerase chain reaction amplification and ribonuclease protection studies. Splicing of the intervening sequence occurs in a cell type-specific fashion, as judged by the constitutive membrane overexpression of EPR-1 in certain leukemic B lymphocytes and monocytic cells. Furthermore, phenotypic analysis of cell lines stably transfected with functionally spliced or unspliced EPR-1 constructs suggests a potential role of intron cis-acting sequence(s) in splicing regulation. Instead of a transmembrane receptor for factor Xa (EPR-1a), the most prevalent unspliced EPR-1 transcript generates a novel truncated protein of 110 amino acids (EPR-1b), in which a unique intron-encoded -COOH terminus carries a potential nuclear targeting signal PPQHRAKS. An antibody generated against the intron-encoded sequence of EPR-1b demonstrates prominent nuclear localization of this variant isoform in indirect immunofluorescence staining of permeabilized cells. These findings provide evidence for a novel mechanism based on high efficiency intron retention modulating factor Xa-dependent cellular effector functions.
Altieri
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DC
Department of Vascular Biology, Scripps Research Institute, La Jolla, California 92037.
D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D016466:CHO Cells; D002478:Cells, Cultured; D006224:Cricetinae; D018076:DNA, Complementary; D006801:Humans; D051034:Inhibitor of Apoptosis Proteins; D007438:Introns; D008969:Molecular Sequence Data; D012326:RNA Splicing; D011956:Receptors, Cell Surface / Q000235:genetics*; D012697:Serine Endopeptidases / Q000235:genetics*; D000077022:Survivin; D014162:Transfection
C107489:BIRC5 protein, human; D018076:DNA, Complementary; D051034:Inhibitor of Apoptosis Proteins; D011956:Receptors, Cell Surface; D000077022:Survivin; D012697:Serine Endopeptidases