The intronic prothrombin 19911A>G polymorphism influences splicing efficiency and modulates effects of the 20210G>A polymorphism on mRNA amount and expression in a stable reporter gene assay system.
The common prothrombin gene cleavage site mutation 20210G>A is associated with elevated prothrombin levels and thrombosis. The pathomechanism of the 20210G>A mutation was explained by increased mRNA formation and/or more efficient translation. Human studies also showed an influence of the intronic 19911A>G polymorphism on prothrombin activity. We established HepG2 cell lines stably transfected with prothrombin mini-genes containing the last 2 prothrombin exons, the last intron, 3' untranslated region (UTR), and flanking sequence. The highest mRNA expression and protein activity resulted from the mutant haplotype 19911A-20210A. Haplotypes with wild-type cleavage site (19911A-20210G, 19911G-20210G) also differed significantly as a consequence of the intronic 19911 mutation; the 19911G-20210G haplotype showed lower expression than the 19911A-20210G haplotype, whereas previous clinical studies have reported elevated prothrombin activity with the 19911G-20210G haplotype. The cleavage site pattern was homogeneous with 20210A, which may cause a favorable intracellular processing, and heterogeneous with 20210G. In an independent assay for splicing efficiency, 19911G showed about 30% higher efficiency than 19911A. We conclude that the intronic 19911A>G single nucleotide polymorphism is itself functional and changes splicing efficiency by altering a known functional pentamer motif. Further studies are needed to define the value of additional prothrombin 19911 genotyping for thrombophilia screening, especially in cases heterozygous for 20210G>A.
D017398:Alternative Splicing; D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D002460:Cell Line; D018389:Codon, Nonsense / Q000235:genetics; D017931:DNA Primers; D004797:Enzyme-Linked Immunosorbent Assay; D017930:Genes, Reporter; D014644:Genetic Variation; D006801:Humans; D007438:Introns / Q000235:genetics*; D010446:Peptide Fragments / Q000737:chemistry; D020641:Polymorphism, Single Nucleotide; D011516:Prothrombin / Q000737:chemistry / Q000235:genetics*; D012333:RNA, Messenger / Q000235:genetics*; D015183:Restriction Mapping; D019851:Thrombophilia / Q000235:genetics; D014158:Transcription, Genetic / Q000235:genetics*; D014162:Transfection
D018389:Codon, Nonsense; D017931:DNA Primers; D010446:Peptide Fragments; D012333:RNA, Messenger; D011516:Prothrombin