Relative levels and structural characteristics of prothrombin mRNAs prepared from the liver of a prothrombin 20210G/A heterozygote.

(A) Levels of prothrombin 20210G and 20210A mRNAs in primary hepatocytes. The expected number of colonies derives from the assumption that the average 125% prothrombin levels in 20210G/A heterozygotes arise from an approximate 1.5-fold excess of 20210A mRNA. The observed number of colonies, representing the ratio of 20210G and 20210A mRNAs in the liver of a 20210G/A heterozygote, were determined using the method described in Figure 1. (B) The 20210A mutation alters the polyadenylation pattern of prothrombin mRNA. The genomic DNA sequence bracketing position 20210 of the prothrombin gene is illustrated. The wild-type prothrombin mRNA (20210G) is polyadenylated at 2 positions: the published position (20210, 26%) and a position 2 nucleotides downstream (20212, 74%). The mutant prothrombin mRNA (20210A) is polyadenylated exclusively at position 20210.