Biosynthesis and postsynthetic processing of human C-reactive protein.

Human C-reactive protein (CRP) is one of several plasma proteins that increase after tissue injury or inflammation. The magnitude of the increase in CRP (100 to 1000-fold over the resting state) makes this an excellent model for studies of eukaryotic gene control. Accordingly, the biosynthesis and postsynthetic processing of human CRP was examined under cellfree conditions and in Xenopus oocytes injected with liver mRNA. The primary translation product is larger than native serum CRP by an 18-amino acid amino terminal extension. The sequence of this signal peptide was derived from nucleotide sequencing of a 1.8-kilobase (Kb) CRP-specific cDNA clone. Northern blot analysis revealed a CRP mRNA of approximately 2.2 Kb, a size more than three times that required (615 bases) to code for the primary translation product. These data form the basis for study of molecular control of the acute phase response.