The human protein S locus: Identification of the PSα gene as a site of liver protein S messenger RNA synthesis

The protein S locus, situated on chromosome 3, consists of two protein S genes. Here, we report the cloning and complete nucleotide sequence of the 3′-untranslated region of the two genes designated PSα and PSβ. Both regions span approximately 1,200 nucleotides. They show a high degree (-97%) of homology, with deviations caused by small deletions, insertions and point mutations. Comparison of PSα and PSβ with the reported protein S liver cDNAs, shows that the latter all originate from the PSα gene. The PSα gene therefore is marked as the major site of synthesis of liver protein S mRNA. Sequence comparison with the bovine protein S cDNA reveals that the PSβ gene has accumulated a few more mutations than the PSα gene since duplication of the ancestral protein S gene that seems to have occurred recently during primate evolution.