Isolation of the human gene for bone gla protein utilizing mouse and rat cDNA clones

cDNAs which encode bone gla protein (BGP), an abundant gamma-carboxylated protein of bone, have been cloned from rat and mouse osteosarcoma cell lines. DNA sequence analysis indicates that the cDNAs code for both the 50 (rat) or 46 (mouse) amino acids of the mature proteins and a 49 amino acid leader peptide. The leader peptide of each BGP includes the expected hydrophobic signal sequence and an apparent pro sequence. Although there is no homology between the mature forms of BGP and the gamma-carboxylated clotting factors, we note that there is some homology between their leader peptides. These cDNAs have been used to examine the modulation of BGP mRNA levels by osteoblastic cells in response to hormones. The cDNAs have also allowed isolation of the human BGP gene; analysis of this gene indicates the presence of four exons. Comparison of the exon structure of the BGP gene and the Factor IX (a gamma-carboxylated clotting factor) gene suggests that the exons encoding the part of the leader peptides presumably directing gamma-carboxylation arose from a common ancestral sequence.