NEW ALBUMIN GENE 3' ADJACENT TO THE ALPHA(1)-FETOPROTEIN LOCUS

The albumin multigene family encodes proteins synthesized in the liver and secreted in the serum to fulfill ligand-carrier functions. The al bumin (ALB), alpha(1)-fetoprotein (AFP), and vitamin D-binding protein genes are syntenic, the ALB and AFP genes are organized in tandem, an d the AFP gene is selectively expressed in the fetal liver. We how rep ort the existence of a fourth member of the albumin gene family, locat ed 10 kilobases downstream from the AFP locus. The new gene, named alp ha-albumin (alpha ALB), is selectively expressed in the liver at late stages of development. The alpha ALB mRNA sequence encodes a predicted secreted protein with the typical triple domain disulfide cross-linke d structure. Comparisons of coding and promoter sequences suggest that alpha ALB could be a phylogenetic intermediate between the ALB and AF P genes. The developmental switch between alpha ALB gene activation an d AFP gene repression suggests new regulatory interplays at the albumi n locus and adult stage-specific ligand binding functions carried out by the alpha ALB gene product.