Isolation of active messenger RNA for αS casein from bound polyribosomes of mammary gland

Abstract RNAs have been extracted from mammary bound polyribosomes and purified by sucrose gradient centrifugation. A cell free mammary system (homologous, except for the addition of initiation factors of reticulocyte origin) and a lysate of reticulocytes, have been used to assay biologically active messenger RNA. One of these messenger RNAs directs the synthesis of a product with electrophoretic and immunological properties analogous to α S casein.