Amplification and characterization of a beta-globin gene synthesized in vitro

Abstract

Full-length, double-stranded globin DNA was synthesized in vitro starting from rabbit globin mRNA. Several restriction endonuclease cleavage sites with known recognition sequences were mapped on this DNA as a means of assessing the accuracy of in vitro synthesis. By comparing this map with the nucleotide sequences known or predicted from the amino acid sequences of alpha-and beta-chain rabbit hemoglobin, it was possible to show that the synthetic globin DNA is a faithful copy of beta-globin mRNA. Amplification of the synthetic globin DNA was achieved by inserting the molecule into the plasmid PMB9 using the poly(dA)-(dT) joining procedure, and transforming E. coli with the hybrid DNA. Transformants carrying beta-globin DNA were identified by colony hybridization using purified 125I-beta-mRNA probe. Comparison of the restriction maps of the synthetic and inserted globin DNAs showed that the entire synthetic globin DNA molecule was amplified without sequence rearrangements. Both the synthetic and the cloned DNA include the entire coding sequence of the beta-globin gene plus a substantial portion of the untranslated regions flanking the structural gene.