Chemical synthesis and cloning of secretin gene.

A DNA duplex coding for the 27 amino acids of secretin has been synthesized and cloned. In designing the sequence of the gene, computer analysis has been applied. The following factors have been considered: selection of codon usage in favour of expression in yeast; design of various sites useful in gene cloning, gene modification and expressed product purification; avoiding the repeat sequences which may interfere in the ligation of the synthetic fragments. The synthesis involved preparation of 12 oligodeoxyribonucleotides (12-mer to 24-mer in length) by phosphate triester and phosphite triester method, purification by polyacrylamide gel electrophoresis (PAGE). A new plasmid pWS1 was constructed by insertion of the enzymatic ligated gene fragment into plasmid pWR13.