Gene Regulation by Antisense DNA Produced in Vivo(∗)

Antisense technology has been widely used for regulating gene expression. Single-stranded RNA or DNA complementary to a target mRNA can inhibit the translation of the mRNA. Antisense RNA is produced in vivo, while antisense DNA is chemically synthesized as an oligonucleotide, which is extracellularly added to the cells. To maintain the effect of antisense DNA, a synthetic oligonucleotide has to be constantly added to the system. An advantage of antisense DNA over antisense RNA is that the target mRNA hybridized with the antisense DNA can be specifically digested by ribonuclease H. Here, we attempted to produce in vivo short single-stranded DNAs complementary to a specific mRNA. We demonstrate that such antisense oligodeoxyribonucleotide of a desired sequence can be produced in Escherichia coli using a retron, a bacterial retroelement, as a vector and that the antisense DNA thus produced in vivo can effectively inhibit the expression of a specific E. coli gene, such as the gene for the major outer membrane lipoprotein.