We describe post-transcriptional regulation of the chromosomal gene, gef, from Escherichia coli. The gef gene is a member of a gene family consisting of the chromosomal gef and relF genes from Escherichia coli and the hok, flmA, smB, and pndA genes, which are situated on conjugative plasmids. All the genes encode small, toxic proteins of approximately 50 amino acids which are functionally and structurally homologous. Furthermore, the gene family shares post-transcriptional regulation of expression, albeit by different mechanisms. We demonstrate here that translation of gef is coupled to an upstream open reading frame which, in turn, is regulated by a transacting factor, probably an antisense RNA.