Overlapping genes in bacterial and phage genomes

Overlapping of genes was first reported for small viruses and was initially considered a phenomenon related to the natural selection favoring the tren d of genome size reduction. Later, overlapping genes were found in the geno mes of bacteria, mitochondria, and chloroplasts; numerous evidence of their transcriptional and posttranscriptional interaction was provided. We sugge st that overlapping of the genes is important for complex regulation of gen e expression and/or for better interaction at the transcriptional or transl ational level. This review describes various types of overlapping genes and operons and the molecular mechanisms of overlapping gene interaction.