Actinomycins are well-known inhibitors of transcription in both prokaryotes and eukaryotes, due to their planar structure, which allow them to intercalate into GC-rich DNA. As such, they have strong anti-neoplastic activities, although their high toxicity has restricted therapeutic use to only a few tumor types. Structural redesign of this compound class to minimize toxicity is a main goal of research. Ullrich Keller of the Technical University of Berlin, Germany, and colleagues show- contrary to their expectation of a more humdrum assembly of genes encoding biosynthetic steps, self-resistance, and regulation-that these genes actually form in duplicate blocks, "oriented to each other in inverted symmetry, and constituting the arms of a huge palindrome with the single copy of the assembly molecule nonribosomal peptide synthase in their middle," says Keller. "Insertion elements and integrase gene fragments flanking the palindrome at both ends point to integration of the gene cluster into the host's genome via transposition of a mobile genetic element." Nothing like it has ever been found before, he says. The paper is valuable both in cancer research and as a foundation for examining evolution of actinomycin biosynthesis genes among the soil-dwelling actinomycetes.