Actinomycin D (ActD)

Actinomycin D, is the most significant member of actinomycines, which are a class of polypeptide antibiotics isolated from soil bacteria of the genus Streptomyces.Actinomycin D is shown to have the ability to inhibit transcription. It does this by binding DNA at the transcription initiation complex and preventing elongation of RNA chain by RNA polymerase. Because Actinomycin can bind DNA duplexes, it can also interfere with DNA replication, although other chemicals such as hydroxyurea are better suited for use in the laboratory as inhibitors of DNA synthesis. Actinomycin D and its fluorescent derivative, 7-aminoactinomycin D, are used as stains in microscopy and flow cytometry applications. The affinity of these stains/compounds for GC-rich regions of DNA strands makes them excellent markers for DNA. 7-AAD binds to single stranded DNA; therefore it is a useful tool in determining apoptosis and distinguishing between dead cells and live ones.