Actinomycin D is an antibiotic that inhibits nucleic acid synthesis, particularly RNA synthesis.MECHANISM1.Intercalation into DNA:Actinomycin D is a flat, planar molecule that can insert itself between the base pairs of DNA.• It has a preference for GC-rich regions of DNA due to the structure of its binding site.2.Binding to DNA:Actinomycin D binds tightly to the double helix of DNA, specifically at GC base pairs.•This binding distorts the structure of the DNA helix and prevents proper separation of the DNA strands.3.Inhibition of RNA Polymerase:DNA-dependent RNA polymerase is the enzyme responsible for transcribing DNA into RNA.•Actinomycin D's binding to DNA near the transcription start site interferes with the movement of RNA polymerase along the DNA template.4.RNA Synthesis Inhibition:The interference with RNA polymerase activity prevents the synthesis of messenger RNA (mRNA) and other types of RNA.• As a result, protein synthesis is inhibited because the cell cannot produce the necessary mRNA templates.•Actinomycin D's mechanism of action makes it a potent inhibitor of transcription in both bacterial and eukaryotic cells.• It is particularly used in cancer chemotherapy to prevent cancer cells from replicating and producing necessary proteins for growth