The hammerhead ribozyme is an RNA motif that catalyzes reversible cleavage and ligation reactions at a specific site within an RNA molecule. It is one of several catalytic RNAs (ribozymes) known to occur in nature. It serves as a model system for research on the structure and properties of RNA, and is used for targeted RNA cleavage experiments, some with proposed therapeutic applications. Named for the resemblance of early secondary structure diagrams to a hammerhead shark,[1] hammerhead ribozymes were originally discovered in two classes of plant virus-like RNAs: satellite RNAs and viroids. They are also known in some classes of retrotransposons, including the retrozymes.[2] The hammerhead ribozyme motif has been ubiquitously reported in lineages across the tree of life.[3][4]
The self-cleavage reactions, first reported in 1986,[5][6] are part of a rolling circle replication mechanism. The hammerhead sequence is sufficient for self-cleavage[7] and acts by forming a conserved three-dimensional tertiary structure.