Fig. 1From: Hammerhead ribozymes going viralA model for the propagation of retrozymes in plants (modified from Cervera et al. [3]). Upon transcription, ligation-competent linear retrozymes are generated by hammerhead ribozyme (HHRz) self-cleavage. The covalent closure of the cleavage product yields circular RNA (circRNA) retrozymes of plus polarity (+). These serve as templates for reverse transcriptase, yielding cDNA that can be integrated into the genome by means of proteins encoded by autonomous retroelements. The observation of multimeric retrozyme RNA of minus polarity (–) suggests an additional RNA replication mechanism, involving a plant RNA-dependent RNA polymerase activityBack to article page