RNA: Versatility in form and function

RNA performs a remarkable range of functions in all cells. In addition to i ts central role in information transfer from DNA to protein, it is essentia l for functions as diverse as RNA processing, chromosome end-maintenance an d dosage compensation. The versatility of RNA derives from its unique abili ty to use direct readout via base-pairing for sequence specific targeting ( or templating) in combination with its capacity to form elaborate three dim ensional structures. Such structures can perform catalysis or serve as prot ein recognition surfaces. In this short review, we attempt to give a flavor for the diversity of functional RNAs in the cell and highlight, using sele cted examples, two quite distinct activities, catalysis and sequence specif ic targeting. Within each section. we discuss how the lessons we have learn ed from these systems may apply to other, less well understood, RNAs.