Cellular dynamics of tRNAs and their genes.

This discussion focuses on the cellular dynamics of tRNA transcription, processing, and turnover. Early tRNA biosynthesis steps are shared among most tRNAs, while later ones are often individualized for specific tRNAs. In yeast, tRNA transcription and early processing occur coordinately in the nucleolus, requiring topological arrangement of approximately 300 tRNA genes and early processing enzymes to this site; later processing events occur in the nucleoplasm or cytoplasm. tRNA nuclear export requires multiple exporters which function in parallel and the export process is coupled with other cellular events. Nuclear-cytoplasmic tRNA subcellular movement is not unidirectional as a retrograde pathway delivers mature cytoplasmic tRNAs to the nucleus. Despite the long half-lives, there are multiple pathways to turnover damaged tRNAs or normal tRNAs upon cellular stress.