Circadian regulation of gene expression: at the crossroads of transcriptional and post-transcriptional regulatory networks.

Gene expression programs activated in response to, or in anticipation of, environmental changes involve sequential steps, from transcription and RNA processing to nuclear export and translation. Here we review recent advances in our understanding of the multiple regulatory layers that control the oscillations in gene expression associated with daily rhythms in metabolism and physiology across eukaryotic organisms. Whereas many genes show coordinated oscillations in transcription, RNA processing and translation, others show significant temporal disconnections between these processes. Thus, circadian oscillations constitute an ideal system for examining how multiple transcriptional and post-transcriptional regulatory steps are integrated to maximize organismal adjustments to environmental conditions.