Transcriptional Complexity from Dynamic Interaction Networks In Vivo

The last decades have lead to the identification and characterization of most key steps in gene expression including chromatin remodeling, transcription, RNA processing, export and translation. Extensive biochemical, genetic and molecular approaches have not only revealed the key players involved in these processes, but have yielded detailed insights into the molecular behavior of many. Despite the wealth of molecular and structural information of distinct processes of gene expression and of single molecular components, fundamental aspects of the system behavior of the gene expression machinery have remained elusive. It is just now becoming clear that the single steps in the gene expression process are tightly interlinked and virtually nothing is known about how the various components of genome regulation and expression machineries are integrated into presumably complex networks of interactions and pathways. Even more elusive has been the elucidation of how gene expression processes occur in their natural setting of the cell nucleus in intact living cells. Recent advances in qualitative and quantitative imaging methods are beginning to provide tools to study the complexity of the gene expression process in living cells. We briefly review here some emerging in vivo imaging technologies and summarize the recent results and the conceptual impact these methods are making on understanding transcriptional complexity in vivo.