Cellular organization of the transfer of genetic information

Abstract

Each step involved in the transfer of genetic information is spatially regulated in eukaryotic cells, as transcription, translation and mRNA degradation mostly occur in distinct functional compartments (e.g., nucleus, cytoplasm and P-bodies). At first glance in bacteria, these processes seem to take place in the same compartment - the cytoplasm - because of the conspicuous absence of membrane-enclosed organelles. However, it is becoming increasingly evident that mRNA-related processes are also spatially organized inside bacterial cells, and that this organization affects cellular function. The aims of this review are to summarize the current knowledge about this organization and to consider the mechanisms and forces shaping the cell interior. The field stands at an exciting point where new technologies are making long-standing questions amenable to experimentation.

Figure 1

Two distinct patterns of spatial organization of chromosomes and ribosomes in bacteria.

Figure 2

Models to reconcile the transcription-translation coupling with the spatial separation of DNA and ribosomes in bacteria that have the cellular organization illustrated in Figure 1A. See text for details about these three non-exclusive models.

Figure 3

FRAP and super-resolution single-molecule microscopy probe ribosome dynamics at different spatial and temporal scales. FRAP-based experiments examine the mobility of the ribosome ensemble (shown in yellowgreen) whereas super-resolution single-molecule experiments track individual ribosomes (depicted as red spheres). The green line shows the trajectory and rapid escape of a free ribosome whereas the blue line represents the trajectory of a ribosome bound to an mRNA, displaying motion in a spatially confined microdomain.