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Regulation of gene expression is key determinant to cell structure and function. RNA localization, where specific mRNAs are transported to subcellular regions and then translated, is highly conserved in eukaryotes ranging from yeast to extremely specialized and polarized cells such as neurons. Messenger RNA and associated proteins (mRNP) move from the site of transcription in the nucleus to their final destination in the cytoplasm both passively through diffusion and actively via directed transport. Dysfunction of RNA localization, transport and translation machinery can lead to pathology. Single-molecule live-cell imaging techniques have revealed unique features of this journey with unprecedented resolution. In this review, we highlight key recent findings that have been made using these approaches and possible implications for spatial control of gene function. [ABSTRACT FROM AUTHOR]

The nuclear pore complex (NPC) has long been viewed as a point-like entry and exit channel between the nucleus and the cytoplasm. New data support a different view whereby the complex displays distinct spatial dynamics of variable duration ranging from milliseconds to events spanning the entire cell cycle. Discrete interaction sites outside the central channel become apparent, and transport regulation at these sites seems to be of greater importance than currently thought. Nuclear pore components are highly active outside the NPC or impact the fate of cargo transport away from the nuclear pore. The NPC is a highly dynamic, crowded environment—constantly loaded with cargo while providing selectivity based on unfolded proteins. Taken together, this comprises a new paradigm in how we view import/export dynamics and emphasizes the multiscale nature of NPC-mediated cellular transport. [ABSTRACT FROM AUTHOR]

Understanding the different molecular mechanisms responsible for gene expression has been a central interest of molecular biologists for several decades. Transcription, the initial step of gene expression, consists of converting the genetic code into a dynamic messenger RNA that will specify a required cellular function following translocation to the cytoplasm and translation. We now possess an in-depth understanding of the mechanism and regulations of transcription. By contrast, an understanding of the dynamics of an individual gene''s expression in real time is just beginning to emerge following recent technological developments. [Copyright &y& Elsevier]

Recent developments in reagent design can address problems in single cells that were not previously approachable. We have attempted to foresee what will become possible, and the sorts of biological problems that become tractable with these novel reagents. We have focused on the novel fluorescent proteins that allow convenient multiplexing, and provide for a time-dependent analysis of events in single cells. Methods for fluorescently labeling specific molecules, including endogenously expressed proteins and mRNA have progressed and are now commonly used in a variety of organisms. Finally, sensitive microscopic methods have become more routine practice. This article emphasizes that the time is right to coordinate these approaches for a new initiative on single cell imaging of biological molecules. [Copyright &y& Elsevier]

After the export from the nucleus it turns out that all mRNAs are not treated equally. Not only is mRNA subject to translation, but also through RNA-binding proteins and other trans-acting factors, eukaryotic cells interpret codes for spatial sorting within the mRNA sequence. These codes instruct the cytoskeleton and translation apparatus to make decisions about where to transport and when to translate the intended protein product. Signaling pathways decode extra-cellular cues and can modify transport and translation factors in the appropriate cytoplasmic space to achieve translation locally. Identifying regulatory sites on transport factors as well as novel physiological functions for well-known translation factors has provided significant advances in how spatially controlled translation impacts cell function. [Copyright &y& Elsevier]