Dynamic Encounters of Genes and Transcripts with the Nuclear Pore

Transcribed mRNA molecules must reach the cytoplasm to undergo translation. Technological developments in imaging have placed mRNAs under the spotlight, allowing the quantitative study of the spatial and temporal dynamics of the nucleocytoplasmic mRNA export process. Here, we discuss studies that have used such experimental approaches to demonstrate that gene tethering at the nuclear pore complex (NPC) regulates mRNA expression, and to characterize mRNA dynamics during transport in real time. The paths taken by mRNAs as they move from their sites of transcription and travel through the nucleoplasm, in between chromatin domains, and finally through the NPC, can now be observed in detail.

TrendsHigh-resolution microscopy enables real-time measurements of nuclear mRNA transport in different cell types, including the timing of mRNA transport to the pore and the differences in nuclear dwell times between transcripts, some of which may remain in the nucleus for many hours.Using imaging techniques, it is possible to detect separate scanning and docking events of mRNAs at the NPC, and to measure the rapid steps of export per se at the nuclear basket, in the channel, and before release on the cytoplasmic side. Even rare bidirectional transport events of mRNA can be observed.Regulation of gene expression at the pore can be governed through tethering of genomic regions to the pore via interactions with nucleoporins and transcription factors. This can lead to either induction or repression of transcriptional activity of genes repositioned at the nuclear periphery.