title: Mechanism of mRNA transport in the nucleus.
abstract: The mechanism of transport of mRNA-protein (mRNP) complexes from transcription sites to nuclear pores has been the subject of many studies. Using molecular beacons to track single mRNA molecules in living cells, we have characterized the diffusion of mRNP complexes in the nucleus. The mRNP complexes move freely by Brownian diffusion at a rate that assures their dispersion throughout the nucleus before they exit into the cytoplasm, even when the transcription site is located near the nuclear periphery. The diffusion of mRNP complexes is restricted to the extranucleolar, interchromatin spaces. When mRNP complexes wander into dense chromatin, they tend to become stalled. Although the movement of mRNP complexes occurs without the expenditure of metabolic energy, ATP is required for the complexes to resume their motion after they become stalled. This finding provides an explanation for a number of observations in which mRNA transport appeared to be an enzymatically facilitated process.
authors.affiliation: Department of Molecular Genetics, Public Health Research Institute, 225 Warren Street, Newark, NJ 07103, USA.
authors.forename: Diana Y
authors.initials: DY
authors.lastname: Vargas
authors.forename: Arjun
authors.initials: A
authors.lastname: Raj
authors.forename: Salvatore A E
authors.initials: SA
authors.lastname: Marras
authors.forename: Fred Russell
authors.initials: FR
authors.lastname: Kramer
authors.forename: Sanjay
authors.initials: S
authors.lastname: Tyagi
mesh_terms: D021581:Active Transport, Cell Nucleus; D000255:Adenosine Triphosphate / Q000378:metabolism; D000818:Animals; D016466:CHO Cells; D002467:Cell Nucleus / Q000378:metabolism*; D003080:Cold Temperature; D006224:Cricetinae; D003412:Cricetulus; D004058:Diffusion; D017930:Genes, Reporter; D012333:RNA, Messenger / Q000378:metabolism*; D012261:Ribonucleoproteins / Q000378:metabolism
chemical_list: D012333:RNA, Messenger; D012261:Ribonucleoproteins; C026452:messenger ribonucleoprotein; D000255:Adenosine Triphosphate