Current Biology
Volume 9, Issue 6, 25 March 1999, Pages 285-291
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Research paper
Movement of nuclear poly(A) RNA throughout the interchromatin space in living cells

https://doi.org/10.1016/S0960-9822(99)80136-5Get rights and content
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Abstract

Background: Messenger RNA (mRNA) is transcribed and processed in the nucleus of eucaryotic cells and then exported to the cytoplasm through nuclear pores. It is not known whether the movement of mRNA from its site of synthesis to the nuclear pore is directed or random. Directed movement would suggest that there is an energy-requiring step in addition to the step required for active transport through the pore, whereas random movement would indicate that mRNAs can make their way to the nuclear envelope by diffusion.

Results: We devised a method to visualize movement of endogenous polymerase II transcripts in the nuclei of living cells. Oligo(dT) labeled with chemically masked (caged) fluorescein was allowed to penetrate cells and hybridize to nuclear poly(A) RNA. Laser spot photolysis then uncaged the oligo(dT) at a given intranuclear site and the resultant fluorescent, hybridized oligo(dT) was tracked using high-speed imaging microscopy. Poly(A) RNA moved away from the uncaging spot in all directions with a mean square displacement that varied linearly with time, and the same apparent diffusion coefficient was measured for the movement at both 37°C and 23°C. These properties are characteristic of a random diffusive process. High resolution three-dimensional imaging of live cells containing both Hoechst-labeled chromosomes and uncaged oligo(dT) showed that, excluding nucleoli, the poly(A) RNA could access most, if not all, of the non-chromosomal space in the nucleus.

Conclusions: Poly(A) RNA can move freely throughout the interchromatin space of the nucleus with properties characteristic of diffusion.

Cited by (0)

JC Politz and T Pederson, Department of Biochemistry and Molecular Biology, Biomedical Imaging Center, University of Massachusetts Medical School, Worcester, Massachusetts 01605, USA.

E-mail address for JC Politz (corresponding author): [email protected].

RA Tuft, Department of Physiology, Biomedical Imaging Center, University of Massachusetts Medical School, Worcester, Massachusetts 01605, USA.

RH Singer, Department of Anatomy and Structural Biology and Cell Biology, Albert Einstein College of Medicine, Bronx, New York 10461, USA.