Electron Microscopy: Transport

Electron micrographs showing mRNP (messenger RNA associated with protein) during transport through the nuclear pore complex (NPC).

A - The spherical mRNP particle associates with the NPC.

B - The mRNP particle becomes pear-shaped in the beginning of the transport. The mRNP is transported with the 5' end in the lead.

C - The mRNP particle later becomes elongated and rod-shaped as it accomodates to the maximal opening of the NPC during the transport.

D - At the cytoplasmic side, the mRNP particle unfolds into a zig-zag pattern and ribosomes may attach as protein synthesis starts.

The nucleus is at the top and the cytoplasm at the bottom. Bar 100nm.

E - Tangential section showing the NPCs in a "face on" view. The arrows denote some mRNP during transport.
Bar 100nm.

(see also another micrograph of the same view, using another preparation technique)

Images kindly provided by Hans Mehlin, Bertil Daneholt, Ulf Skoglund. Previosly published in Cell 69: 605-613 1992, "Translocation of a Specific Premessenger Ribonucleoprotein Particle through the Nuclear Pore Studied with Electron Microscope Tomography".