By exploiting the DNA of a thermophilic fungus that grows optimally between 50 and 60 degrees Celsius Heidelberg scientists have reconstructed a central piece of the cell's nuclear envelope in the test-tube.
This structure is part of the nuclear pore complex, which mediates the exchange of material between the cell nucleus and its surrounding compartment, the cytoplasm. To achieve their goals, researchers from Heidelberg University and the European Molecular Biology Laboratory (EMBL) sequenced the genome of the thermophilic eukaryote Chaetomium thermophilum and identified all the proteins of the nuclear pore transport channel. This breakthrough enabled them to assemble a long sought-after central pillar of the nuclear pore. The findings reported by Prof. Dr. Ed Hurt and Dr. Peer Bork have been published in „Cell“ (22 July 2011).
A very prominent development in the evolution of a eukaryotic cell was the formation of a nuclear envelope around the genetic information, the chromosomes, which formed a barrier and hindered exchange of material between the nucleus and the cytoplasm. However, nuclear pore complexes have co-evolved as transport channels in the nuclear envelope to allow traffic between these two cellular compartments. Each nuclear pore complex is composed of about 30 different components called nucleoporins or Nups, which exist in many copies so that ca. 500 subunits build up this complex nano-machine.
Previously, the core structure of the nuclear pore complex was unknown, since it was difficult to reconstruct this assembly outside of the cell, due to the instability of isolated nuclear pore components. Thus, Prof. Hurt and his team sought to utilize thermostable nuclear pore building blocks from a thermophilic eukaryote to foster biochemical reconstitution. It is well known that proteins derived from heat-loving bacteria, which can still grow at temperatures above 100 degrees Celsius, are extremely robust. Notably, such exotic organisms also exist in the kingdom of eukaryote life. One example is Chaetomium thermophilum, a filamentous fungus, involved in the decomposition of plant material, a biological process generating heat as high as 70 degrees Celsius.
At Heidelberg University Biochemistry Center, Prof. Hurt and his team have deciphered the entire DNA sequence of the thermophilic fungus consisting of approximately 28 million DNA bases. Dr. Bork and his research group at the European Molecular Biology Laboratory have annotated the genome sequence and identified all the proteins in this organism, more than 7,000. Among them were the 30 Nups of the nuclear pore complex. By using these thermophilic Nups, Ed Hurt's team finally succeeded in reconstituting a central structure of the nuclear pore complex in the test-tube. Prof. Hurt and Dr. Bork are confident that their findings will foster the development of this eukaryotic thermophile as a model organism to study complicated eukaryotic molecular machines.
For more information, go to http://www.uni-heidelberg.de/zentral/bzh/hurt.
Marietta Fuhrmann-Koch | idw
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