AbstractEukaryotic cells are defined by the compartmentalization of the cytoplasm into organelles, the largest of which is the nucleus, which contains the cellular DNA. Transport into and out of the nucleus is highly regulated and is traditionally thought to occur solely through nuclear pores. However, a small number of papers has repeatedly shown vesicular budding from the nuclear envelopes in different organisms. We used electron microscopy to identify such nuclear envelope budding events in a human cell line,Caenorhabditis elegansworms, the two yeastsSaccharomyces cerevisiaeandSchizosaccharomyces pombeand the parasitic protistTrypanosoma brucei. Progressing to electron tomography, the finer details of the 3D architecture of such budding events was revealed. We summarize all the organisms in which this mode of translocation over the nuclear envelope has been observed and conclude that this may be a fundamental, evolutionary conserved mechanism of transport inside eukaryotic cells.
Characterization of DNA transport in the thermophilic bacterium Thermus thermophilus HB27
