The cells of higher organisms store their genetic material, the genome, in the so-called nucleus where they organize transcription of DNA into messenger-RNA, the blueprint for proteins. The messenger-RNA leaves the cell to be decoded by ribosomes that synthesize the respective proteins. Transcription factors, also proteins, control in the nucleus which parts of the cells' genomes are transcribed. Naturally, the access to the nucleus as well as exit from it must be restricted to transcription factors and related biomolecules. This is achieved by the nuclear pores, wide channels lined with brushes of polymers. The polymers are disordered proteins and prevent passage for most cellular proteins, except for so-called transport factors which bus transcription factors, messenger RNA, and certain larger biomolecule into and out of the nucleus. How transport factors are permitted to pass the nuclear pores, despite many studies, has been largely unknown. Molecular dynamics simulations, based on relevant crystallographic structures, using NAMD provided a comprehensive picture on the passage mechanism as reported recently. The simulations, analyzed with VMD, revealed that transport factors are dotted rather regularly on their surface with spots that bind to the brushes of nuclear pore proteins. While any protein may accidentally exhibit such a binding spot or two, only transport factors offer a regular pattern of such spots on their surface that apparently is their passport permitting them movement into and out of the nucleus, i.e., helping them to glide through the pores' protein brushes. More on simulations of transport factors can be found here.

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