Cell Biology

Blocked Pores

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Science  03 Nov 2000:
Vol. 290, Issue 5493, pp. 901
DOI: 10.1126/science.290.5493.901d

During nuclear import proteins are transported from the cytosol across the double membrane of the nuclear envelope through nuclear pores. Nuclear import substrates possess short peptide motifs, known as nuclear localization signals (NLSs), that are specifically recognized by the nuclear import apparatus. One component of the nuclear import machinery is the protein p10, which directly binds to the small GTPase RanGDP and helps mediate import of proteins bearing classical NLSs.

In studying how p10 itself is transported across the nuclear envelope, Lane et al. discovered a single amino acid mutation that generates a dominant negative form of the protein. Mutated p10 imports RanGDP into the nucleus faster than wild-type p10, but in so doing appears to block access to components of the nuclear pore used by the karyopherins. The karyopherins are distinct components of the nuclear import machinery that bind to NLS motifs and are transported along with their cargoes across the nuclear pore. Therefore, relatively modest alterations to the interactions of nuclear import facilitators with the nuclear pore may result in profound changes to the throughput of nuclear entry pathways. — SMH

J. Cell Biol.151, 321 (2000).

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