Karyopherin α7 (KPNA7), a divergent member of the importin α family of nuclear import receptors

• Main Authors: Kelley Joshua B, Talley Ashley M, Spencer Adam, Gioeli Daniel, Paschal Bryce M
• Format: Article
• Language: English
• Published: BMC 2010-08-01
• Series: BMC Cell Biology
• Online Access: http://www.biomedcentral.com/1471-2121/11/63

<p>Abstract</p> <p>Background</p> <p>Classical nuclear localization signal (NLS) dependent nuclear import is carried out by a heterodimer of importin α and importin β. NLS cargo is recognized by importin α, which is bound by importin β. Importin β mediates translocation of the complex through the central channel of the nuclear pore, and upon reaching the nucleus, RanGTP binding to importin β triggers disassembly of the complex. To date, six importin α family members, encoded by separate genes, have been described in humans.</p> <p>Results</p> <p>We sequenced and characterized a seventh member of the importin α family of transport factors, karyopherin α 7 (KPNA7), which is most closely related to KPNA2. The domain of KPNA7 that binds Importin β (IBB) is divergent, and shows stronger binding to importin β than the IBB domains from of other importin α family members. With regard to NLS recognition, KPNA7 binds to the retinoblastoma (RB) NLS to a similar degree as KPNA2, but it fails to bind the SV40-NLS and the human nucleoplasmin (NPM) NLS. KPNA7 shows a predominantly nuclear distribution under steady state conditions, which contrasts with KPNA2 which is primarily cytoplasmic.</p> <p>Conclusion</p> <p>KPNA7 is a novel importin α family member in humans that belongs to the importin α2 subfamily. KPNA7 shows different subcellular localization and NLS binding characteristics compared to other members of the importin α family. These properties suggest that KPNA7 could be specialized for interactions with select NLS-containing proteins, potentially impacting developmental regulation.</p>