Importin subunit alpha-4 explained

Importin subunit alpha-4 also known as karyopherin subunit alpha-3 is a protein that in humans is encoded by the KPNA3 gene.^{[1] [2]}

The transport of molecules between the nucleus and the cytoplasm in eukaryotic cells is mediated by the nuclear pore complex (NPC) which consists of 60–100 proteins and is probably 120 million daltons in molecular size. Small molecules (up to 70 kD) can pass through the nuclear pore by nonselective diffusion; larger molecules are transported by an active process. Most nuclear proteins contain short basic amino acid sequences known as nuclear localization signals (NLSs). KPNA3, encodes a protein similar to certain nuclear transport proteins of Xenopus and human. The predicted amino acid sequence shows similarity to Xenopus importin, yeast SRP1, and human RCH1 (KPNA2), respectively. The similarities among these proteins suggests that karyopherin alpha-3 may be involved in the nuclear transport system.^[3]

Interactions

KPNA3 has been shown to interact with KPNB1.^[4]

Further reading

• Bukrinsky MI, Haffar OK . HIV-1 nuclear import: in search of a leader . Front. Biosci. . 2 . d578–87 . 2004 . 4 . 9366553 . 10.2741/A213 . free .
• Bukrinsky MI, Haffar OK . HIV-1 nuclear import: matrix protein is back on center stage, this time together with Vpr . Mol. Med. . 4 . 3 . 138–43 . 1998 . 9562972 . 10.1007/BF03401911. 2230352 .
• Bukrinsky MI, Sharova N, Dempsey MP, etal . Active nuclear import of human immunodeficiency virus type 1 preintegration complexes . Proc. Natl. Acad. Sci. U.S.A. . 89 . 14 . 6580–4 . 1992 . 1631159 . 10.1073/pnas.89.14.6580 . 49545 . 1992PNAS...89.6580B . free .
• Sharova N, Bukrinskaya A . p17 and p17-containing gag precursors of input human immunodeficiency virus are transported into the nuclei of infected cells . AIDS Res. Hum. Retroviruses . 7 . 3 . 303–6 . 1991 . 2064827 . 10.1089/aid.1991.7.303 .
• Di Marzio P, Choe S, Ebright M, etal . Mutational analysis of cell cycle arrest, nuclear localization and virion packaging of human immunodeficiency virus type 1 Vpr . J. Virol. . 69 . 12 . 7909–16 . 1996 . 10.1128/JVI.69.12.7909-7916.1995 . 7494303 . 189735 .
• Gallay P, Swingler S, Song J, etal . HIV nuclear import is governed by the phosphotyrosine-mediated binding of matrix to the core domain of integrase . Cell . 83 . 4 . 569–76 . 1995 . 7585960 . 10.1016/0092-8674(95)90097-7 . free .
• Freed EO, Englund G, Martin MA . Role of the basic domain of human immunodeficiency virus type 1 matrix in macrophage infection . J. Virol. . 69 . 6 . 3949–54 . 1995 . 7745752 . 10.1128/JVI.69.6.3949-3954.1995. 189124 .
• Gallay P, Swingler S, Aiken C, Trono D . HIV-1 infection of nondividing cells: C-terminal tyrosine phosphorylation of the viral matrix protein is a key regulator . Cell . 80 . 3 . 379–88 . 1995 . 7859280 . 10.1016/0092-8674(95)90488-3 . free .
• von Schwedler U, Kornbluth RS, Trono D . The nuclear localization signal of the matrix protein of human immunodeficiency virus type 1 allows the establishment of infection in macrophages and quiescent T lymphocytes . Proc. Natl. Acad. Sci. U.S.A. . 91 . 15 . 6992–6 . 1994 . 8041734 . 10.1073/pnas.91.15.6992 . 44324 . 1994PNAS...91.6992V . free .
• Heinzinger NK, Bukinsky MI, Haggerty SA, etal . The Vpr protein of human immunodeficiency virus type 1 influences nuclear localization of viral nucleic acids in nondividing host cells . Proc. Natl. Acad. Sci. U.S.A. . 91 . 15 . 7311–5 . 1994 . 8041786 . 10.1073/pnas.91.15.7311 . 44389 . 1994PNAS...91.7311H . free .
• Bukrinsky MI, Haggerty S, Dempsey MP, etal . A nuclear localization signal within HIV-1 matrix protein that governs infection of non-dividing cells . Nature . 365 . 6447 . 666–9 . 1993 . 8105392 . 10.1038/365666a0 . 9524217 . 1993Natur.365..666B . 25678 .
• Maruyama K, Sugano S . Oligo-capping: a simple method to replace the cap structure of eukaryotic mRNAs with oligoribonucleotides . Gene . 138 . 1–2 . 171–4 . 1994 . 8125298 . 10.1016/0378-1119(94)90802-8 .
• Dubrovsky L, Ulrich P, Nuovo GJ, etal . Nuclear localization signal of HIV-1 as a novel target for therapeutic intervention . Mol. Med. . 1 . 2 . 217–30 . 1996 . 8529100 . 10.1007/BF03401569. 2229944 .
• Gallay P, Stitt V, Mundy C, etal . Role of the karyopherin pathway in human immunodeficiency virus type 1 nuclear import . J. Virol. . 70 . 2 . 1027–32 . 1996 . 8551560 . 10.1128/JVI.70.2.1027-1032.1996. 189908 .
• Bukrinskaya AG, Ghorpade A, Heinzinger NK, etal . Phosphorylation-dependent human immunodeficiency virus type 1 infection and nuclear targeting of viral DNA . Proc. Natl. Acad. Sci. U.S.A. . 93 . 1 . 367–71 . 1996 . 8552640 . 10.1073/pnas.93.1.367 . 40239 . 1996PNAS...93..367B . free .
• Sato A, Yoshimoto J, Isaka Y, etal . Evidence for direct association of Vpr and matrix protein p17 within the HIV-1 virion . Virology . 220 . 1 . 208–12 . 1996 . 8659115 . 10.1006/viro.1996.0302 . free .
• Popov S, Dubrovsky L, Lee MA, etal . Critical role of reverse transcriptase in the inhibitory mechanism of CNI-H0294 on HIV-1 nuclear translocation . Proc. Natl. Acad. Sci. U.S.A. . 93 . 21 . 11859–64 . 1996 . 8876228 . 10.1073/pnas.93.21.11859 . 38149 . 1996PNAS...9311859P . free .
• Freed EO, Englund G, Maldarelli F, Martin MA . Phosphorylation of residue 131 of HIV-1 matrix is not required for macrophage infection . Cell . 88 . 2 . 171–3; discussion 173–4 . 1997 . 9008157 . 10.1016/S0092-8674(00)81836-X . free .
• Gallay P, Hope T, Chin D, Trono D . HIV-1 infection of nondividing cells through the recognition of integrase by the importin/karyopherin pathway . Proc. Natl. Acad. Sci. U.S.A. . 94 . 18 . 9825–30 . 1997 . 9275210 . 10.1073/pnas.94.18.9825 . 23276 . 1997PNAS...94.9825G . free .

Notes and References

1. Takeda S, Fujiwara T, Shimizu F, Kawai A, Shinomiya K, Okuno S, Ozaki K, Katagiri T, Shimada Y, Nagata M, Watanabe T, Takaichi A, Kuga Y, Suzuki M, Hishigaki H, Takahashi E, Shin S, Nakamura Y, Hirai Y . Isolation and mapping of karyopherin alpha 3 (KPNA3), a human gene that is highly homologous to genes encoding Xenopus importin, yeast SRP1 and human RCH1 . Cytogenet Cell Genet . 76 . 1–2 . 87–93 . Jun 1997 . 9154134 . 10.1159/000134521 .
2. Nachury MV, Ryder UW, Lamond AI, Weis K . Cloning and characterization of hSRP1 gamma, a tissue-specific nuclear transport factor . Proc Natl Acad Sci U S A . 95 . 2 . 582–7 . Feb 1998 . 9435235 . 18463 . 10.1073/pnas.95.2.582 . 1998PNAS...95..582N . free .
3. Web site: Entrez Gene: KPNA3 karyopherin alpha 3 (importin alpha 4).
4. Köhler . M . Speck C . Christiansen M . Bischoff F R . Prehn S . Haller H . Görlich D . Hartmann E . Nov 1999 . Evidence for distinct substrate specificities of importin alpha family members in nuclear protein import . Mol. Cell. Biol. . 19 . 11 . 7782–91 . UNITED STATES. 0270-7306. 10523667 . 84838 . 10.1128/mcb.19.11.7782. 11858/00-001M-0000-0015-3C39-0 .