TY - JOUR
T1 - A conserved biogenesis pathway for nucleoporins
T2 - Proteolytic processing of a 186-kilodalton precursor generates Nup98 and the novel nucleoporin, Nup96
AU - Fontoura, Beatriz M A
AU - Blobel, Günter
AU - Matunis, Michael J.
PY - 1999/3/22
Y1 - 1999/3/22
N2 - The mammalian nuclear pore complex (NPC) is comprised of ~50 unique proteins, collectively known as nucleoporins. Through fractionation of rat liver nuclei, we have isolated >30 potentially novel nucleoporins and have begun a systematic characterization of these proteins. Here, we present the characterization of Nup96, a novel nucleoporin with a predicted molecular mass of 96 kD. Nup96 is generated through an unusual biogenesis pathway that involves synthesis of a 186-kD precursor protein. Proteolytic cleavage of the precursor yields two nucleoporins: Nup98, a previously characterized GLFG- repeat containing nucleoporin, and Nup96. Mutational and functional analyses demonstrate that both the Nup98-Nup96 precursor and the previously characterized Nup98 (synthesized independently from an alternatively spliced mRNA) are proteolytically cleaved in vivo. This biogenesis pathway for Nup98 and Nup96 is evolutionarily conserved, as the putative Saccharomyces cerevisiae homologues, N-Nup145p and C-Nup145p, are also produced through proteolytic cleavage of a precursor protein. Using immunoelectron microscopy, Nup96 was localized to the nucleoplasmic side of the NPC, at or near the nucleoplasmic basket. The correct targeting of both Nup96 and Nup98 to the nucleoplasmic side of the NPC was found to be dependent on proteolytic cleavage, suggesting that the cleavage process may regulate NPC assembly. Finally, by biochemical fractionation, a complex containing Nup96, Nup107, and at least two Sec13-related proteins was identified, revealing that a major sub-complex of the NPC is conserved between yeast and mammals.
AB - The mammalian nuclear pore complex (NPC) is comprised of ~50 unique proteins, collectively known as nucleoporins. Through fractionation of rat liver nuclei, we have isolated >30 potentially novel nucleoporins and have begun a systematic characterization of these proteins. Here, we present the characterization of Nup96, a novel nucleoporin with a predicted molecular mass of 96 kD. Nup96 is generated through an unusual biogenesis pathway that involves synthesis of a 186-kD precursor protein. Proteolytic cleavage of the precursor yields two nucleoporins: Nup98, a previously characterized GLFG- repeat containing nucleoporin, and Nup96. Mutational and functional analyses demonstrate that both the Nup98-Nup96 precursor and the previously characterized Nup98 (synthesized independently from an alternatively spliced mRNA) are proteolytically cleaved in vivo. This biogenesis pathway for Nup98 and Nup96 is evolutionarily conserved, as the putative Saccharomyces cerevisiae homologues, N-Nup145p and C-Nup145p, are also produced through proteolytic cleavage of a precursor protein. Using immunoelectron microscopy, Nup96 was localized to the nucleoplasmic side of the NPC, at or near the nucleoplasmic basket. The correct targeting of both Nup96 and Nup98 to the nucleoplasmic side of the NPC was found to be dependent on proteolytic cleavage, suggesting that the cleavage process may regulate NPC assembly. Finally, by biochemical fractionation, a complex containing Nup96, Nup107, and at least two Sec13-related proteins was identified, revealing that a major sub-complex of the NPC is conserved between yeast and mammals.
KW - Nuclear pore complex
KW - Nucleocytoplasmic transport
KW - Nucleoporin
KW - Proteolytic cleavage
KW - RNA export
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U2 - 10.1083/jcb.144.6.1097
DO - 10.1083/jcb.144.6.1097
M3 - Article
C2 - 10087256
AN - SCOPUS:0033594084
SN - 0021-9525
VL - 144
SP - 1097
EP - 1112
JO - Journal of Cell Biology
JF - Journal of Cell Biology
IS - 6
ER -