Exportin 7 defines a novel general nuclear export pathway

Abstract

Most transport pathways between cell nucleus and cytoplasm are mediated by nuclear transport receptors of the importin b family. These receptors are in continuous circulation between the two compartments and transfer cargo molecules from one side of the nuclear envelope to the other. RanBP16 is a family member from higher eukaryotes of so far unknown function. We now show that it exports p50RhoGAP from the nucleus and thereby confines this activity to the cytoplasm. It also accounts for nuclear exclusion of 14-3-3r, which in turn is known to anchor, for example, cyclin-dependent kinases in the cytoplasm. Our data further suggest that RanBP16 exports several additional cargoes. It thus appears to be a nuclear export mediator with broad substrate specificity and we will therefore refer to it as exportin 7 (Exp7). Finally, we demonstrate that Exp7-dependent nuclear export signals differ fundamentally from the leucine-rich, CRM1-dependent ones: First, they are not just short linear sequences, but instead include folded motifs. Second, basic residues are critical for Exp7 recruitment.

Non-random subcellular distribution of variant EKLF in erythroid cells

“…Coupled to this is our inability to efficiently inhibit endogenous or exogenous EKLF export by LMB. CRM-independent export mechanisms, although not common, have been observed before [44][45][46].…”

NSUN 3 and ABH 1 modify the wobble position of mt‐t RNA Met to expand codon recognition in mitochondrial translation

“…The coding sequences of human NSUN3, ABH1 or FTO were cloned into a pQE80 derivative encoding an N‐terminal His 14 ‐MBP‐tag (Weis et al , 2014) and the CDS of MTIF2 or TUFM into a pQE80 derivative encoding a C‐terminal His 10 ‐tag (Mingot et al , 2004). The ABH1 D233A and R233A, and NSUN3 C265A mutants were generated by site‐directed mutagenesis (Haag et al , 2015b).…”

STRADα Regulates LKB1 Localization by Blocking Access to Importin-α, and by Association with Crm1 and Exportin-7

“…LMB inhibited CRM1 binding to STRAD␣, but not that of exportin7 ( Figure 7A). The specificity of this interaction was highlighted by the fact that the two closest mammalian homologues of exportin7, exportin4 and RanBP17, showed no Ran-dependent binding to STRAD␣ (data not shown) (Koch et al, 2000;Kutay et al, 2000;Mingot et al, 2004).…”

“…LMB inhibited CRM1 binding to STRAD␣, but not that of exportin7 ( Figure 7A). The specificity of this interaction was highlighted by the fact that the two closest mammalian homologues of exportin7, exportin4 and RanBP17, showed no Ran-dependent binding to STRAD␣ (data not shown) (Koch et al, 2000;Kutay et al, 2000;Mingot et al, 2004).The p50RhoGAP, 14-3-3s, and eIF1 are all cargoes for exportin7, but they share no obvious function, structure, or sequence similarities, and the nuclear export signal for exportin7 has not been definitively established. Nonetheless, it is distinct from the short, leucine-rich NES recognized by CRM1, and at least for p50RhoGAP and eIF1 contains positively charged residues (Mingot et al, 2004).…”

“…An examination of the N-terminus of STRAD␣ revealed a short region containing basic residues. Because it was previously reported that exportin7 binding to eIF1 requires positively charged residues (Mingot et al, 2004), we asked whether the basic residues in STRAD␣ participate in exportin7 binding. Therefore, we deleted the first 19 amino acids of STRAD␣ up to, but excluding, the first leucine-rich NES.…”