CRM1-dependent nuclear export and dimerization with hMSH5 contribute to the regulation of hMSH4 subcellular localization.
MSH4 and MSH5 are members of the MutS homolog family, a conserved group of proteins involved in DNA mismatch correction and homologous recombination. Although several studies have provided compelling evidences suggesting that MSH4 and MSH5 could act together in early and late stages of meiotic recombination, their precise roles are poorly understood and recent findings suggest that the human MSH4 protein may also exert a cytoplasmic function. Here we show that MSH4 is present in the cytoplasm and the nucleus of both testicular cells and transfected somatic cells. Confocal studies on transfected cells provide the first evidence that the subcellular localization of MSH4 is regulated, at least in part, by an active nuclear export pathway dependent on the exportin CRM1. We used deletion mapping and mutagenesis to define two functional nuclear export sequences within the C-terminal part of hMSH4 that mediate nuclear export through the CRM1 pathway. Our results suggest that CRM1 is also involved in MSH5 nuclear export. In addition, we demonstrate that dimerization of MSH4 and MSH5 facilitates their nuclear localization suggesting that dimerization may regulate the intracellular trafficking of these proteins. Our findings suggest that nucleocytoplasmic traffic may constitute a regulatory mechanism for MSH4 and MSH5 functions.
Neyton
Sophie
S
Equipe M3R, UMR 6543, Université de Nice Sophia-Antipolis, CNRS, Faculté de Médecine, Avenue de Valombrose 06107, Nice Cedex 2, France.
Lespinasse
Françoise
F
Lahaye
François
F
Staccini
Pascal
P
Paquis-Flucklinger
Véronique
V
Santucci-Darmanin
Sabine
S
D021581:Active Transport, Cell Nucleus / Q000187:drug effects; D000595:Amino Acid Sequence; D000818:Animals; D018797:Cell Cycle Proteins / Q000032:analysis / Q000235:genetics / Q000378:metabolism*; D002467:Cell Nucleus / Q000737:chemistry / Q000378:metabolism; D003593:Cytoplasm / Q000737:chemistry / Q000378:metabolism; D019281:Dimerization; D005231:Fatty Acids, Unsaturated / Q000494:pharmacology; D006801:Humans; D028884:Karyopherins / Q000235:genetics / Q000378:metabolism*; D008297:Male; D051379:Mice; D008815:Mice, Inbred Strains; D008817:Mice, Mutant Strains; D008969:Molecular Sequence Data; D049790:Nuclear Export Signals / Q000235:genetics; D017434:Protein Structure, Tertiary; D018160:Receptors, Cytoplasmic and Nuclear / Q000235:genetics / Q000378:metabolism*; D013737:Testis / Q000737:chemistry / Q000378:metabolism*; D000097606:Exportin 1 Protein
D018797:Cell Cycle Proteins; D005231:Fatty Acids, Unsaturated; D028884:Karyopherins; D049790:Nuclear Export Signals; D018160:Receptors, Cytoplasmic and Nuclear; D000097606:Exportin 1 Protein; C409221:MSH4 protein, human; C118481:MSH5 protein, human; C038753:leptomycin B