Targeting of a cytosolic protein to the nuclear periphery.
The yeast nuclear envelope protein NSP1 is located at the nuclear pores and mediates its essential function via the carboxy-terminal domain. The passenger protein, cytosolic dihydrofolate reductase from mouse, was fused to the 220 residue long NSP1 carboxy-terminal domain. When expressed in yeast, this chimeric protein was tightly associated with nuclear structures and was localized at the nuclear periphery very similar to authentic NSP1. Furthermore, the DHFR-C-NSP1 fusion protein was able to complement a yeast mutant lacking a functional NSP1 gene showing that DHFR-C-NSP1 fulfils the same basic function as compared to the endogenous NSP1 protein. These data also show that the NSP1 protein is composed of separate functional moieties: a carboxy-terminal domain that is sufficient to mediate the association with the nuclear periphery and an amino-terminal and middle repetitive domain with an as yet unknown function. It is suggested that heptad repeats found in the NSP1 carboxy-terminal domain, which are similar to those found in intermediate filament proteins, are crucial for mediating the association with the nuclear pores.
Hurt
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European Molecular Biology Laboratory, Heidelberg, Federal Republic of Germany.
D000595:Amino Acid Sequence; D000818:Animals; D001692:Biological Transport / Q000502:physiology; D002135:Calcium-Binding Proteins; D005656:Fungal Proteins / Q000737:chemistry / Q000378:metabolism*; D051379:Mice; D008969:Molecular Sequence Data; D009685:Nuclear Envelope / Q000378:metabolism* / Q000502:physiology; D028861:Nuclear Pore Complex Proteins; D009687:Nuclear Proteins / Q000737:chemistry / Q000378:metabolism*; D021382:Protein Sorting Signals / Q000502:physiology; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D012091:Repetitive Sequences, Nucleic Acid; D012441:Saccharomyces cerevisiae / Q000378:metabolism; D029701:Saccharomyces cerevisiae Proteins; D013762:Tetrahydrofolate Dehydrogenase / Q000737:chemistry / Q000378:metabolism*
D002135:Calcium-Binding Proteins; D005656:Fungal Proteins; C062748:NSP1 protein, S cerevisiae; D028861:Nuclear Pore Complex Proteins; D009687:Nuclear Proteins; D021382:Protein Sorting Signals; D011993:Recombinant Fusion Proteins; D029701:Saccharomyces cerevisiae Proteins; D013762:Tetrahydrofolate Dehydrogenase