ABSTRACT
The survival motor neurons (smn) gene in mice is essential for embryonic viability. In humans, mutation of the telomeric copy of the SMN1 gene causes spinal muscular atrophy, an autosomal recessive disease. Here we report that the SMN protein interacts with the zinc-finger protein ZPR1 and that these proteins colocalize in small subnuclear structures, including gems and Cajal bodies. SMN and ZPR1 redistribute from the cytoplasm to the nucleus in response to serum. This process is disrupted in cells from patients with Werdnig-Hoffman syndrome (spinal muscular atrophy type I) that have SMN1 mutations. Similarly, decreased ZPR1 expression prevents SMN localization to nuclear bodies. Our data show that ZPR1 is required for the localization of SMN in nuclear bodies.
Subject(s)
Carrier Proteins/metabolism , Muscular Atrophy, Spinal/metabolism , Nerve Tissue Proteins/metabolism , Zinc Fingers , Alternative Splicing , Animals , COS Cells , Carrier Proteins/genetics , Cell Nucleus/metabolism , Chlorocebus aethiops , Cyclic AMP Response Element-Binding Protein , Cytoplasm/metabolism , HeLa Cells , Humans , Membrane Transport Proteins , Nerve Tissue Proteins/genetics , RNA Precursors , RNA-Binding Proteins , SMN Complex Proteins , Survival of Motor Neuron 1 ProteinABSTRACT
The zinc finger protein ZPR1 is present in the cytoplasm of quiescent mammalian cells and translocates to the nucleus upon treatment with mitogens, including epidermal growth factor (EGF). Homologues of ZPR1 were identified in yeast and mammals. These ZPR1 proteins bind to eukaryotic translation elongation factor-1alpha (eEF-1alpha). Studies of mammalian cells demonstrated that EGF treatment induces the interaction of ZPR1 with eEF-1alpha and the redistribution of both proteins to the nucleus. In the yeast Saccharomyces cerevisiae, genetic analysis demonstrated that ZPR1 is an essential gene. Deletion analysis demonstrated that the NH2-terminal region of ZPR1 is required for normal growth and that the COOH-terminal region was essential for viability in S. cerevisiae. The yeast ZPR1 protein redistributes from the cytoplasm to the nucleus in response to nutrient stimulation. Disruption of the binding of ZPR1 to eEF-1alpha by mutational analysis resulted in an accumulation of cells in the G2/M phase of cell cycle and defective growth. Reconstitution of the ZPR1 interaction with eEF-1alpha restored normal growth. We conclude that ZPR1 is essential for cell viability and that its interaction with eEF-1alpha contributes to normal cellular proliferation.
Subject(s)
Carrier Proteins/genetics , Carrier Proteins/metabolism , Cell Cycle/physiology , Peptide Elongation Factors/metabolism , Saccharomyces cerevisiae Proteins , Saccharomyces cerevisiae/genetics , Saccharomyces cerevisiae/physiology , Amino Acid Sequence , Animals , COS Cells , Carrier Proteins/chemistry , Cell Division , Cell Line , Consensus Sequence , Fungal Proteins/genetics , Fungal Proteins/metabolism , G2 Phase , Gene Deletion , Genes, Fungal , Genotype , Humans , Intracellular Signaling Peptides and Proteins , Mammals , Membrane Transport Proteins , Mice , Mitosis , Molecular Sequence Data , Peptide Elongation Factor 1 , Peptide Elongation Factors/isolation & purification , Recombinant Proteins/chemistry , Recombinant Proteins/metabolism , Restriction Mapping , Saccharomyces cerevisiae/cytology , Schizosaccharomyces/genetics , Sequence Alignment , Sequence Homology, Amino Acid , Zinc FingersABSTRACT
The zinc finger protein ZPR1 translocates from the cytoplasm to the nucleus after treatment of cells with mitogens. The function of nuclear ZPR1 has not been defined. Here we demonstrate that ZPR1 accumulates in the nucleolus of proliferating cells. The role of ZPR1 was examined using a gene disruption strategy. Cells lacking ZPR1 are not viable. Biochemical analysis demonstrated that the loss of ZPR1 caused disruption of nucleolar function, including preribosomal RNA expression. These data establish ZPR1 as an essential protein that is required for normal nucleolar function in proliferating cells.
