Specific interactions of the autoantigen L7 with multi-zinc finger protein ZNF7 and ribosomal protein S7.
The eucaryotic protein L7, which associates with the large subunit of ribosomes, has been shown to be a major autoantigen in systemic autoimmune arthritis. The N terminus carries a sequence motif that is similar to the leucine zipper domain of eucaryotic transcription factors. This domain promotes the homodimerization of protein L7 through alpha-helical coiled-coil formation and binds to distinct mRNAs, thereby inhibiting their cell-free translation. Using a yeast two-hybrid selection, we have identified from a Jurkat T lymphoma cDNA library ribosomal protein S7 and the multi-zinc finger protein ZNF7 as proteins that interact with protein L7. A fragment of L7 carrying the leucine zipper-like domain is fully sufficient to mediate these interactions. Their potential biological significance is indicated by low apparent dissociation constants of S7-L7 (15 x 10(-9) M) and, respectively, ZNF7-L7 (2 x 10(-9) M) complexes and co-immunoprecipitation of proteins S7, ZNF7, and L7 from a cell lysate with an anti-L7 antibody. We also show that ZNF7-like L7 and S7 can exist in a ribosome-bound form. This study provides further evidence suggesting that L7 is involved in translational regulation through interactions with components of the translational apparatus.
Witte
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Fakultät für Biologie, Universität Konstanz, Postfach 5560, 78434 Konstanz, Germany. stephan.witte@uni-konstanz.de
Krawinkel
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D004268:DNA-Binding Proteins / Q000378:metabolism*; D019281:Dimerization; D006801:Humans; D019169:Jurkat Cells; D051741:Kruppel-Like Transcription Factors; D016350:Leucine Zippers; D012269:Ribosomal Proteins / Q000378:metabolism*; D012270:Ribosomes / Q000378:metabolism; D016335:Zinc Fingers
D004268:DNA-Binding Proteins; D051741:Kruppel-Like Transcription Factors; C053634:RPL7 protein, human; D012269:Ribosomal Proteins; C094470:ZNF7 protein, human; C037442:ribosomal protein S7