Mechanism and a Peptide Motif for Targeting Peripheral Proteins to the Yeast Inner Nuclear Membrane |
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| Authors: | Tsung-Po Lai Karen A Stauffer Athulaprabha Murthi Hussam H Shaheen Gang Peng Nancy C Martin Anita K Hopper |
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| Institution: | Department of Molecular Genetics, The Ohio State University, Columbus, OH 43210, USA; Department of Biochemistry and Molecular Biology, H171, Pennsylvania State University College of Medicine, Hershey, PA 17033, USA; Department of Biochemistry, University of Louisville School of Medicine, Louisville, KY 40292, USA; Current address: Medical Communications Group, Wolters Kluwer Health, 770 Township Line Road, Suite 300, Yardley, PA 19067, USA; Current address: National Institute for Allergy and Infectious Disease, National Institutes of Health, Bethesda, MD 20892, USA; Current address: Merck and Co., Glycofi Department, 21 Lafayette Street, Suite 200, Lebanon, NH 03766, USA; Current address: 1012 Mingdao Building, Institute of Brain Science, Fudan University, 138 Yixueyuan Road, Shanghai 200032, China |
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| Abstract: | Trm1 is a tRNA specific m22G methyltransferase shared by nuclei and mitochondria in Saccharomyces cerevisiae . In nuclei, Trm1 is peripherally associated with the inner nuclear membrane (INM). We investigated the mechanism delivering/tethering Trm1 to the INM. Analyses of mutations of the Ran pathway and nuclear pore components showed that Trm1 accesses the nucleoplasm via the classical nuclear import pathway. We identified a Trm1 cis-acting sequence sufficient to target passenger proteins to the INM. Detailed mutagenesis of this region uncovered specific amino acids necessary for authentic Trm1 to locate at the INM. The INM information is contained within a sequence of less than 20 amino acids, defining the first motif for addressing a peripheral protein to this important subnuclear location. The combined studies provide a multi-step process to direct Trm1 to the INM: (i) translation in the cytoplasm; (ii) Ran-dependent import into the nucleoplasm; and (iii) redistribution from the nucleoplasm to the INM via the INM motif. Furthermore, we demonstrate that the Trm1 mitochondrial targeting and nuclear localization signals are in competition with each other, as Trm1 becomes mitochondrial if prevented from entering the nucleus. |
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| Keywords: | inner nuclear membrane mitochondrial location nucleus organization targeting motif |
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