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J. Biol. Chem., Vol. 280, Issue 47, 39067-39076, November 25, 2005

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Atg19p Ubiquitination and the Cytoplasm to Vacuole Trafficking Pathway in Yeast^*

Bonnie K. Baxter, Hagai Abeliovich¶, Xin Zhang||, Aline G. Stirling, Alma L. Burlingame||, and David S. Goldfarb1

From the Department of Biology, University of Rochester, Rochester, New York 14627, ^¶Faculty of Agriculture, Hebrew University of Jerusalem, Rehovot, Israel 78100, Department of Biology, Hobart and William Smith Colleges, Geneva, New York 14456, and the ^||Department of Pharmaceutical Chemistry and Mass Spectrometry Facility, University of California, San Francisco, California 94143

The cytoplasm to vacuole (Cvt) trafficking pathway in S. cerevisiae is a constitutive biosynthetic pathway required for the transport of two vacuolar enzymes, aminopeptidase I (Ape1p) and -mannosidase (Ams1p), to the vacuole. Ape1p and Ams1p bind to their receptor, Atg19p, in the cytosol to form a Cvt complex, which then associates with a membrane structure that envelops the complex before fusing with the vacuolar membrane. Ubiquitin-like modifications are required for both Cvt and macroautophagy, but no role for ubiquitin itself has been described. Here, we show that the deubiquitinating enzyme Ubp3p interacts with Atg19p. Moreover, Atg19p is ubiquitinated in vivo, and Atg19p-ubiquitin conjugates accumulate in cells lacking either Ubp3p or its cofactor, Bre5p. Deletion of UBP3 also leads to decreased targeting of Ape1p to the vacuole. Atg19p is ubiquitinated on two lysine residues, Lys²¹³ and Lys²¹⁶, which, when mutated, reduce the interaction of Atg19p with Ape1p. These results suggest that both ubiquitination and deubiquitination of Atg19p are required for its full function.

Received for publication, July 22, 2005 , and in revised form, September 9, 2005.

^* This work was supported by a Merck/AAAS and Perkins Foundation grant (to A. G. S.), a Hobart and William Smith Colleges faculty research grant (to B. K. B.), National Institutes of Health (NIH) National Center for Research Resources Grants RR 01614 and RR 12961 (to A. L. B.) Israel Science Foundation Grant 496/03 (to H. A.), and National Science Foundation Grant MCB 0110972 and NIH Grant GM067838 (to D. S. G.). The costs of publication of this article were defrayed in part by the payment of page charges. This article must therefore be hereby marked "advertisement" in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.

¹ To whom correspondence should be addressed: Dept. of Biology, University of Rochester, Rochester, NY 14627. Tel.: 585-275-3890; Fax: 585-275-2070; E-mail: dasg{at}mail.rochester.edu.

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