Annu. Rev. Cell Dev. Biol. 2001. 17:297–310 Copyright c  2001 by Annual Reviews. All rights reserved RNP LOCALIZATION AND TRANSPORT IN YEAST Pascal Chartrand and Robert H. Singer Departments of Anatomy and Structural Biology, and Cell Biology, Albert-Einstein College of Medicine, Bronx, New York 10461; e-mail: chartran@aecom.yu.edu; rhsinger@aecom.yu.edu Roy M. Long Department of Microbiology and Molecular Genetics, Medical College of Wisconsin, Milwaukee, Wisconsin 53226-0509; e-mail: rlong@mcw.edu Key Words ASH1 mRNA, RNA localization, She proteins, locasome, myosin ■ Abstract The localization of mRNAs is used by various types of polarized cells to locally translate specific proteins, which restricts their distribution to a particular sub-region of the cytoplasm. This mechanism of protein sorting is involved in major biological processes such as asymmetric cell division, oogenesis, cellular motility, and synapse formation. With the finding of localized mRNAs in the yeast Saccharomyces cerevisiae, it is now possible to benefit from the powerful yeast laboratory tools to explore the molecular basis of RNA localization. Because mRNA transport and lo- calization in yeast share many features with RNA localization in higher eukaryotes, including the formation of a large ribonucleoprotein (RNP) localization complex, the requirement of a polarized cytoskeleton and molecular motors, and the role of nuclear RNA-binding proteins in cytoplasmic localization, the yeast can be used as a paradigm for unraveling the molecular aspects of this process. This review summarizes the current knowledge on RNP transport and localization in yeast. CONTENTS INTRODUCTION ..................................................... 298 LOCALIZED RNA IN YEAST: ROLES AND FUNCTIONS ................... 299 ASH1 ............................................................. 299 IST2 .............................................................. 299 ATM1 ............................................................. 300 CIS-ACTING ELEMENTS THAT TARGET AN RNA TO ITS SPECIFIC LOCATION ................................................ 300 ASH1 mRNA ....................................................... 300 IST2 mRNA ........................................................ 301 ATM1 mRNA ....................................................... 301 TRANS-ACTING FACTORS INVOLVED IN RNA LOCALIZATION ............ 301 Myo4p/She1p ....................................................... 301 1081-0706/01/1115-0297$14.00 297