A decade's worth of Ran

Abstract

The Small GTPase RanEdited by Mark Rush and Peter D'Eustachio.Kluwer Academic Publishers, 2001.?145.00 /$130.00/£91.00 (214 pages)ISBN 0 7923 7510 6View Large Image | Download PowerPoint Slide Since its discovery in 1990, the small Ras-related GTPase Ran has been the focus of extensive research in laboratories world wide. Its function has been studied in a variety of model systems, including mammalian cells, Xenopus laevis egg extracts, fission and bakers’ yeast. While early studies implicated Ran and its key regulators (the Ran GTPase-activating protein and the Ran GDP–GTP exchange factor) in a plethora of nuclear functions, including RNA processing, DNA replication, chromosome segregation and cell-cycle regulation, Ran was soon shown to be a key player in nucleocytoplasmic transport. In fact, Ran is involved, both directly and indirectly, in the translocation of most, if not all, macromolecules through nuclear pore complexes. Exciting findings during the past two years, however, put the spotlight back on Ran's putative role in the cell cycle. Although many questions remain to be solved, it is now well established that both formation of the mitotic spindle and reformation of the nuclear envelope respond to the Ran-GTPase cycle.With The Small GTPase Ran, Mark Rush and Peter D'Eustachio, both of whom were involved in the original discovery of Ran, present a stimulating and interesting anthology that covers the first decade of Ran research. Aimed at the specialist rather than at students, this book does not provide a simple, unified picture of Ran's molecular mechanisms. Rather, it allows distinguished researchers to present their personal view on Ran function and significance. In areas where the field has come to some consensus, a single chapter suffices (e.g. for nuclear protein import); in more recent and consequently less well-understood areas, overlapping chapters by different authors are presented.A clear and concise preface by the editors summarizes well-established facts and models and points out some of the controversial issues that remain to be solved. This introduction is followed by ten chapters covering the role of Ran in nuclear import (Chapter 1), nuclear export of proteins and RNA (Chapters 2–4), and mitosis (Chapters 5–8), and the book provides ample information on the biochemistry (Chapter 9) and structure of Ran and its interactors (Chapter 10). Two chapters are specifically devoted to the function of Ran in budding yeast (with a focus on RNA processing and export; Chapter 3) and fission yeast (multiple roles of Ran; Chapter 7). This distinction between the role of Ran in yeast and higher Eukarya is necessary despite the high conservation of the Ran GTPase cycle throughout the eukaryotic kingdom. Significant differences exist, for example, in the dimensions and composition of the nuclear pore complex, and functional homologs are not yet known for all components of the import/export pathways. Moreover, vertebrate, but not yeast, cells undergo nuclear envelope breakdown during mitosis, and models that have been developed for Ran's role in vertebrate spindle formation are not easily transferable to spindle formation in yeast.Each chapter can be independently read, which allows for a quick overview on a particular subject, but which also results in a fair bit of redundancy. As a whole, the book also serves as an excellent reference source because virtually all available data on Ran are covered somewhere in the book. In general, the chapters are very well written and provide valuable background information (e.g. on RNA processing or on microtubule dynamics). Highly variable, however, is the style of the chapters. Some provide a scholarly and balanced overview on a particular subject and will be helpful for students and experts alike. Others present more biased, personal views and neglect to discuss conflicting data from the literature. Consequently, upon reading several chapters on one subject, one stumbles occasionally over outright contradictory statements regarding the mechanism of a pathway or the function of a particular protein. While this provides ‘food for thought’ for experts in the field, it is probably rather confusing for the uninitiated readership. Here, it would have been helpful if the editors had expanded their preface to point out more specifically areas of conflict and controversy. Finally, a table listing all known Ran interactors with their yeast and vertebrate names and, where possible, their function would have been quite handy – as the editors point out in their preface, the nomenclature is confusing even for workers in the field.In conclusion, I found this book an enjoyable and instructive read and will certainly use it often as a reference in the future. While it might be a bit too specialized for students and outsiders to the field, its intention to provide specialists with a summary of recent and past research on Ran is very well met.