%0 Journal Article
%T Proliferation/quiescence: the controversial "aller-retour"
%A Bertrand Daignan-Fornier
%A Isabelle Sagot
%J Cell Division
%D 2011
%I BioMed Central
%R 10.1186/1747-1028-6-10
%X Quiescence is the most common cellular state on earth. While it is relatively easy to describe a proliferating cell, defining a quiescent cell is rather difficult. A commonly accepted, yet highly operational, definition of quiescence is "a reversible absence of proliferation". Consequently, a cell that is not dividing but eventually will when conditions become appropriate, is considered as a bona fide quiescent cell. But this definition is rather vague and probably encompasses various cellular situations. Therefore, instead of a single quiescent state, one can imagine that there may be distinct quiescent states depending on the cell's history before entry into quiescence, and/or depending on the time spent in quiescence (early quiescence, deep quiescence..., see Figure 1). This raises the delicate question of the existence of a quiescence "program". In other words, does quiescence result from a dedicated gene expression pattern that commits cells to the quiescent state or is quiescence an ultimate form of slow growth which would be a passive consequence of a cell's adaptation to unfavorable external conditions?One major problem for studying quiescence comes from the fact that in multi-cellular organisms, environmental signals that control quiescence emanate from the entire organism - conditions that are difficult to reproduce in a lab. By contrast, in single cell eukaryotes like budding yeast, quiescence entry and exit are solely conditioned by nutrient availability. Using this model, the nature of proliferation/quiescence transitions has recently been revisited.Budding yeast is THE model in which genetics has proven its power, and not surprisingly, using this organism, several genetic approaches have been developed in order to identify a dedicated mechanism that drives cells into quiescence. Many mutants were found to be specifically sensitive to one nutrient limitation [1-5], but only very few of them died upon all the starvation conditions tested [1,2]. At the pr
%U http://www.celldiv.com/content/6/1/10