Escape from Cellular Quiescence
Quiescent: From Latin quies, referring to a state of being at rest, dormant, inactive, quiet, still (Merriam-Webster, 2009, Online Dictionary: http://www.merriam-webster.com/dictionary/quiescent). This term refers to a state of dormancy as opposed to a proliferative state. However, quiescent cells are in any other regard metabolically active. In many tissues with relative fast cell renewal rates the primary function of a small group of undifferentiated cells is limited to self-renewal (stem cells). These cells remain quiescent most of the time dividing only occasionally. In other tissues, key cell types perform fundamental tissue functions while remaining quiescent. Both stem cells and cells from tissues that renew via simple duplication can remain quiescent for long periods of time while retaining the capacity to re-enter the cell cycle. This chapter will discuss the mechanisms emerging as responsible for the maintenance of quiescence as well as those pathways that mediate quiescence entry and exit. We will also review signaling pathways deregulated during infection by Simian Virus 40 (SV40) and oncogenic transformation, which result in unscheduled exit from quiescence into the cell cycle, with focus on SV40 small t antigen.
KeywordsQuiescent Cell Mitogenic Stimulation Normal Human Fibroblast Cell Cycle Exit Pocket Protein
We thank Manuel Serrano, David G. Johnson, Alison Kurimchak, and Judit Garriga for critically reading this manuscript and helpful suggestions. Work in this lab has been supported by a grant project under CA095569 and a Career Development Award (K02 AI01823) to XG of the National Institutes of Health.
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