What are the characteristics of quiescent cells?

Quiescence refers to the cellular state in which a cell is nondividing and not active in the cell cycle, but maintains the ability to divide upon appropriate cues. Quiescent cells are highly diverse, and exist in different locations throughout the body. The entry of cells into a quiescent state allows them to survive in a nondividing state for extended periods of time and to enable mechanisms to protect themselves from damage. They each have distinct roles and are activated by various types of signals. However, all quiescent cells must be able to exist in a nondividing state without altering their ability to proliferate at a later time. Quiescent cells have decreased metabolic activity in comparison to actively dividing cells; they require less energy and resources to sustain their cellular functions since they are not synthesizing DNA or undergoing cell division. Their decreased metabolic activity is characterized by a decrease in glucose uptake glycolysis, reduced translation rates, and activation of autophagy in order to provide nutrients for survival. Thus, quiescent cells also have reduced rates of RNA and protein synthesis. Additionally, quiescent cells exhibit reduced size compared to actively dividing cells. This is due to their decreased metabolic activity as well as the reduced synthesis of macromolecules. Quiescent cells also exhibit reduced transcription of certain genes and increased expression of others. These changes include down-regulation of genes corresponding with cell cycle progression and up-regulation of genes associated with tumor suppressors.