Formation Mechanism and Cellular Functions of Nuclear Stress Bodies Induced by Heat Stress

Mammal possesses mechanisms that respond to environmental stresses, including heat, oxidation, radiation. Stress responses include cell death induction mechanism such as apoptosis and stress accommodation mechanism for survival. One of a major stress accommodation mechanism is formation of stress granules (SGs) and nuclear stress bodies (nSBs). SGs and nSBs, which are constituted by many proteins and RNAs, are reversible intracellular structures formed only when cells are exposed to environmental stresses. SGs, formed in the cytoplasm, have been found in a wide range of eukaryotes from yeast to humans. Intriguingly, nSBs, formed in the nucleus, have been found only in human cells. In this review, we focus on nSBs. nSBs were discovered in heat-stressed cells in 1989, and then many proteins and RNAs have been identified. Major components of nSBs are heat shock transcription factor family, splicing factors and non-coding RNAs (Satellite III RNA and initiator/elongator tRNA). Recently, many researchers have reported the formation mechanism of nSBs, however cellular functions of nSBs remain unclear. In this review, we introduce the basic researches focusing on the nSBs formation mechanism and cellular functions of nSBs constitution factors.