RNA polymerase II pausing and transcriptional regulation of the HSP70 expression

Heat-shock proteins (HSPs) belong to the chaperone protein family whose expression is induced by different stresses including heat-shock. In response to the extracellular or intrinsic stimuli and stresses, HSPs play important roles in the maintenance of cellular homeostasis. HSP70, a major HSP protein (molecular weight, 70 KDa), regulates diverse cellular pathways including protein quality control, translation, immune response, and cancer survival. As a critical cellular defense system to minimize damages from cellular stresses, HSP70 expression and transcriptional activation are rapidly regulated, mainly through the action of a transcription activator, Heat shock factor 1 (HSF1). Eukaryotic HSP70 genes are well-characterized; they utilize a transcriptional mechanism termed as RNA polymerase II (Pol II) promoter-proximal pausing. Pol II promoter-proximal pausing enables synchronized gene expression in a number of mammalian protein-coding and non-protein coding genes upon the reception of gene activating signals. In particular, Drosophila and human HSP70 genes serve as a bona fide model system to understand the mechanisms of Pol II pausing and pause release. In this review, we will discuss HSP70 transcription and the newly discovered mechanisms that regulate HSP70 gene expression.