20] Gene expression and thiol redox state

Abstract

Publisher Summary This chapter reviews the different practical approaches that are commonly used to analyze eukaryotic transcription factors whose activation and DNA binding are controlled by the thiol redox status of the cell. It focuses on two well-defined transcription factors: NF−κB (nuclear factor κB) and HSF1, which confer redox state-dependent inducible gene expression. The more frequent form of NF−κB is a heterodimeric complex that contains p50 and p65 polypeptides. Except for B lymphocytes, where it is constitutively active, NF−κB is cytoplasmic in most cells and needs extracellular signals to be activated and to migrate in the nucleus where it binds KB sites (5'-GGGAN/NYYCC-3') on the DNA. Heat shock factor 1 (HSF1) is a transcription factor that regulates the expression of stress (heat shock) genes. HSF1 cytoplasmic activation is mediated by stresses, such as heat shock, or numerous different agents or conditions that generate abnormally folded proteins. Transcription of heat shock (or stress) genes requires the formation of a homotrimeric HSF1 complex that binds to the heat shock promoter element (HSE). HSE is characterized as multiple adjacent and inverse iterations of the 5'-nGAAn-3' motif.