Heat shock constitutive gene expression

Beere, H.M., Morimoto, R.I., Hickman, J.A. (1993). Investigations of mechanisms of drug-induced changes in gene expression N methylformamide-induced changes in synthesis of the M(r) 72,000 constitutive heat shock protein during commitment of HL-60 cells to granulocyte differentiation. Cancer Res. 53, 3034—3039. 

In virtually all organisms, enhanced synthesis of heat shock proteins (HSPs) occurs in response to environmental, chemical, and physiological stresses. Some members of the evolutionarily conserved HSP gene family are constitutively expressed and function as molecular chaperones. It has been demonstrated that HSP induction results primarily from the activation of a heat shock transcription factor (HSF) with subsequent binding to heat shock response DNA elements (HSEs) in the enhancer regions of the HSP genes157. Heat shock responses in fish have been recently reviewed by Basu et al.15 and will be discussed in another chapter of this volume, so we will primarily limit our discussions to heat shock responses in zebrafish. 

Zafarullah, M., J. Wisniewski, N.W. Shworak, S. Schieman, S. Misra and L. Gedamu. Molecular cloning and characterization of a constitutively expressed heat-shock-cognate hsc71 gene from rainbow trout. Eur. J. Biochem. 204 893-900, 1992. 

Hemeoxygenase-1 (HOI) and hemeoxygenase-2 (H02), members of the stress protein superfamily, are deployed in the ER. Three HO isoforms (HOI, H02, and H03) have been identified. HOI is a 32 kDa heat-shock protein with a low expression in brain that increases after heat shock. H02 is a constitutively synthesized 36 kDa protein that has its major activity in the brain (Trakshel et al., 1988). H03 is related to H02 but is the product of a different gene. They catalyze the oxidative degradation of pro-oxidant metalloporphyrins such as heme (potential pro-oxidant) to biliverdin, which is subsequently converted to bilirubin (potential antioxidant) by biliverdin reductase and carbon monoxide, finally releasing iron (pro-oxidant Ewing andMaines, 1991). 

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