Four heat shock factor proteins (HSFs) have been identified in vertebrates (HSF1-4) []. HSF2 is localised to the cytoplasm duringnormal growth and moves to the nucleus upon activation [], where it specifically binds heat shock promoter elements (HSE) and activates transcription. HSF2 may not be directly involved in the stress response, but rather in cell differentiation and development [, ]. HSF1 and HSF2 can form heterotrimers, which could be a mechanism regulating transcription [].
This group represents protein kinase C (KPC), including zeta/iota types from mammals, protein kinase C-like 3 from round worms []and atypical protein kinase C (aPKC) from fruit flies []. Protein kinase C iota type (PRKCI) is a calcium- and diacylglycerol-independent serine/ threonine-protein kinase that plays a general protective role against apoptotic stimuli, is involved in NF-kappa-B activation, cell survival, differentiation and polarity, and contributes to the regulation of microtubule dynamics in the early secretory pathway [, , ]. It is an indirect co-regulator of the stress-activated transcription factor HSF1 and the heat shock response []. It has been linked to cancers [, ].Protein kinase C zeta type is a calcium- and diacylglycerol-independent serine/threonine-protein kinase that functions in phosphatidylinositol 3-kinase (PI3K) pathway and mitogen-activated protein (MAP) kinase cascade, and is involved in NF-kappa-B activation, mitogenic signaling, cell proliferation, cell polarity, inflammatory response and maintenance of long-term potentiation (LTP) [].
