Molecular chaperone that promotes the maturation, structural maintenance and proper regulation of specific target proteins involved for instance in cell cycle control and signal transduction. Undergoes a functional cycle that is linked to its ATPase activity. This cycle probably induces conformational changes in the client proteins, thereby causing their activation. Interacts dynamically with various co-chaperones that modulate its substrate recognition, ATPase cycle and chaperone function. Engages with a range of client protein classes via its interaction with various co-chaperone proteins or complexes, that act as adapters, simultaneously able to interact with the specific client and the central chaperone itself. Recruitment of ATP and co-chaperone followed by client protein forms a functional chaperone. After the completion of the chaperoning process, properly folded client protein and co-chaperone leave HSP90 in an ADP-bound partially open conformation and finally, ADP is released from HSP90 which acquires an open conformation for the next cycle. Apart from its chaperone activity, it also plays a role in the regulation of the transcription machinery. HSP90 and its co-chaperones modulate transcription at least at three different levels. In the first place, they alter the steady-state levels of certain transcription factors in response to various physiological cues. Second, they modulate the activity of certain epigenetic modifiers, such as histone deacetylases or DNA methyl transferases, and thereby respond to the change in the environment. Third, they participate in the eviction of histones from the promoter region of certain genes and thereby turn on gene expression. Antagonizes STUB1-mediated inhibition of TGF-beta signaling via inhibition of STUB1-mediated SMAD3 ubiquitination and degradation. Promotes cell differentiation by chaperoning BIRC2 and thereby protecting from auto-ubiquitination and degradation by the proteasomal machinery. Main chaperone that is involved in the phosphorylation/activation of the STAT1 by chaperoning both JAK2 and PRKCE under heat shock and in turn, activates its own transcription. Belongs to the heat shock protein 90 family. Note: This description may include information from UniProtKB.
Molecular Function: ATP binding; ATP-dependent protein binding; CTP binding; dATP binding; disordered domain specific binding; DNA polymerase binding; double-stranded RNA binding; drug binding; GTP binding; heat shock protein binding; histone deacetylase binding; histone methyltransferase binding; identical protein binding; ion channel binding; kinase binding; nucleotide binding; peptide binding; protein binding; protein dimerization activity; protein homodimerization activity; protein kinase binding; sulfonylurea receptor binding; tau protein binding; ubiquitin protein ligase binding; unfolded protein binding; UTP binding
Biological Process: axon extension; cellular response to interleukin-4; central nervous system neuron axonogenesis; chaperone-mediated protein complex assembly; establishment of cell polarity; negative regulation of apoptotic process; negative regulation of cell cycle arrest; negative regulation of complement-dependent cytotoxicity; negative regulation of neuron apoptotic process; negative regulation of proteasomal protein catabolic process; negative regulation of proteasomal ubiquitin-dependent protein catabolic process; negative regulation of protein metabolic process; negative regulation of transforming growth factor beta activation; placenta development; positive regulation of cell differentiation; positive regulation of cell size; positive regulation of cyclin-dependent protein kinase activity; positive regulation of peptidyl-serine phosphorylation; positive regulation of phosphoprotein phosphatase activity; positive regulation of protein binding; positive regulation of protein kinase B signaling; positive regulation of protein localization to cell surface; positive regulation of protein serine/threonine kinase activity; positive regulation of telomerase activity; positive regulation of transforming growth factor beta receptor signaling pathway; protein folding; regulation of cellular protein localization; regulation of protein ubiquitination; response to organic substance; supramolecular fiber organization; telomerase holoenzyme complex assembly; telomere maintenance via telomerase; virion attachment to host cell