E3 ubiquitin-protein ligase CHIP (STUB1)

E3 ubiquitin-protein ligase which targets misfolded chaperone substrates towards proteasomal degradation. Collaborates with ATXN3 in the degradation of misfolded chaperone substrates: ATXN3 restricting the length of ubiquitin chain attached to STUB1/CHIP substrates and preventing further chain extension.

Ubiquitinates NOS1 in concert with Hsp70 and Hsp40. Modulates the activity of many chaperone complexes, including Hsp70, Hsc70 and Hsp90.