hsp70-interacting

E3 Ubiquitin-Protein Ligase CHIP is a cytoplasmic protein. CHIP is highly expressed in skeletal muscle, heart, pancreas, brain and placenta. CHIP interacts with the molecular chaperones Hsc70-Hsp70 and Hsp90 through its TPR domain; lead to in client substrate ubiquitylation and degradation by the proteasome. CHIP targets misfolded chaperone substrates towards proteasomal degradation. CHIP mediates transfer of non-canonical short ubiquitin chains to HSPA8 that have no effect on HSPA8 degradation. CHIP plays a role in base-excision repair: catalyzes polyubiquitination by amplifying the HUWE1/ARF-BP1-dependent monoubiquitination and leading to POLB-degradation by the proteasome. It also may regulate the receptor stability and activity through proteasomal degradation.

Small Glutamine-Rich Tetratricopeptide Repeat-Containing Protein α (SGTA) is an ubiquitously expressed protein which belongs to the SGT Family. SGTA contains three TPR Protein-Protein Interaction Duplicates. SGTA is a co-chaperone that binds directly to HSC70 and HSP70 and regulates their ATPase activity. SGTA is capable of interacting with the major nonstructural protein of Parvovirus H-1 and 70-kDa heat shock cognate protein. It interacts with NS1 from Parvovirus H-1, with Vpu and Gag from HIV-1. It also interacts with SARS-CoV Accessory Protein 7a, DNAJC5 and DNAJC5B. However, its function is not known. Since this transcript is expressed ubiquitously in various tissues, SGTA may serve a housekeeping function.