The Hsp90 Cochaperones Cpr6, Cpr7, and Cns1 Interact with the Intact Ribosome

Abstract

The abundant molecular chaperone Hsp90 is essential for the folding and stabilization of hundreds of distinct client proteins. Hsp90 is assisted by multiple cochaperones that modulate Hsp90's ATPase activity and/or promote client interaction, but the in vivo functions of many of these cochaperones are largely unknown. We found that Cpr6, Cpr7, and Cns1 interact with the intact ribosome and that Saccharomyces cerevisiae lacking CPR7 or containing mutations in CNS1 exhibited sensitivity to the translation inhibitor hygromycin. Cpr6 contains a peptidyl-prolyl isomerase (PPIase) domain and a tetratricopeptide repeat (TPR) domain flanked by charged regions. Truncation or alteration of basic residues near the carboxy terminus of Cpr6 disrupted ribosome interaction. Cns1 contains an amino-terminal TPR domain and a poorly characterized carboxy-terminal domain. The isolated carboxy-terminal domain was able to interact with the ribosome. Although loss of CPR6 does not cause noticeable growth defects, overexpression of CPR6 results in enhanced growth defects in cells expressing the temperature-sensitive cns1-G90D mutation (the G-to-D change at position 90 encoded by cns1). Cpr6 mutants that exhibit reduced ribosome interaction failed to cause growth defects, indicating that ribosome interaction is required for in vivo functions of Cpr6. Together, these results represent a novel link between the Hsp90 molecular-chaperone machine and protein synthesis.

The Co-chaperone Cns1 and the Recruiter Protein Hgh1 Link Hsp90 to Translation Elongation via Chaperoning Elongation Factor 2

“…Notably, the first segment with helical propensity revealed by NMR coincides with the region that conveys the essential function of Cns1 identified in our viability assay. Several previous studies reported a functional overlap between Cns1 and Cpr7 in vivo (Marsh et al, 1998;Tenge et al, 2015;Tesic et al, 2003;Zuehlke and Johnson, 2012), but the nature of this genetic interaction was not clear. Moreover, both proteins were reported to weakly interact with the 80S ribosome (Albanè se et al, 2006;Tenge et al, 2015).…”

“…The cns1 and cpr7 mutant strains are known to be hypersensitive to the translation inhibitor hygromycin B (Albanè se et al., 2006;Tenge et al, 2015). Cns1 overexpression reverts this effect in the cpr7D strain ( Figure 4A).…”

“…In vitro studies showed that Cns1 binds to both Hsp90 and Hsp70 (Hainzl et al, 2004). Furthermore, Cns1 and Cpr7 interact weakly with the 80S ribosome, and cns1 and cpr7D mutants are sensitive to the translation inhibitor hygromycin B (Albanè se et al, 2006;Tenge et al, 2015).…”

Peptidyl‐Prolyl Isomerase Cpr7p of Yeast Prevents Protein Aggregation Upon Freezing

“…38 Although normal growth and full Hsp90 activity require Cpr7p, they do not require Cpr7p PPIase activity. 44 Intriguingly, yeasts lacking any components of the ribosome-associated complex (Ssb, Ssz1, and Zuo1) exhibit cold-sensitive growth. 39 The PPIase domain is suggested to mediate protein-protein interactions; thus, it may play a chaperoning role.…”

HSP90AB1: Helping the good and the bad

“…In addition, Cpr7 deletion resulted in a significant impairment of cell division (Duina et al 1996a). Both Cpr6 and Cpr7 interact with the ribosome and may be involved in the regulation of protein synthesis (Tenge et al 2015). …”