NOPCHAP1 is a PAQosome cofactor that helps loading NOP58 on RUVBL1/2 during box C/D snoRNP biogenesis

Abstract

The PAQosome is a large complex composed of the HSP90/R2TP chaperone and a prefoldin-like module. It promotes the biogenesis of cellular machineries but it is unclear how it discriminates closely related client proteins. Among the main PAQosome clients are C/D snoRNPs and in particular their core protein NOP58. Using NOP58 mutants and proteomic experiments, we identify different assembly intermediates and show that C12ORF45, which we rename NOPCHAP1, acts as a bridge between NOP58 and PAQosome. NOPCHAP1 makes direct physical interactions with the CC-NOP domain of NOP58 and domain II of RUVBL1/2 AAA+ ATPases. Interestingly, NOPCHAP1 interaction with RUVBL1/2 is disrupted upon ATP binding. Moreover, while it robustly binds both yeast and human NOP58, it makes little interactions with NOP56 and PRPF31, two other closely related CC-NOP proteins. Expression of NOP58, but not NOP56 or PRPF31, is decreased in NOPCHAP1 KO cells. We propose that NOPCHAP1 is a client-loading PAQosome cofactor that selects NOP58 to promote box C/D snoRNP assembly.

The HSP90/R2TP assembly chaperone promotes cell proliferation in the intestinal epithelium

“…Misfolded HSP90 clients are usually degraded 38 , so we determined the expression levels of R2TP clients in VilCreER T2 ; Rpap3 flox/flox animals at day 6. R2TP was initially characterized as an assembly factor for the box C/D snoRNPs, and in particular it chaperones NOP58, one of the four core proteins in these particles 15 , 39 . Western blot analysis of crypt cell lysates showed a near twofold reduction of NOP58 levels in extracts from VilCreER T2 ; Rpap3 flox/flox animals, as compared to controls (Fig.…”

The genomics of phenotypically differentiated Asellusaquaticus cave, surface stream and lake ecotypes

“…However, only one was functionally annotated: NOP58 . This gene also fell into the confidence interval of a size‐related QTL (surface area) and is involved in ATPase binding and ribosome biogenesis in mice (Abel et al, 2021). The detection of our body pigmentation QTL is in accordance with Protas et al, (2011), who also found a main effect pigmentation QTL on LG2 using a cave × surface A .…”

“…However, only one was functionally annotated: NOP58. This gene also fell into the confidence interval of a size-related QTL (surface area) and is involved in ATPase binding and ribosome biogenesis in mice (Abel et al, 2021).…”

The Role of Hsp90-R2TP in Macromolecular Complex Assembly and Stabilization

“…When HEK293 cell lines expressing GFP-tagged proteins were treated with geldanamycin, NOP58 and 15.5K failed to accumulate, while a mild effect was seen for NOP56 [ 9 ]. NOP58 mutants, NOP58-K310A-A313R, and NOP58-A283P, which cannot assemble into mature snoRNPs, showed stronger interactions with Hsp90 than NOP58-WT [ 49 ]. NOP58-A283P also associated with the Hsp70-Hsp90 adaptor Hop [ 49 ].…”

“…NOP58 mutants, NOP58-K310A-A313R, and NOP58-A283P, which cannot assemble into mature snoRNPs, showed stronger interactions with Hsp90 than NOP58-WT [ 49 ]. NOP58-A283P also associated with the Hsp70-Hsp90 adaptor Hop [ 49 ]. Therefore, NOP58 is likely stabilized through the Hsp70-Hop-Hsp90 pathway during its maturation and assembly into snoRNPs.…”