Nutritional status modulates box C/D snoRNP biogenesis by regulated subcellular relocalization of the R2TP complex

Abstract

Background: Box C/D snoRNPs, which are typically composed of box C/D snoRNA and the four core protein components Nop1, Nop56, Nop58, and Snu13, play an essential role in the modification and processing of pre-ribosomal RNA. The highly conserved R2TP complex, comprising the proteins Rvb1, Rvb2, Tah1, and Pih1, has been shown to be required for box C/D snoRNP biogenesis and assembly; however, the molecular basis of R2TP chaperone-like activity is not yet known. Results: Here, we describe an unexpected finding in which the activity of the R2TP complex is required for Nop58 protein stability and is controlled by the dynamic subcellular redistribution of the complex in response to growth conditions and nutrient availability. In growing cells, the complex localizes to the nucleus and interacts with box C/D snoRNPs. This interaction is significantly reduced in poorly growing cells as R2TP predominantly relocalizes to the cytoplasm. The R2TP-snoRNP interaction is mainly mediated by Pih1. Conclusions:The R2TP complex exerts a novel regulation on box C/D snoRNP biogenesis that affects their assembly and consequently pre-rRNA maturation in response to different growth conditions.

R2TP/Prefoldin-like component RUVBL1/RUVBL2 directly interacts with ZNHIT2 to regulate assembly of U5 small nuclear ribonucleoprotein

“…In this regard, it has been noted that snoRNP complex composition is mostly unaffected by yeast R2TP deletion mutants but that disruption in assembly arises when cells are grown under stress condition10. More recently, R2TP localization was shown to be affected by mTOR inhibitor treatment and that snoRNP biogenesis was consequently regulated by nutrient availability55. This is not the first time that a role has been proposed for R2TP/Prefoldin-like as an effector of the mTOR pathway.…”

C/D‐box snoRNAs form methylating and non‐methylating ribonucleoprotein complexes: Old dogs show new tricks

“…Unloading of RuvBL1/2, leads to further rearrangement and generated the final snoRNP complex (Figure 1C). The components of this system are conserved from human to yeast, where it was shown that the R2TP components PIH1D1 and RPAP3 shuttle between cytosol and nucleus using the Crm1 and Kap121 export/import systems [15], which is regulated by the nutritional status of the cells via the mTOR pathway [15] (Figure 1D). …”

“…Loss of these SNORDs mark the progression of smoldering multiple myeloma, which cannot be explained through their predicted roles in rRNA methylation [54]. It is known that the localization and function of the R2TP complex that is necessary to form snoRNPs (Figure 1B, D) is regulated by the mTOR pathway [15] and likely altered in cancer [14, 55], which could affect snoRNP formation, but the molecular role of these SNORDs in cancer cannot be explained by their action on rRNA.…”

Structural Features of the Box C/D snoRNP Pre-assembly Process Are Conserved through Species

“…Whereas the binding of HSP90/Hsp82 to its co-chaperone RPAP3/Tah1p has been well studied (Back et al, 2013;Pal et al, 2014;Quinternet et al, 2015), the role played by HSP90/Hsp82 in snoRNP assembly remains unclear. However, the Pih1p component of the R2TP complex has been shown to be associated with assembly factor Rsa1p and core protein Nop58p (Boulon et al, 2008;Kakihara et al, 2014). Pih1p contains a C-terminal CS (Chord-Sgt1) domain that interacts with Tah1p via an intermolecular b sheet and forms secondary contacts with Hsp82 (Back et al, 2013;Quinternet et al, 2015).…”

“…The N-terminal part of PIH1D1/Pih1p folds into a phospho-binding domain that, in mammals, has been shown to be involved in direct binding with the casein kinase CK2-phosphorylated form of the co-chaperone Tel2 protein (Horejsi et al, 2014). As the C-terminal tail of core protein Nop58 contains the consensus motif for CK2 phosphorylation, it has been hypothesized that the association between Nop58p and Pih1p could partly rely on post-translational modifications (Kakihara et al, 2014;Quinternet et al, 2015). RUVBL1 and RUVBL2, the AAA + ATPases of the R2TP complex, are also affiliated with the box C/D snoRNP assembly process, since they are engaged in a protein-only complex involving NOP58, NUFIP1, ZNHIT6 (alias BCD1), and ZNHIT3 (alias TRIP3) (Bizarro et al, 2014).…”