The human RNA helicase DHX37 is required for release of the U3 snoRNP from pre-ribosomal particles

Abstract

Ribosome synthesis is an essential cellular process, and perturbation of human ribosome production is linked to cancer and genetic diseases termed ribosomopathies. During their assembly, pre-ribosomal particles undergo numerous structural rearrangements, which establish the architecture present in mature complexes and serve as key checkpoints, ensuring the fidelity of ribosome biogenesis. RNA helicases are essential mediators of such remodelling events and here, we demonstrate that the DEAH-box RNA helicase DHX37 is required for maturation of the small ribosomal subunit in human cells. Our data reveal that the presence of DHX37 in early pre-ribosomal particles is monitored by a quality control pathway and that failure to recruit DHX37 leads to pre-rRNA degradation. Using an in vivo crosslinking approach, we show that DHX37 binds directly to the U3 small nucleolar RNA (snoRNA) and demonstrate that the catalytic activity of the helicase is required for dissociation of the U3 snoRNA from pre-ribosomal complexes. This is an important event during ribosome assembly as it enables formation of the central pseudoknot structure of the small ribosomal subunit. We identify UTP14A as a direct interaction partner of DHX37 and our data suggest that UTP14A can act as a cofactor that stimulates the activity of the helicase in the context of U3 snoRNA release.

Molecular mechanism of the RNA helicase DHX37 and its activation by UTP14A in ribosome biogenesis

“…9A,B; Supplemental Table S1), suggesting that UTP14A functions as an activator of DHX37 in part by increasing its RNA-dependent ATPase activity. This result stands in contrast to a previous observation that yeast Utp14 increases the RNA unwinding activity of Dhr1 in vitro without affecting ATPase activity (Zhu et al 2016) but is in good agreement with a recent study of human DHX37 (Choudhury et al 2018). Although DHX37 and Dhr1 have similar biological functions, it is possible that they use divergent molecular mechanisms.…”

“…Recent studies have suggested that UTP14A functions as a ribosome biogenesis factor in part by recruiting DHX37 to the maturing preribosomal particle (Choudhury et al 2018). Our biochemical experiments reveal that a conserved motif in UTP14A, distinct from the canonical DEAH-interacting motif found in G-patch proteins, is necessary and sufficient for interaction with DHX37.…”

“…This suggests that Utp14 regulates the recruitment and activity of Dhr1 during the transition from the SSU processome to the pre-40S particle, and thereby the timing of the maturation of the 40S subunit. Dhr1 and Utp14 have highly conserved mammalian orthologs, DHX37 and UTP14A, both of which have also been implicated in ribosome biogenesis (Choudhury et al 2018). However, the structural and mechanistic details of the RNA remodeling activity of Dhr1/DHX37 and its stimulation by Utp14/ UTP14A remain elusive at present.…”

Disorders of Sex Development—Novel Regulators, Impacts on Fertility, and Options for Fertility Preservation

“…Variants of the DEAH-box helicase 37 (DHX37) gene have recently been identified as an important cause of 46,XY GD, especially for embryonic testicular regression syndrome (ETRS). DHX37 is an RNA-helicase which has a role of DHX37 in ribosome biogenesis [125] and is expressed in the somatic cell lineage of the mouse and human (7-12 weeks of gestation) gonad early during testis determination and development [126]. Co-expression with Sox9 in a proportion of cells indicates the presence of DHX37 in Sertoli cells [126], whilst it is also expressed in Leydig cell cytoplasm and in germ cells at different stages of maturation (27 and 33 weeks of gestation) and, in adult human testes, the protein is mainly localized in spermatogonia [126,127].…”

Uncovering the assembly pathway of human ribosomes and its emerging links to disease

“…Although the roles of some RNA helicases are common to yeast and humans (e.g. yeast Dhr1 and human DHX37 both mediate release of the U3 snoRNA; Martin et al , ; Sardana et al , ; Choudhury et al , ), additional pre‐ribosomal functions have been described for several human RNA helicases. Examples include the requirement for DDX51 for release of the metazoan‐specific snoRNA U8 from pre‐LSU complexes (Srivastava et al , ), as well as the roles of DDX21 in coupling pre‐rRNA transcription and processing, and facilitating the access of late‐acting small nucleolar RNP (snoRNPs) to pre‐40S complexes (Calo et al , ; Sloan et al , ).…”