During their biogenesis, 40S ribosomal subunit precursors are exported from the nucleus to the cytoplasm, where final maturation occurs. In this study, we show that the protein kinase human Rio2 (hRio2) is part of a late 40S preribosomal particle in human cells. Using a novel 40S biogenesis and export assay, we analyzed the contribution of hRio2 to late 40S maturation. Although hRio2 is not absolutely required for pre-40S export, deletion of its binding site for the export receptor CRM1 decelerated the kinetics of this process. Moreover, in the absence of hRio2, final cytoplasmic 40S maturation is blocked because the recycling of several trans-acting factors and cytoplasmic 18S-E precursor ribosomal RNA (rRNA [pre-rRNA]) processing are defective. Intriguingly, the physical presence of hRio2 but not its kinase activity is necessary for the release of hEnp1 from cytoplasmic 40S precursors. In contrast, hRio2 kinase activity is essential for the recycling of hDim2, hLtv1, and hNob1 as well as for 18S-E pre-rRNA processing. Thus, hRio2 is involved in late 40S maturation at several distinct steps.
hRio1 is an atypical protein kinase of the conserved RIO family. Depletion of hRio1 affects the last step of 18S rRNA maturation and causes defects in recycling of trans-acting factors from pre-40S subunits in the cytoplasm. The kinase activity of hRio1 is essential for recycling of the endonuclease hNob1 and its binding partner hDim2 from pre-40S.
Biogenesis of 40S pre-ribosomal subunits requires many transacting factors, among them several protein kinases. In this study, we show that the human casein kinase 1 (CK1) isoforms d and e are required for cytoplasmic maturation steps of 40S subunit precursors. We show that both CK1d and CK1e isoforms are components of pre-40S subunits, on which they phosphorylate the ribosome biogenesis factors ENP1/BYSL and LTV1. Inhibition or codepletion of CK1d and CK1e results in failure to recycle a series of trans-acting factors including ENP1/BYSL, LTV1, RRP12, DIM2/ PNO1, RIO2 and NOB1 from pre-40S particles after nuclear export. Furthermore, co-depletion of CK1d and CK1e leads to defects in 18S-E pre-rRNA processing. Together, these data demonstrate that CK1d and CK1e play a decisive role in triggering late steps of pre-40S maturation that are required for acquisition of functionality of 40S ribosomal subunits in protein translation.
The demographic shift in the human population reflects an aging society-over 20% of Europeans are predicted to be 65 or over by the year 2025 (Riera & Dillin, 2015). Aging is the major risk factor for developing chronic diseases, such as cancer, Alzheimer's disease, and cardiovascular complications (Partridge et al., 2018).Unfortunately, humans spend on average one-fifth of their lifetime in poor health suffering from one or multiple age-related chronic diseases (Partridge et al., 2018). However, the onset of age-related pathologies is not fixed, and the rate of aging was shown to be malleable. The goal of biomedical research on aging or geroscience is to identify interventions that compress late-life morbidity to increase the period spent healthy and free from disease.
dThe interleukin enhancer binding factors ILF2 (NF45) and ILF3 (NF90/NF110) have been implicated in various cellular pathways, such as transcription, microRNA (miRNA) processing, DNA repair, and translation, in mammalian cells. Using tandem affinity purification, we identified human NF45 and NF90 as components of precursors to 60S (pre-60S) ribosomal subunits. NF45 and NF90 are enriched in nucleoli and cosediment with pre-60S ribosomal particles in density gradient analysis. We show that association of the NF45/NF90 heterodimer with pre-60S ribosomal particles requires the double-stranded RNA binding domains of NF90, while depletion of NF45 and NF90 by RNA interference leads to a defect in 60S biogenesis. Nucleoli of cells depleted of NF45 and NF90 have altered morphology and display a characteristic spherical shape. These effects are not due to impaired rRNA transcription or processing of the precursors to 28S rRNA. Consistent with a role of the NF45/NF90 heterodimer in nucleolar steps of 60S subunit biogenesis, downregulation of NF45 and NF90 leads to a p53 response, accompanied by induction of the cyclin-dependent kinase inhibitor p21/CIP1, which can be counteracted by depletion of RPL11. Together, these data indicate that NF45 and NF90 are novel higher-eukaryote-specific factors required for the maturation of 60S ribosomal subunits. T he nuclear factors NF45 and NF90 (NFAR-1, DRBP76, MPP4, and TCP80) were originally discovered as a heterodimeric complex binding to the interleukin-2 (IL-2) promoter (1, 2) and are also referred to as interleukin enhancer-binding factors 2 (ILF2) and 3 (ILF3), respectively (3). While NF90 is vertebrate specific, NF45 is found throughout metazoans.In mammals, the NF45/NF90 complex is widely expressed across tissues (4). Over recent years, NF45/NF90 has been implicated in a great variety of biological processes. Apart from regulation of transcription (5-7), the heterodimer has also been linked to numerous other pathways, such as DNA damage response (8, 9), mRNA metabolism (10, 11), microRNA (miRNA) biogenesis (12), and viral infection (13-17). NF90 knockout mice display severe defects in skeletal muscle formation leading to respiratory failure soon after birth (18), indicating an essential role of NF90 function in vertebrate development.Both NF45 and NF90 possess an N-terminal "domain associated with zinc fingers" (DZF) that is found only in metazoan proteins. Recent structural analysis revealed that the DZF domains of NF45 and NF90 resemble template-free nucleotidyltransferases and mediate their heterodimerization through a structurally conserved interface (19). In addition to the DZF domain, NF90 possesses two double-stranded RNA binding domains (dsRBDs) in the C-terminal region (2, 20) that confer binding to highly structured RNAs (21-23).NF90 is expressed from at least five alternatively spliced mRNAs that all encode the DZF and dsRBDs. Some of the splice variants generate C-terminally extended protein isoforms referred to as NF110 (NFAR-2) (24, 25), which also interact with ...
Edited by Felix WielandKeywords: BCCIP Ribosome biogenesis Eukaryotic initiation factor 6 (eIF6) Ribosomal protein RPL23/uL14 a b s t r a c t BRCA2 and CDKN1A(p21,CIP1)-interacting protein (BCCIP) is an evolutionary conserved protein implicated in maintenance of genome stability and cell cycle progression. Two isoforms of BCCIP with distinct C-terminal domains exist in humans. We show that mammalian BCCIPb, but not BCCIPa, forms a ternary complex with the ribosomal protein RPL23/uL14 and the pre-60S transacting factor eIF6. Complex formation is dependent on an intact C-terminal domain of BCCIPb. Depletion of BCCIPb reduces the pool of free RPL23, and decreases eIF6 levels in nucleoli. Overexpression of BCCIPb leads to nucleoplasmic accumulation of extra-ribosomal RPL23 and stabilizes overexpressed RPL23, suggesting that BCCIPb functions as nuclear chaperone for RPL23.
The identification and validation of drugs that promote health during aging (‘geroprotectors’) is key to the retardation or prevention of chronic age-related diseases. Here we found that most of the established pro-longevity compounds shown to extend lifespan in model organisms also alter extracellular matrix gene expression (i.e., matrisome) in human cell lines. To harness this novel observation, we used age-stratified human transcriptomes to define the age-related matreotype, which represents the matrisome gene expression pattern associated with age. Using a ‘youthful’ matreotype, we screened in silico for geroprotective drug candidates. To validate drug candidates, we developed a novel tool using prolonged collagen expression as a non-invasive and in-vivo surrogate marker for C. elegans longevity. With this reporter, we were able to eliminate false positive drug candidates and determine the appropriate dose for extending the lifespan of C. elegans. We improved drug uptake for one of our predicted compounds, genistein, and reconciled previous contradictory reports of its effects on longevity. We identified and validated new compounds, tretinoin, chondroitin sulfate, and hyaluronic acid, for their ability to restore age-related decline of collagen homeostasis and increase lifespan. Thus, our innovative drug screening approach - employing extracellular matrix homeostasis - facilitates the discovery of pharmacological interventions promoting healthy aging.HighlightsMany geroprotective drugs alter extracellular matrix gene expressionDefined young and old human matreotype signatures can identify novel potential geroprotective compoundsProlonged collagen homeostasis as a surrogate marker for longevity
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.