Rat RL23a Ribosomal Protein Efficiently Competes with itsSaccharomyces cerevisiaeL25 Homologue for Assembly Into 60 S Subunits

Jeeninga, Rienk E.; Venema, Jaap; Raué, Hendrik A.

doi:10.1006/jmbi.1996.0605

Cited by 12 publications

(7 citation statements)

References 36 publications

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“…2C). Similar to rpL12, rpL23a is a 60S subunit component that binds to the 28S rRNA (16,37). The influence of importin 11 on the nuclear localization of rpL12 was further confirmed in cells overexpressing importin 11(78-975).…”

Section: Vol 22 2002 Importin 11 Mediates Rpl12 Import 1267mentioning

confidence: 84%

Ribosomal Protein L12 Uses a Distinct Nuclear Import Pathway Mediated by Importin 11

Plafker

Macara

2002

Molecular and Cellular Biology

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Ribosome biogenesis requires the nuclear translocation of ribosomal proteins from their site of synthesis in the cytoplasm to the nucleus. Analyses of the import mechanisms have revealed that most ribosomal proteins can be delivered to the nucleus by multiple transport receptors (karyopherins or importins). We now provide evidence that ribosomal protein L12 (rpL12) is distinguished from the bulk of ribosomal proteins because it accesses the importin 11 pathway as a major route into the nucleus. rpL12 specifically and directly interacted with importin 11 in vitro and in vivo. Both rpL12 binding to and import by importin 11 were inhibited by another importin 11 substrate, UbcM2, indicating that these two cargoes may bind overlapping sites on the transport receptor. In contrast, the import of rpL23a, a ribosomal protein that uses the general ribosomal protein import system, was not competed by UbcM2, and in an in vitro binding assay, importin 11 did not bind to the nuclear localization signal of rpL23a. Furthermore, in a transient transfection assay, the nuclear accumulation of rpL12 was increased by coexpressed importin 11, but not by other importins. These data are consistent with importin 11 being a mediator of rpL12 nuclear import. Taken together, these results indicate that rpL12 uses a distinct nuclear import pathway that may contribute to a mechanism for regulating ribosome synthesis and/or maturation.Assembly of the 40S and 60S subunits of the eukaryotic ribosome takes place within the nucleolar compartment of the nucleus. As a result, the ϳ75 ribosomal proteins necessary for ribosomal assembly and maturation must be imported into the nucleus and targeted to the nucleolus following their synthesis in the cytoplasm. Although the sizes of these proteins are well below the diffusion limit of the nuclear pore, ribosomal protein import requires energy and soluble nuclear transport factors (15, 32) that include a class of import receptors, often called karyopherins or importins. It has been reasoned (32) that such rapid, active transport is necessary because of the short cytoplasmic half-lives (2 to 3 min) of many ribosomal proteins (38,39).Importins recognize specific nuclear localization signals (NLSs) encoded in the sequences of their cargo proteins. The importins also interact with nucleoporins, which are components of the nuclear pore complex. This interaction permits a facilitated diffusive translocation of the importin-cargo complex through the pores. Within the nucleus, the importins bind to Ran:GTP, which triggers cargo release. The importin-Ran: GTP complex then recycles back to the cytoplasm, where the GTP on Ran is hydrolyzed, and Ran:GDP dissociates from the importins (all reviewed in references 5, 10,

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Section: Vol 22 2002 Importin 11 Mediates Rpl12 Import 1267mentioning

confidence: 84%

Ribosomal Protein L12 Uses a Distinct Nuclear Import Pathway Mediated by Importin 11

Plafker

Macara

2002

Molecular and Cellular Biology

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“…To date there are only a few reports that a yeast ribosomal protein can be replaced with a mammalian (or insect) homolog. Yeast rpL25 can be replaced by rat and Drosophila melanogaster rpL23A (Jeeninga et al 1996;Ross et al 2007) and mouse ribosomal protein rpL279 can substitute for the yeast rpL29 (Fleming et al 1989). These replacements all involved the large (60S) ribosomal subunit.…”

Section: Discussionmentioning

confidence: 99%

Roles of the negatively charged N-terminal extension of Saccharomyces cerevisiae ribosomal protein S5 revealed by characterization of a yeast strain containing human ribosomal protein S5

Galkin

Bentley

Gupta

et al. 2007

RNA

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Ribosomal protein (rp) S5 belongs to a family of ribosomal proteins that includes bacterial rpS7. rpS5 forms part of the exit (E) site on the 40S ribosomal subunit and is essential for yeast viability. Human rpS5 is 67% identical and 79% similar to Saccharomyces cerevisiae rpS5 but lacks a negatively charged (pI ;3.27) 21 amino acid long N-terminal extension that is present in fungi. Here we report that replacement of yeast rpS5 with its human homolog yielded a viable yeast strain with a 20%-25% decrease in growth rate. This replacement also resulted in a moderate increase in the heavy polyribosomal components in the mutant strain, suggesting either translation elongation or termination defects, and in a reduction in the polyribosomal association of the elongation factors eEF3 and eEF1A. In addition, the mutant strain was characterized by moderate increases in +1 and À1 programmed frameshifting and hyperaccurate recognition of the UAA stop codon. The activities of the cricket paralysis virus (CrPV) IRES and two mammalian cellular IRESs (CAT-1 and SNAT-2) were also increased in the mutant strain. Consistently, the rpS5 replacement led to enhanced direct interaction between the CrPV IRES and the mutant yeast ribosomes. Taken together, these data indicate that rpS5 plays an important role in maintaining the accuracy of translation in eukaryotes and suggest that the negatively charged N-terminal extension of yeast rpS5 might affect the ribosomal recruitment of specific mRNAs.

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“…C-terminal fusions were investigated because it has previously been shown that attachment of a small (approximately 2 kD) FLAG-His 6 tag to the C terminus of RPL23aA did not disrupt the ability of the fusion protein to incorporate into ribosomes and form polysomes (Zanetti et al, 2005). RPL23a orthologs are known to be involved in LSU biogenesis within the nucleolus (Jeeninga et al, 1996;van Beekvelt et al, 2001), and hence we hypothesized that Arabidopsis RPL23a would accumulate to the greatest extent in the nucleolus. To enable definitive identification of nucleolar accumulation, we used a nucleolar marker, Arabidopsis FIBRILLARIN2 (FIB2), with a C-terminal enhanced GFP (EGFP) tag (Barneche et al, 2000).…”

Section: C-terminally Tagged Rpl23a Isoforms Localize To the Nucleolusmentioning

confidence: 99%

Arabidopsis Ribosomal Proteins RPL23aA and RPL23aB Are Differentially Targeted to the Nucleolus and Are Disparately Required for Normal Development

2008

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Protein synthesis is catalyzed by the ribosome, a two-subunit enzyme comprised of four ribosomal RNAs and, in Arabidopsis (Arabidopsis thaliana), 81 ribosomal proteins (r-proteins). Plant r-protein genes exist as families of multiple expressed members, yet only one r-protein from each family is incorporated into any given ribosome, suggesting that many r-protein genes may be functionally redundant or development/tissue/stress specific. Here, we characterized the localization and gene-silencing phenotypes of a large subunit r-protein family, RPL23a, containing two expressed genes (RPL23aA and RPL23aB). Live cell imaging of RPL23aA and RPL23aB in tobacco with a C-terminal fluorescent-protein tag demonstrated that both isoforms accumulated in the nucleolus; however, only RPL23aA was targeted to the nucleolus with an N-terminal fluorescent protein tag, suggesting divergence in targeting efficiency of localization signals. Independent knockdowns of endogenous RPL23aA and RPL23aB transcript levels using RNA interference determined that an RPL23aB knockdown did not alter plant growth or development. Conversely, a knockdown of RPL23aA produced a pleiotropic phenotype characterized by growth retardation, irregular leaf and root morphology, abnormal phyllotaxy and vasculature, and loss of apical dominance. Comparison to other mutants suggests that the phenotype results from reduced ribosome biogenesis, and we postulate a link between biogenesis, microRNA-target degradation, and maintenance of auxin homeostasis. An additional RNA interference construct that coordinately silenced both RPL23aA and RPL23aB demonstrated that this family is essential for viability.

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Rat RL23a Ribosomal Protein Efficiently Competes with itsSaccharomyces cerevisiaeL25 Homologue for Assembly Into 60 S Subunits

Cited by 12 publications

References 36 publications

Ribosomal Protein L12 Uses a Distinct Nuclear Import Pathway Mediated by Importin 11

Ribosomal Protein L12 Uses a Distinct Nuclear Import Pathway Mediated by Importin 11

Roles of the negatively charged N-terminal extension of Saccharomyces cerevisiae ribosomal protein S5 revealed by characterization of a yeast strain containing human ribosomal protein S5

Arabidopsis Ribosomal Proteins RPL23aA and RPL23aB Are Differentially Targeted to the Nucleolus and Are Disparately Required for Normal Development

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