The specialized cytosolic J-protein, Jjj1, functions in 60S ribosomal subunit biogenesis

Department of Biochemistry, 433 Babcock Drive, University of Wisconsin, Madison, WI 53706, USA.
Proceedings of the National Academy of Sciences (Impact Factor: 9.67). 02/2007; 104(5):1558-63. DOI: 10.1073/pnas.0610704104
Source: PubMed


J-proteins and Hsp70 chaperones function together in diverse cellular processes. We identified a cytosolic J-protein, Jjj1, of Saccharomyces cerevisiae that is associated with 60S ribosomal particles. Unlike Zuo1, a 60S subunit-associated J-protein that is a component of the chaperone machinery that binds nascent polypeptide chains upon their exit from the ribosome, Jjj1 plays a role in ribosome biogenesis. Cells lacking Jjj1 have phenotypes very similar to those lacking Rei1, a ribosome biogenesis factor associated with pre-60S ribosomal particles in the cytosol. Jjj1 stimulated the ATPase activity of the general cytosolic Hsp70 Ssa, but not Ssb, Zuo1's ribosome-associated Hsp70 partner. Overexpression of Jjj1, which is normally approximately 40-fold less abundant than Zuo1, can partially rescue the phenotypes of cells lacking Zuo1 as well as cells lacking Ssb. Together, these results are consistent with the idea that Jjj1 normally functions with Ssa in a late, cytosolic step of the biogenesis of 60S ribosomal subunits. In addition, because of its ability to bind 60S subunits, we hypothesize that Jjj1, when overexpressed, is able to partially substitute for the Zuo1:Ssb chaperone machinery by recruiting Ssa to the ribosome, facilitating its interaction with nascent polypeptide chains.

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Available from: Arlen Johnson, Jan 13, 2014
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    • "Although the role of TORC1 in phosphorylation of ribosomal protein S6 (RPS6) via S6-kinase (S6K) is known (Feldman et al., 2009; Richardson et al., 2004; Urban et al., 2007), the involvement of TORC2 was not appreciated until recently (Zinzalla et al., 2011). Our data support a role of TORC2 in ribosome biogenesis, since two genes (TMA23 and JJJ1) involved in ribosome biogenesis (Fleischer et al., 2006; Meyer et al., 2007) and a ribosomal protein (RPL37A) show strong positive interactions with TORC2 while simultaneously showing strong negative interactions with TORC1 (Figure 2G). This indicates that these genes are in a pathway with TORC2 and provides additional evidence that ribosomal biogenesis plays a role in regulating TORC2 (Zinzalla et al., 2011). "
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    ABSTRACT: Current approaches for identifying synergistic targets use cell culture models to see if the combined effect of clinically available drugs is better than predicted by their individual efficacy. New techniques are needed to systematically and rationally identify targets and pathways that may be synergistic targets. Here, we created a tool to screen and identify molecular targets that may synergize with new inhibitors of target of rapamycin (TOR), a conserved protein that is a major integrator of cell proliferation signals in the nutrient-signaling pathway. Although clinical results from TOR complex 1 (TORC1)-specific inhibition using rapamycin analogs have been disappointing, trials using inhibitors that also target TORC2 have been promising. To understand this increased therapeutic efficacy and to discover secondary targets for combination therapy, we engineered Tor2 in S. cerevisiae to accept an orthogonal inhibitor. We used this tool to create a chemical epistasis miniarray profile (ChE-MAP) by measuring interactions between the chemically inhibited Tor2 kinase and a diverse library of deletion mutants. The ChE-MAP identified known TOR components and distinguished between TORC1- and TORC2-dependent functions. The results showed a TORC2-specific interaction with the pentose phosphate pathway, a previously unappreciated TORC2 function that suggests a role for the complex in balancing the high energy demand required for ribosome biogenesis.
    Cell Reports 12/2013; 5(6). DOI:10.1016/j.celrep.2013.11.040 · 8.36 Impact Factor
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    • "In more detail, Rei1p interacts with the cytosolic shuttling factors Associated with ribosomal export complex1 (Arx1p), ARX1 little brother1 (Alb1p), Ribosomal-like protein24 (Rlp24p), ribosomal protein of the large sub- unit24A (Rpl24Ap), Rpl24Bp, Type III j-protein1 (Jjj1p), and translation initiation factor6 (Tif6p) (Hung and Johnson, 2006; Lebreton et al., 2006; Meyer et al., 2007). Rei1p is thought to be recruited to the cytosolic pre-60S subunit by Rlp24p. "
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    ABSTRACT: The evolutionarily conserved proteins REIL1 and REIL2 (for REI1-LIKE) have four conserved zinc finger domains and are A. thaliana homologs of the cytosolic 60S ribosomal maturation factor Rei1p from yeast and its paralog Reh1p. The yeast and A. thaliana paralogs result from independent gene duplications. The A. thaliana REIL paralogs are required specifically in the cold (10°C) but not for growth at optimal temperature (20°C). A reil1-1 reil2-1 double mutant is arrested at 10°C prior to the emergence of the first rosette leaf. Two allelic reil2 mutants, reil2-1 and reil2-2, form small spoon-shaped leafs at 10°C. This phenomenon reverts after emergence of the inflorescence in the cold or upon shift to 20°C. Except for a slightly delayed germination, a reil1-1 mutant shows no further growth phenotype under the currently investigated conditions. A comparative analysis demonstrates conserved co-expression of orthologous genes from yeast and A. thaliana that are co-regulated with yeast rei1 or with A. thaliana REIL2, respectively. The conserved correlations point to a role of A. thaliana REIL proteins in the maturation of the eukaryotic ribosomal 60S subunit. We support this conclusion by heterologous complementation of the cold induced growth defect of the yeast Δrei1 deletion.
    Plant physiology 09/2013; 163(4). DOI:10.1104/pp.113.223925 · 6.84 Impact Factor
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    • "Therefore, DnaJ may be an important virulence factor which confers fitness for pneumococci to adapt host stress by interacting with the ribosomal proteins. This result is supported by the observation on other bacteria, such as E. coli and Saccharomyces cerevisiae [19, 24, 39]. Thus, DnaJ-mediated host adaptation may be a common phenomenon among bacteria. "
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    ABSTRACT: Streptococcus pneumoniae DnaJ is recognized as a virulence factor whose role in pneumococcal virulence remains unclear. Here, we attempted to reveal the contribution of DnaJ in pneumococcal virulence from the identification of its interacting proteins using co-immunoprecipitation method. dnaJ was cloned into plasmid pAE03 generating pAE03-dnaJ-gfp which was used to transform S. pneumoniae D39 strain. Then anti-GFP coated beads were used to capture GFP-coupled proteins from the bacterial lysate. The resulting protein mixtures were subjected to SDS-PAGE and those differential bands were determined by matrix-assisted laser desorption/ionization time of flight mass spectrometry. We finally obtained nine proteins such as DnaK, Gap, Eno, SpxB using this method. Furthermore, to confirm the interaction between DnaJ and these candidates, bacterial two-hybrid system was employed to reveal, for example, the interaction between DnaJ and DnaK, Eno, SpxB. Further protein expression experiments suggested that DnaJ prevented denaturation of Eno and SpxB at high temperature. These results help to understand the role of DnaJ in the pathogenesis of S. pneumoniae.
    Current Microbiology 08/2013; 67(6). DOI:10.1007/s00284-013-0424-4 · 1.42 Impact Factor
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