Project description:Because plants are immobile, they have developed intricate mechanisms to sense and absorb nutrients, adjusting their growth and development accordingly. Sulfur is an essential macroelement, but our understanding of its metabolism and homeostasis is limited. LSU (RESPONSE TO LOW SULFUR) proteins are plant-specific proteins with unknown molecular functions and were first identified during transcriptomic studies on sulfur deficiency in Arabidopsis. These proteins are crucial hubs that integrate environmental signals and are involved in the response to various stressors. Herein, we report the direct involvement of LSU proteins in primary sulfur metabolism for the first time. Our findings revealed that the quadruple lsu mutant, q-lsu-KO, which was grown under nonlimiting sulfate conditions, exhibited a molecular response resembling that of sulfur-deficient wild-type plants. This led us to explore the interactions of LSU proteins with sulfate reduction pathway enzymes. We found that all LSU proteins interact with ATPS1 and ATPS3 isoforms of ATP sulfurylase, all three isoforms of adenosine 5´phosphosulfate reductase (APR), and sulfite reductase (SiR). Additionally, in vitro assays revealed that LSU1 enhances the enzymatic activity of SiR. These results highlight the supportive role of LSU proteins in the sulfate reduction pathway.
Project description:Yeast large ribosomal subunit (LSU) precursors are subject to substantial changes in protein composition during their maturation due to coordinated transient interactions with a large number of ribosome biogenesis factors and due to the assembly of ribosomal proteins. These compositional changes go along with stepwise processing of LSU rRNA precursors and with specific rRNA folding events, as revealed by recent cryo-electron microscopy analyses of late nuclear and cytoplasmic LSU precursors. Here we aimed to analyze changes in the spatial rRNA surrounding of selected ribosomal proteins during yeast LSU maturation. For this we combined a recently developed tethered tertiary structure probing approach with both targeted and high-throughput readout strategies. Several structural features of late LSU precursors were faithfully detected by this procedure. In addition, the obtained data let us suggest that early rRNA precursor processing events are accompanied by a global transition from a flexible to a spatially restricted rRNA conformation. For intermediate LSU precursors, a number of structural hallmarks could be addressed which include the fold of the internal transcribed spacer between 5.8S rRNA and 25S rRNA, the orientation of the central protuberance and the spatial organization of the interface between LSU rRNA domains I and III.
Project description:The members of plant-specific LSU (RESPONSE TO LOW SULFUR) family were first identified as strongly induced during sulfur starvation. Molecular function of these protein remains unknown, however they were identified as important stress-related hubs by several research groups. In Arabidopsis thaliana there are four members of LSU family. These proteins are involved in multiple protein-protein interactions and literature data suggest that they can integrate abiotic and biotic stress responses. LSU proteins are small and have the coiled-coil structure. Additionally to binding with other proteins they can form homo- and heterodimers and possibly also multimers. In this work we investigated interactions between different monomers of LSU1-4 using Y2H and BiFC methods. The differences in strength of various homo- and heterodimers formation were observed. The constructed by us structural models of the LSU1-4 homo- and heterodimers were in agreement with the experimental observations concerning differences in strength of dimers formation and might help understanding interaction of LSU with other partners. Since previously the partners of LSU were identified using the Y2H approach we decided to obtain the lists of LSU interactors in plants using the TAP-tagged LSU1-4. Interaction of LSUs with a few selected proteins from the lists was verified by Y2H and BiFC.
Project description:Background: Sm proteins are multimeric RNA-binding factors, found in all three domains of life. Eukaryotic Sm proteins, together with their associated RNAs, form small ribonucleoprotein (RNP) complexes important in multiple aspects of gene regulation. Comprehensive knowledge of the RNA components of Sm RNPs is critical for understanding their functions. Results: We developed a multi-targeting RNA-immunoprecipitation sequencing (RIP-seq) strategy to reliably identify Sm-associated RNAs from Drosophila ovaries and cultured human cells. Using this method, we discovered three major categories of Sm-associated transcripts: small nuclear (sn)RNAs, small Cajal body (sca)RNAs and mRNAs. Additional RIP-PCR analysis showed both ubiquitous and tissue-specific interactions. We provide evidence that the mRNA-Sm interactions are mediated by snRNPs, and that one of the mechanisms of interaction is via base pairing. Moreover, the Sm-associated mRNAs are mature, indicating a splicing-independent function for Sm RNPs. Conclusions: This study represents the first comprehensive analysis of eukaryotic Sm-containing RNPs, and provides a basis for additional functional analyses of Sm proteins and their associated snRNPs outside of the context of pre-mRNA splicing. Our findings expand the repertoire of eukaryotic Sm-containing RNPs and suggest new functions for snRNPs in mRNA metabolism.