Project description:We performed a RNA immunoprecipitations experiments using gfp-specific antibodies to precipitate gfp-tagged La proteins from from gfp-La wild type and sumoylation deficient La mutant (K41/200R) cells and found that specific mRNAs are preferentially enriched gfp-La wild type RIPs when compared to sumoylation deficient La mutant (K41/200R) RIPs.
Project description:The exchange of mobile genomic islands (MGIs) between microorganisms is often mediated by phages. As a consequence, not only phage genes are transferred, but also genes that have no particular function in the phage's lysogenic cycle. If they provide benefits to the phage's host, such genes are referred to as ‘morons’. The present study was aimed at characterizing a set of Enterobacter cloacae, Klebsiella pneumoniae and Escherichia coli isolates with exceptional antibiotic resistance phenotypes from patients in a neonatal ward. Unexpectedly, these analyses unveiled the existence of a novel family of closely related MGIs in Enterobacteriaceae. The respective MGI from E. cloacae was named MIR17-GI. Importantly, our observations show that MIR17-GI-like MGIs harbor genes associated with high-level resistance to cephalosporins. Further, we show that MIR17-GI-like islands are associated with integrated P4-like prophages. This implicates phages in the spread of cephalosporin resistance amongst Enterobacteriaceae. The discovery of a novel family of MGIs spreading ‘cephalosporinase morons’ is of high clinical relevance, because high-level cephalosporin resistance has serious implications for the treatment of patients with Enterobacteriaceal infections.
Project description:In this study we investigated the steady-state growth of Methylotuvimicrobium alcaliphilum 20ZR in media containing calcium (Ca) or lanthanum (La, a REE element). RNA-seq profiling of Methylomicrobium alcaliphilum strain 20ZR in bioreactor on methane. Sample cultures, La-optimum, La-CH4 limited, Ca-optimum and Ca-CH4 limited, were collected and immediately transferred into tubes containing 5 ml of the stop solution (5% water-equilibrated phenol in ethanol). It was found, that cells supplemented with La show a higher growth rate compared to Ca-cultures; however, the efficiency of carbon conversion, estimated as biomass yield, is higher in cells grown with Ca. The study was financially supported by DOE under FOA DE-FOA-0001085 and by NSF-CBET award 1605031
Project description:The Lupus autoantigen (La) is a single-stranded RNA-binding protein that stabilizes RNA polymerase III (pol III) transcripts and supports RNA folding. In addition, La has been implicated in different steps of the mammalian small RNA pathway. Here, we have analyzed effects of La depletion on the Argonaute (Ago)-bound small RNAs in human cells. We find that in the absence of La, distinct tRNA fragments are loaded into Ago protein complexes and our data suggests that La prevents the production and loading of such tRNA fragments. However, one specific isoleucine tRNA escapes this regulation and produces both a functional tRNA as well as a microRNA (miRNA). We demonstrate that fully complementary 5' leader and 3' trailer of the pre-tRNA-Ile form a double-stranded RNA molecule that has low affinity to La. Instead, Exportin 5 (Xpo5) recognizes it as miRNA precursor and transports it into the cytoplasm for Dicer processing and Ago loading. Thus, La functions as gatekeeper to ensure correct tRNA generation and to protect the miRNA pathway from potentially functional tRNA fragments.
Project description:The Lupus autoantigen (La) is a single-stranded RNA-binding protein that stabilizes RNA polymerase III (pol III) transcripts and supports RNA folding. In addition, La has been implicated in different steps of the mammalian small RNA pathway. Here, we have analyzed effects of La depletion on the Argonaute (Ago)-bound small RNAs in human cells. We find that in the absence of La, distinct tRNA fragments are loaded into Ago protein complexes and our data suggests that La prevents the production and loading of such tRNA fragments. However, one specific isoleucine tRNA escapes this regulation and produces both a functional tRNA as well as a microRNA (miRNA). We demonstrate that fully complementary 5' leader and 3' trailer of the pre-tRNA-Ile form a double-stranded RNA molecule that has low affinity to La. Instead, Exportin 5 (Xpo5) recognizes it as miRNA precursor and transports it into the cytoplasm for Dicer processing and Ago loading. Thus, La functions as gatekeeper to ensure correct tRNA generation and to protect the miRNA pathway from potentially functional tRNA fragments.
Project description:La proteins bind the UUU-3’OH sequence found at the 3’-end of nascent RNA polymerase III transcripts, including pre-tRNAs, using a tandem arrangement of a winged-helix fold La motif (LaM) and an adjacent RNA recognition motif (RRM). La binding in diverse species results in protection of the 3’-end from exonucleases, stabilization of the pre-tRNA species and promotion of pre-tRNA folding until the UUU-3’OH containing trailer is endonucleolytically cleaved. Based on sequence conservation in the LaM, the Tetrahymena thermophila protein MLP1 (and related factors in other alveolates) has been hypothesized to function as a genuine La protein, despite the absence of the adjacent RRM found in La proteins of all prior investigated species. We show that MLP1 functions as a genuine La protein in that it binds and affects the processing of pre-tRNAs in T. thermophila and when expressed as a heterologous factor in fission yeast, however, unlike in other examined eukaryotes, depletion of MLP1 results in 3’-trailer stabilization. We also observed that 3’-trailers in T. thermophila are uniquely shortened relative to other examined eukaryotes, and that 5’-leaders in this species have evolved to disfavour pre-tRNA leader/trailer pairing. Our data suggest that the variant MLP1 architecture relative to other genuine La proteins is linked to an altered mechanism of tRNA processing in T. thermophila.