A role for Lsmlp in response to ultraviolet-radiation damage in Saccharomyces cerevisiae

Ro60 and Y RNAs: structure, functions, and roles in autoimmunity

Ro60, also known as SS-A or TROVE2, is an evolutionarily conserved RNA-binding protein that is found in most animal cells, approximately 5% of sequenced prokaryotic genomes and some archaea. Ro60 is present in cells as both a free protein and as a component of a ribonucleoprotein complex, where its best-known partners are members of a class of noncoding RNAs called Y RNAs. Structural and biochemical analyses have revealed that Ro60 is a ring-shaped protein that binds Y RNAs on its outer surface. In addition to Y RNAs, Ro60 binds misfolded and aberrant noncoding RNAs in some animal cell nuclei. Although the fate of these defective Ro60-bound noncoding RNAs in animal cells is not well-defined, a bacterial Ro60 ortholog functions with 3' to 5' exoribonucleases to assist structured RNA degradation. Studies of Y RNAs have revealed that these RNAs regulate the subcellular localization of Ro60, tether Ro60 to effector proteins and regulate the access of other RNAs to its central cavity. As both mammalian cells and bacteria lacking Ro60 are sensitized to ultraviolet irradiation, Ro60 function may be important during exposure to some environmental stressors. Here we summarize the current knowledge regarding the functions of Ro60 and Y RNAs in animal cells and bacteria. Because the Ro60 RNP is a clinically important target of autoantibodies in patients with rheumatic diseases such as Sjogren's syndrome, systemic lupus erythematosus, and neonatal lupus, we also discuss potential roles for Ro60 RNPs in the initiation and pathogenesis of systemic autoimmune rheumatic disease.

A chemostat array enables the spatio-temporal analysis of the yeast proteome

Observing cellular responses to perturbations is central to generating and testing hypotheses in biology. We developed a massively parallel microchemostat array capable of growing and observing 1,152 yeast-GFP strains on the single-cell level with 20 min time resolution. We measured protein abundance and localization changes in 4,085 GFP-tagged strains in response to methyl methanesulfonate and analyzed 576 GFP strains in five additional conditions for a total of more than 10,000 unique experiments, providing a systematic view of the yeast proteome in flux. We observed that processing bodies formed rapidly and synchronously in response to UV irradiation, and in conjunction with 506 deletion-GFP strains, identified four gene disruptions leading to abnormal ribonucleotide-diphosphate reductase (Rnr4) localization. Our microchemostat platform enables the large-scale interrogation of proteomes in flux and permits the concurrent observation of protein abundance, localization, cell size, and growth parameters on the single-cell level for thousands of microbial cultures in one experiment.

Subcellular localization and interaction network of the mRNA decay activator Pat1 upon UV stress

To identify nucleo-cytoplasmic shuttle proteins that relocate to the nucleus upon UV stress, we selected 18 targets on the basis of their conservation amongst eukaryotes and their relatively poor functional description. Their relocation was assayed using quantitative nuclear relocation assay (QNR). We focused on Pat1, a component of the cytoplasmic foci called processing bodies (p-bodies), because it had the strongest response to the stress. We verified that Pat1 accumulates in the nucleus after GFP tagging and fluorescence microscopy. Using tandem affinity purification coupled to a mass spectrometry shotgun detection and quantitation approach, we explored the dynamics of Pat1 protein-protein interaction network after UV stress. We have shown that Pat1 co-purifies with Dhh1 specifically upon UV stress. We observed that the nuclear accumulation of Pat1 upon UV stress is abolished in a dhh1∆ strain. These data provide the first evidence that Dhh1 is required for Pat1 nuclear relocation after UV stress.