Arabidopsis ubiquitin ligase PUB41 positively regulates ABA-mediated seed dormancy and drought response.

Unlabelled: Seed germination is a tightly regulated, non-reversible developmental process, and it is crucial to prevent premature germination under conditions that may not allow the plant's life cycle to be completed. The plant hormone ABA is the key regulator of seed dormancy and inhibition of germination. ABA is also involved in the plant response to drought.

The activity of the stress modulated Arabidopsis ubiquitin ligases PUB46 and PUB48 is partially redundant.

The Arabidopsis ubiquitin ligases PUB46, PUB47 and PUB48 are encoded by paralogus genes. Single gene and mutants display increased drought sensitivity compared to wild type (WT) suggesting that each has specific biological activity. The high sequence homology between PUB46 and PUB48 activity suggested that they may also share some aspects of their activity.

Overexpression of Arabidopsis ubiquitin ligase AtPUB46 enhances tolerance to drought and oxidative stress.

The U-Box E3 ubiquitin ligase, AtPUB46, functions in the drought response: T-DNA insertion mutants of this single paralogous gene are hypersensitive to water- and oxidative stress (Adler et al. BMC Plant Biology 17:8, 2017). Here we analyze the phenotype of AtPUB46 overexpressing (OE) plants.

The Arabidopsis paralogs, PUB46 and PUB48, encoding U-box E3 ubiquitin ligases, are essential for plant response to drought stress.

Background: Plants respond to abiotic stress on physiological, biochemical and molecular levels. This includes a global change in their cellular proteome achieved by changes in the pattern of their protein synthesis and degradation. The ubiquitin-proteasome system (UPS) is a key player in protein degradation in eukaryotes.

Aggregation of human S100A8 and S100A9 amyloidogenic proteins perturbs proteostasis in a yeast model.

Amyloid aggregates of the calcium-binding EF-hand proteins, S100A8 and S100A9, have been found in the corpora amylacea of patients with prostate cancer and may play a role in carcinogenesis. Here we present a novel model system using the yeast Saccharomyces cerevisiae to study human S100A8 and S100A9 aggregation and toxicity. We found that S100A8, S100A9 and S100A8/9 cotransfomants form SDS-resistant non-toxic aggregates in yeast cells.

Transfer of Ho endonuclease and Ufo1 to the proteasome by the UbL-UbA shuttle protein, Ddi1, analysed by complex formation in vitro.

The F-box protein, Ufo1, recruits Ho endonuclease to the SCF(Ufo1) complex for ubiquitylation. Both ubiquitylated Ho and Ufo1 are transferred by the UbL-UbA protein, Ddi1, to the 19S Regulatory Particle (RP) of the proteasome for degradation. The Ddi1-UbL domain binds Rpn1 of the 19S RP, the Ddi1-UbA domain binds ubiquitin chains on the degradation substrate.

S100A8/A9 amyloidosis in the ageing prostate: relating ex vivo and in vitro studies.

The family of S100 proteins encompasses more than 20 members characterized by remarkable conformational and functional diversity. S100 proteins act as central regulators of various cellular processes, including cell survival, proliferation, differentiation, and motility. Many S100 proteins are implicated in various types of cancer as well as neurodegenerative, inflammatory, and autoimmune diseases.

Cloning, mutagenesis, and characterization of the microalga Parietochloris incisa acetohydroxyacid synthase, and its possible use as an endogenous selection marker.

Parietochloris incisa is an oleaginous fresh water green microalga that accumulates an unusually high content of the valuable long-chain polyunsaturated fatty acid (LC-PUFA) arachidonic acid within triacylglycerols in cytoplasmic lipid bodies. Here, we describe cloning and mutagenesis of the P. incisa acetohydroxyacid synthase (PiAHAS) gene for use as an herbicide resistance selection marker for transformation.

Sequestration of highly expressed mRNAs in cytoplasmic granules, P-bodies, and stress granules enhances cell viability.

Transcriptome analyses indicate that a core 10%-15% of the yeast genome is modulated by a variety of different stresses. However, not all the induced genes undergo translation, and null mutants of many induced genes do not show elevated sensitivity to the particular stress. Elucidation of the RNA lifecycle reveals accumulation of non-translating mRNAs in cytoplasmic granules, P-bodies, and stress granules for future regulation.

UV and arsenate toxicity: a specific and sensitive yeast bioluminescence assay.

We describe a Saccharomyces cerevisiae bioluminescence assay for UV and arsenate in which bacterial luciferase genes are regulated by the promoter of the yeast gene, UFO1. UFO1 encodes the F-box subunit of the Skp1–Cdc53–F-box protein ubiquitin ligase complex and is induced by DNA damage and by arsenate. We engineered the UFO1 promoter into an existing yeast bioreporter that employs human genes for detection of steroid hormone-disrupting compounds in water bodies.

Tubulin chaperone E binds microtubules and proteasomes and protects against misfolded protein stress.

Mutation of tubulin chaperone E (TBCE) underlies hypoparathyroidism, retardation, and dysmorphism (HRD) syndrome with defective microtubule (MT) cytoskeleton. TBCE/yeast Pac2 comprises CAP-Gly, LRR (leucine-rich region), and UbL (ubiquitin-like) domains. TBCE folds alpha-tubulin and promotes alpha/beta dimerization.

New interacting partners of the F-box protein Ufo1 of yeast.

The yeast F-box protein Ufo1 recruits proteins for ubiquitylation by the SCF ubiquitin ligase complex preparing them for proteasomal degradation. Ufo1 has a role in maintenance of genome stability; its substrates include Ho endonuclease and Rad30 polymerase of error-prone DNA repair. Ufo1 is an unusual F-box protein, as it has three ubiquitin interacting motifs (UIMs).

Nuclear export of Ho endonuclease of yeast via Msn5.

Exportin-5, an evolutionarily conserved nuclear export factor of the beta-karyopherin family, exports phosphorylated proteins and small noncoding RNAs. Msn5, the yeast ortholog, exports primarily phosphorylated cargoes including Ho endonuclease and a number of transcription factors and regulatory proteins. The Msn5-mediated nuclear export of Ho is dependent on phosphorylation of Thr225 by kinases of the DNA damage response pathway.

The F-box protein, Ufo1, maintains genome stability by recruiting the yeast mating switch endonuclease, Ho, for rapid proteasome degradation.

We describe a unique E3, the F-box protein, Ufo1, of yeast. Ufo1 recruits the mating switch endonuclease, Ho, to the SCF complex for ubiquitylation. In addition to the F-box and WD40 protein-protein interaction domains found in all F-box proteins, Ufo1 has a unique domain comprising multiple copies of the ubiquitin-interacting motif.

Nuclear import of ho endonuclease utilizes two nuclear localization signals and four importins of the ribosomal import system.

Activity of Ho, the yeast mating switch endonuclease, is restricted to a narrow time window of the cell cycle. Ho is unstable and despite being a nuclear protein is exported to the cytoplasm for proteasomal degradation. We report here the molecular basis for the highly efficient nuclear import of Ho and the relation between its short half-life and passage through the nucleus.

Unique role for the UbL-UbA protein Ddi1 in turnover of SCFUfo1 complexes.

SCF complexes are E3 ubiquitin-protein ligases that mediate degradation of regulatory and signaling proteins and control G1/S cell cycle progression by degradation of G1 cyclins and the cyclin-dependent kinase inhibitor, Sic1. Interchangeable F-box proteins bind the core SCF components; each recruits a specific subset of substrates for ubiquitylation. The F-box proteins themselves are rapidly turned over by autoubiquitylation, allowing rapid recycling of SCF complexes.

The DNA damage-inducible UbL-UbA protein Ddi1 participates in Mec1-mediated degradation of Ho endonuclease.

Ho endonuclease initiates a mating type switch by making a double-strand break at the mating type locus, MAT. Ho is marked by phosphorylation for rapid destruction by functions of the DNA damage response, MEC1, RAD9, and CHK1. Phosphorylated Ho is recruited for ubiquitylation via the SCF ubiquitin ligase complex by the F-box protein, Ufo1.

Proteasome plasticity.

The 26S proteasome is responsible for regulated proteolysis of most intracellular proteins yet the focus of intense regulatory action itself. Proteasome abundance is responsive to cell needs or stress conditions, and dynamically localized to concentrations of substrates. Proteasomes are continually assembled and disassembled, and their subunits subject to a variety of posttranslational modifications.

Homology modeling and mutational analysis of Ho endonuclease of yeast.

Ho endonuclease is a LAGLIDADG homing endonuclease that initiates mating-type interconversion in yeast. Ho is encoded by a free-standing gene but shows 50% primary sequence similarity to the intein (protein-intron encoded) PI-SceI. Ho is unique among LAGLIDADG endonucleases in having a 120-residue C-terminal putative zinc finger domain.

DNA damage response-mediated degradation of Ho endonuclease via the ubiquitin system involves its nuclear export.

Yeast mating switch Ho endonuclease is rapidly degraded by the ubiquitin system and this depends on the DNA damage response functions, MEC1, RAD9, and CHK1. A PEST sequence marks Ho for degradation. Here we show that the novel F-box receptor, Ufo1, recruits phosphorylated Ho for degradation.

Stable chloroplast transformation of the unicellular red alga Porphyridium species.

Red algae are extremely attractive for biotechnology because they synthesize accessory photosynthetic pigments (phycobilins and carotenoids), unsaturated fatty acids, and unique cell wall sulfated polysaccharides. We report a high-efficiency chloroplast transformation system for the unicellular red microalga Porphyridium sp. This is the first genetic transformation system for Rhodophytes and is based on use of a mutant form of the gene encoding acetohydroxyacid synthase [AHAS(W492S)] as a dominant selectable marker.

Organelle differentiation in the chick blastoderm during hypoblast formation.

The ultrastructure of the chick blastoderm was examined at three developmental stages, from an unincubated single-layered system through hypoblast advancement to full hypoblast formation.With the onset of incubation the nucleolus changes from a loose network of intermingled pars fibrosa and pars granulosa into a compact body with a definite matrix material.The endoplasmic reticulum, mitochondria, and Golgi complex increase in complexity and volume.