Slx5/Slx8-dependent ubiquitin hotspots on chromatin contribute to stress tolerance

Chromatin is a highly regulated environment, and protein association with chromatin is often controlled by post-translational modifications and the corresponding enzymatic machinery. Specifically, SUMO-targeted ubiquitin ligases (STUbLs) have emerged as key players in nuclear quality control, genome maintenance, and transcription. However, how STUbLs select specific substrates among myriads of SUMOylated proteins on chromatin remains unclear. Here, we reveal a remarkable co-localization of the budding yeast STUbL Slx5/Slx8 and ubiquitin at seven genomic loci that we term "ubiquitin hotspots". Ubiquitylation at these sites depends on Slx5/Slx8 and protein turnover on the Cdc48 segregase. We identify the transcription factor-like Ymr111c/Euc1 to associate with these sites and to be a critical determinant of ubiquitylation. Euc1 specifically targets Slx5/Slx8 to ubiquitin hotspots via bipartite binding of Slx5 that involves the Slx5 SUMO-interacting motifs and an additional, novel substrate recognition domain. Interestingly, the Euc1-ubiquitin hotspot pathway acts redundantly with chromatin modifiers of the H2A.Z and Rpd3L pathways in specific stress responses. Thus, our data suggest that STUbL-dependent ubiquitin hotspots shape chromatin during stress adaptation

Homological Berglund-Hübsch mirror symmetry for curve singularities

Given a two-variable invertible polynomial, we show that its category of maximally-graded matrix factorisations is quasi-equivalent to the Fukaya–Seidel category of its Berglund–Hübsch transpose. This was previously shown for Brieskorn–Pham and D-type singularities by Futaki–Ueda. The proof involves explicit construction of a tilting object on the B‑side, and comparison with a specific basis of Lefschetz thimbles on the A‑side

Reductive chain separation of botulinum A toxin — a prerequisite to its inhibitory action on exocytosis in chromaffin cells

Cleavage of the disulfide bond linking the heavy and the light chains of tetanus toxin is necessary for its inhibitory action on exocytotic release ofcatecholamines from permeabi1ized chromaffin cells [(1989) FEBS Lett. 242, 245-248; (1989) J. Neurochern., in press]. The related botulinum A toxin also consists of a heavy and a light chain linked by a disulfide bond. The actions ofboth neurotoxins on exocytosis were presently compared using streptolysin O-permeabilized bovine adrenal chromaffin cells. Botulinum A toxin inhibited Ca2 +-stimulated catecholamine release from these cells. Addition of dithiothreitollowered the effective doses to values below 5 nM. Under the same conditions, the effective doses of tetanus toxin were decreased by a factor of five. This indicates that the interchain S-S bond of botulinum A toxin must also be split before the neurotoxin can exert its effect on exocytosis

The cytoplasmic poly(A) polymerases GLD-2 and GLD-4 promote general gene expression via distinct mechanisms

Post-transcriptional gene regulation mechanisms decide on cellular mRNA activities. Essential gatekeepers of post-transcriptional mRNA regulation are broadly conserved mRNA-modifying enzymes, such as cytoplasmic poly(A) polymerases (cytoPAPs). Although these non-canonical nucleotidyltransferases efficiently elongate mRNA poly(A) tails in artificial tethering assays, we still know little about their global impact on poly(A) metabolism and their individual molecular roles in promoting protein production in organisms. Here, we use the animal model Caenorhabditis elegans to investigate the global mechanisms of two germline-enriched cytoPAPs, GLD-2 and GLD-4, by combining polysome profiling with RNA sequencing. Our analyses suggest that GLD-2 activity mediates mRNA stability of many translationally repressed mRNAs. This correlates with a general shortening of long poly(A) tails in gld-2-compromised animals, suggesting that most if not all targets are stabilized via robust GLD-2-mediated polyadenylation. By contrast, only mild polyadenylation defects are found in gld-4-compromised animals and few mRNAs change in abundance. Interestingly, we detect a reduced number of polysomes in gld-4 mutants and GLD-4 protein co-sediments with polysomes, which together suggest that GLD-4 might stimulate or maintain translation directly. Our combined data show that distinct cytoPAPs employ different RNA-regulatory mechanisms to promote gene expression, offering new insights into translational activation of mRNAs

Task difficulty and life changes among stroke family caregivers: relationship to depressive symptoms

OBJECTIVES: To investigate differences in stroke caregiver task difficulty and life changes based on level of caregiver depressive symptoms, and to estimate probabilities among task difficulty and life change items. DESIGN: Descriptive analysis of baseline data from an ongoing stroke caregiver intervention trial. SETTING: Hospitals and rehabilitation facilities. PARTICIPANTS: Caregivers (N=242; 78.6% women; 47.7% spouses; 71.8% white; mean age, 54.2±12.1y) caring for stroke survivors within 8 weeks of discharge to home. INTERVENTIONS: Not applicable. MAIN OUTCOME MEASURES: Baseline measures for task difficulty (Oberst Caregiving Burden Scale) and life changes (Bakas Caregiving Outcomes Scale) were compared based on level of depressive symptoms (Patient Health Questionnaire-9 [PHQ-9] scores <5 means no depressive symptoms; n=126; PHQ-9 scores ≥5 means mild to severe depressive symptoms, n=116). Mean scores were analyzed using general linear modeling, with item analyses using logistic regression and the Benjamini-Hochberg method to control type I error inflation. RESULTS: Caregivers with mild to severe depressive symptoms have greater difficulty with tasks and worse life changes than those with no depressive symptoms (P<.001). Odds ratios were highest for the task of arranging care while away and for negative life changes (eg, addressing self-esteem, coping with stress, physical health). CONCLUSIONS: Findings underscore the importance of depressive symptom screening for stroke caregivers during or shortly after discharge. Assisting caregivers with depressive symptoms to arrange for respite care and addressing negative physical and psychological changes may be priority areas for future interventions