A C‐terminally modified ubiquitin (Ub) derivative, ubiquitin vinyl sulfone (UbVS), was synthesized as an active site‐directed probe that irreversibly modifies a subset of Ub C‐terminal hydrolases (UCHs) and Ub‐specific processing proteases (UBPs). Specificity of UbVS for deubiquitylating enzymes (DUBs) is demonstrated not only by inhibition of [125I]UbVS labeling with N‐ethylmaleimide and Ub aldehyde, but also by genetic analysis. [125I]UbVS modifies six of the 17 known and putative yeast deubiquitylating enzymes (Yuh1p, Ubp1p, Ubp2p, Ubp6p, Ubp12p and Ubp15p), as revealed by analysis of corresponding mutant strains. In mammalian cells, greater numbers of polypeptides are labeled, most of which are likely to be DUBs. Using [125I]UbVS as a probe, we report the association of an additional DUB with the mammalian 26S proteasome. In addition to the 37 kDa enzyme reported to be part of the 19S cap, we identified USP14, a mammalian homolog of yeast Ubp6p, as being bound to the proteasome. Remarkably, labeling of 26S‐associated USP14 with [125I]UbVS is increased when proteasome function is impaired, suggesting functional coupling between the activities of USP14 and the proteasome.
An overview of proceedings, findings, and recommendations from the workshop on "Advancing Symptom Science Through Symptom Cluster Research" sponsored by the National Institute of Nursing Research (NINR) and the Office of Rare Diseases Research, National Center for Advancing Translational Sciences, is presented. This workshop engaged an expert panel in an evidenced-based discussion regarding the state of the science of symptom clusters in chronic conditions including cancer and other rare diseases. An interdisciplinary working group from the extramural research community representing nursing, medicine, oncology, psychology, and bioinformatics was convened at the National Institutes of Health. Based on expertise, members were divided into teams to address key areas: defining characteristics of symptom clusters, priority symptom clusters and underlying mechanisms, measurement issues, targeted interventions, and new analytic strategies. For each area, the evidence was synthesized, limitations and gaps identified, and recommendations for future research delineated. The majority of findings in each area were from studies of oncology patients. However, increasing evidence suggests that symptom clusters occur in patients with other chronic conditions (eg, pulmonary, cardiac, and end-stage renal disease). Nonetheless, symptom cluster research is extremely limited and scientists are just beginning to understand how to investigate symptom clusters by developing frameworks and new methods and approaches. With a focus on personalized care, an understanding of individual susceptibility to symptoms and whether a "driving" symptom exists that triggers other symptoms in the cluster is needed. Also, research aimed at identifying the mechanisms that underlie symptom clusters is essential to developing targeted interventions.Patients with chronic conditions, such as cancer and other rare diseases, experience an array of multiple co-occurring symptoms (eg, pain, fatigue, sleep disturbance). When these symptoms remain underdiagnosed and undertreated, they have a negative impact on patient-reported outcomes (PROs) including functional performance, cognitive status, and quality of life (QOL). A reduction in symptom burden in these patients has the potential to improve their capacity to live well over their entire lives. To achieve this goal, a transformation is needed in how multiple co-occurring symptoms are assessed and managed in order to improve patient outcomes and stimulate a reduction in health care utilization and costs. A strategic plan that advances REVIEW
To dissect the requirements of membrane protein degradation from the ER, we expressed the mouse major histocompatibility complex class I heavy chain H-2K(b) in yeast. Like other proteins degraded from the ER, unassembled H-2K(b) heavy chains are not transported to the Golgi but are degraded in a proteasome-dependent manner. The overexpression of H-2K(b) heavy chains induces the unfolded protein response (UPR). In yeast mutants unable to mount the UPR, H-2K(b) heavy chains are greatly stabilized. This defect in degradation is suppressed by the expression of the active form of Hac1p, the transcription factor that upregulates UPR-induced genes. These results indicate that induction of the UPR is required for the degradation of protein substrates from the ER.
Ribonucleotide reductases catalyze the formation of deoxyribonucleotides by the reduction of the corresponding ribonucleotides. Eukaryotic ribonucleotide reductases are ␣ 2  2 tetramers; each of the larger, ␣ subunits possesses binding sites for substrate and allosteric effectors, and each of the smaller,  subunits contains a binuclear iron complex. The iron complex interacts with a specific tyrosine residue to form a tyrosyl free radical which is essential for activity. Previous work has identified two genes in the yeast Saccharomyces cerevisiae, RNR1 and RNR3, that encode ␣ subunits and one gene, RNR2, that encodes a  subunit. Here we report the identification of a second gene from this yeast, RNR4, that encodes a protein with significant similarity to the -subunit proteins. The phenotype of rnr4 mutants is consistent with that expected for a defect in ribonucleotide reductase; rnr4 mutants are supersensitive to the ribonucleotide reductase inhibitor hydroxyurea and display an S-phase arrest at their restrictive temperature. rnr4 mutant extracts are deficient in ribonucleotide reductase activity, and this deficiency can be remedied by the addition of exogenous Rnr4p. As is the case for the other RNR genes, RNR4 is induced by agents that damage DNA. However, Rnr4p lacks a number of sequence elements thought to be essential for iron binding, and mutation of the critical tyrosine residue does not affect Rnr4p function. These results suggest that Rnr4p is catalytically inactive but, nonetheless, does play a role in the ribonucleotide reductase complex.Ribonucleotide reductases catalyze the formation of deoxyribonucleotides by the reduction of the corresponding ribonucleotides. Three classes of ribonucleotide reductases have been well characterized (24). Class I enzymes are found in all eukaryotes and some prokaryotes. The best-studied class I enzyme is the Escherichia coli ribonucleotide reductase (10, 30), an ␣ 2  2 tetramer that can be decomposed to two catalytically inactive homodimers, R1 (␣ 2 ) and R2 ( 2 ). Each of the larger ␣ subunits possesses binding sites for substrate and allosteric effectors and also contains several redox-active cysteine residues. Each of the smaller  subunits contains a binuclear Fe(III) complex. The X-ray structure of E. coli R2 reveals that the iron ions are bridged by both an O 2Ϫ ion and the carboxyl group of a glutamate residue (22). Each iron is further liganded by two carboxyl oxygen atoms from aspartate or glutamate residues, a histidine N␦ residue, and a water molecule. The recently solved structure of the mouse R2 protein indicates that the iron-binding center of eukaryotic proteins is similar to that of the E. coli protein (17). The iron complex interacts with a specific tyrosine residue to form a tyrosyl free radical which is essential for activity. The enzyme is inhibited by hydroxyurea, which specifically quenches the tyrosyl radical (19).Amino acid sequence alignments of the class 1 R2 proteins from different species identify 16 residues that are conserved in a...
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