The cyclin-dependent kinase (CDK) inhibitor p27 is degraded in late G1 phase by the ubiquitin pathway, allowing CDK activity to drive cells into S phase. Ubiquitinylation of p27 requires its phosphorylation at Thr 187 (refs 3, 4) and subsequent recognition by S-phase kinase associated protein 2 (Skp2; refs 5-8), a member of the F-box family of proteins that associates with Skp1, Cul-1 and ROC1/Rbx1 to form an SCF ubiquitin ligase complex. However, in vitro ligation of p27 to ubiquitin could not be reconstituted by known purified components of the SCFSkp2 complex. Here we show that the missing factor is CDK subunit 1 (Cks1), which belongs to the highly conserved Suc1/Cks family of proteins that bind to some CDKs and phosphorylated proteins and are essential for cell-cycle progression. Human Cks1, but not other members of the family, reconstitutes ubiquitin ligation of p27 in a completely purified system, binds to Skp2 and greatly increases binding of T187-phosphorylated p27 to Skp2. Our results represent the first evidence that an SCF complex requires an accessory protein for activity as well as for binding to its phosphorylated substrate.

The cyclin-dependent kinase inhibitor p21Cip1 has important roles in the control of cell proliferation, differentiation, senescence, and apoptosis. It has been observed that p21 is a highly unstable protein, but the mechanisms of its degradation remained unknown. We show here that p21 is a good substrate for an SCF (Skp1-Cullin1-F-box protein) ubiquitin ligase complex, which contains the F-box protein Skp2 (S phase kinase-associated protein 2) and the accessory protein Cks1 (cyclin kinase subunit 1). A similar ubiquitin ligase complex has been previously shown to be involved in the degradation of a related cyclin-dependent kinase inhibitor, p27Kip1 . The levels of Skp2 oscillate in the cell cycle, reaching a maximum in S phase. The ubiquitylation of p21 in vitro required the supplementation of all components of the SCF complex as well as of Cks1 and Cdk2-cyclin E. The protein kinase Cdk2-cyclin E acts both by the phosphorylation of p21 on Ser-130 and by the formation of a complex with p21, which is required for its presentation to the ubiquitin ligase. As opposed to the case of p27, the phosphorylation of p21 stimulates its ubiquitylation but is not absolutely required for this process. Levels of p21 are higher in Skp2؊/؊ mouse embryo fibroblasts than in wild-type fibroblasts in the S phase, and the rates of the degradation of p21 are slower in cells that lack Skp2. It is suggested that SCF Skp2 participates in the degradation of p21 in the S phase.

The activity of cullin-containing ubiquitin protein ligase complexes is stimulated by linkage to cullin of the ubiquitin-like protein Nedd8 (''neddylation''). Neddylation is inhibited by the tight binding of cullins to CAND1 (cullin-associated and neddylation-dissociated 1) protein, and Nedd8 is removed from cullins by specific isopeptidase activity of the COP9͞signalosome (CSN) complex. The mechanisms that regulate neddylation and deneddylation of cullins were unknown. We examined this problem for the case of SCF Skp2 , a cullin1 (Cul1)-containing ubiquitin ligase complex that contains the S phase-associated protein Skp2 as the substratebinding F-box protein subunit. SCF Skp2 targets for degradation the cyclin-dependent kinase (cdk) inhibitor p27 in the G 1-to-S phase transition, a process that requires its phosphorylation and binding to cdk2-cyclin E. Because levels of Skp2, cyclin E, and the accessory protein Cks1 (cyclin kinase subunit 1) all rise at the end of G 1 phase, it seemed possible that the neddylation of Cul1 in SCF Skp2 is regulated by the availability of the F-box protein and͞or the substrate. We found that the supplementation of Skp2-Skp1 and substrate (along with further components necessary for substrate presentation to the ubiquitin ligase) to extracts of HeLa cells synergistically increased levels of neddylated Cul1. Skp2-Skp1 abrogates the inhibitory influence of CAND1 on the neddylation of Cul1 by promoting the dissociation of the cullin-CAND1 complex, whereas substrate, together with substrate-presenting components, prevents the action of CSN to deneddylate cullin. We propose a sequence of events in which the increased availability of Skp2 and substrate in the transition of cells to S phase promotes the neddylation and assembly of the SCF Skp2 ubiquitin ligase complex.cell cycle ͉ Nedd8

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In this randomized controlled trial, anakinra appears to be an effective and safe treatment for colchicine-resistant FMF.

The diagnosis of giant cell arteritis (GCA) is based on clinical grounds and confirmed by characteristic histological findings on temporal artery biopsy (TAB). Patients may be diagnosed with GCA based on clinical grounds only, despite negative histological findings. We aimed to investigate which baseline clinical and laboratory features best predict an ultimate diagnosis of giant cell arteritis among patients referred to TAB. We retrospectively analyzed 224 patients who underwent TAB in our hospital between 2000 and 2014. Patients were diagnosed with GCA if TAB was positive for GCA, or by clinical grounds only despite a negative biopsy, provided they fulfilled the American College of Rheumatology 1990 criteria. Baseline clinical and laboratory features were obtained from medical records. Predictors of an ultimate GCA diagnosis were investigated. Overall, 82 patients were diagnosed with GCA-57 had histological evidence of GCA and 25 were diagnosed with GCA despite a negative biopsy. One hundred and forty-two patients were not diagnosed with GCA. Predictors of an eventual diagnosis of GCA in a multivariate logistic regression analysis were headache (OR = 6; p < 0.001), jaw claudication (OR 4.5; p = 0.007), erythrocyte sedimentation rate (ESR) (OR = 1.5; p = 0.032) and platelet count (OR = 1.74; p = 0.004). Among patients referred to TAB, headache, jaw claudication, ESR, and thrombocyte levels are predictors for an ultimate diagnosis of GCA. These clinical and laboratory features should be considered when contemplating the diagnosis and treatment of GCA.

Anaemia is more common in diabetic patients even when eGFR > 60 mL/min.

Uric acid (UA) is associated with atherosclerosis, and coronary artery calcium (CAC) is a marker of atherosclerosis. The authors studied the association between UA and CAC. A total of 663 asymptomatic patients (564 men; mean age, 55±7 years) were evaluated for the presence of CAC. The study population was divided into three tertiles according to their UA levels, and the prevalence of CAC was compared between the tertiles. CAC was detected in 349 (53%) patients. Levels of UA were significantly higher in those with CAC than in those without CAC (5.6+1.2 vs 5.3+1.3; P=.003). The odds ratio for the presence of CAC in the highest vs lowest UA tertile was 1.72 (95% confidence interval, 1.17–2.51). The highest UA tertile remained associated with the presence of CAC after adjustment for known cardiovascular risk factors. The results show that high serum UA levels are associated with the presence of CAC.