Mechanism of USP7/HAUSP activation by its C-terminal ubiquitin-like domain and allosteric regulation by GMP-synthetase.

The ubiquitin-specific protease USP7/HAUSP regulates p53 and MDM2 levels, and cellular localization of FOXO4 and PTEN, and hence is critically important for their role in cellular processes. Here we show how the 64 kDa C-terminal region of USP7 can positively regulate deubiquitinating activity. We present the crystal structure of this USP7/HAUSP ubiquitin-like domain (HUBL) comprised of five ubiquitin-like (Ubl) domains organized in 2-1-2 Ubl units. The last di-Ubl unit, HUBL-45, is sufficient to activate USP7, through binding to a “switching” loop in the catalytic domain, which promotes ubiquitin binding and increases activity 100-fold. This activation can be enhanced allosterically by the metabolic enzyme GMPS. It binds to the first three Ubl domains (HUBL-123) and hyperactivates USP7 by stabilization of the HUBL-45-dependent active stat

Native mass spectrometry provides direct evidence for DNA mismatch-induced regulation of asymmetric nucleotide binding in mismatch repair protein MutS

The DNA mismatch repair protein MutS recognizes mispaired bases in DNA and initiates repair in an ATP-dependent manner. Understanding of the allosteric coupling between DNA mismatch recognition and two asymmetric nucleotide binding sites at opposing sides of the MutS dimer requires identification of the relevant MutS.mmDNA.nucleotide species. Here, we use native mass spectrometry to detect simultaneous DNA mismatch binding and asymmetric nucleotide binding to Escherichia coli MutS. To resolve the small differences between macromolecular species bound to different nucleotides, we developed a likelihood based algorithm capable to deconvolute the observed spectra into individual peaks. The obtained mass resolution resolves simultaneous binding of ADP and AMP.PNP to this ABC ATPase in the absence of DNA. Mismatched DNA regulates the asymmetry in the ATPase sites; we observe a stable DNA-bound state containing a single AMP.PNP cofactor. This is the first direct evidence for such a postulated mismatch repair intermediate, and showcases the potential of native MS analysis in detecting mechanistically relevant reaction intermediates

K27-linked diubiquitin inhibits UCHL3 via an unusual kinetic trap

Functional analysis of lysine 27-linked ubiquitin chains ((K27)Ub) is difficult due to the inability to make them through enzymatic methods and due to a lack of model tools and substrates. Here we generate a series of ubiquitin (Ub) tools to study how the deubiquitinase UCHL3 responds to (K27)Ub chains in comparison to lysine 63-linked chains and mono-Ub. From a crystal structure of a complex between UCHL3 and synthetic (K27)Ub(2), we unexpectedly discover that free (K27)Ub(2) and (K27)Ub(2)-conjugated substrates are natural inhibitors of UCHL3. Using our Ub tools to profile UCHL3's activity, we generate a quantitative kinetic model of the inhibitory mechanism and we find that (K27)Ub(2) can inhibit UCHL3 covalently, by binding to its catalytic cysteine, and allosterically, by locking its catalytic loop tightly in place. Based on this inhibition mechanism, we propose that UCHL3 and (K27)Ub chains likely sense and regulate each other in cells.Chemical Immunolog

Gas phase characterization of the noncovalent quaternary structure of Cholera toxin and the Cholera toxin B subunit pentamer

Cholera toxin (CTx) is an AB5 cytotonic protein that has medical relevance in cholera and as a novel mucosal adjuvant. Here, we report an analysis of the noncovalent homopentameric complex of CTx B chain (CTx B5) using electrospray ionization triple quadrupole mass spectrometry and tandem mass spectrometry and the analysis of the noncovalent hexameric holotoxin usingelectrospray ionization time-of-flight mass spectrometry over a range of pH values that correlate with those encountered by this toxin after cellular uptake. We show that noncovalent interactions within the toxin assemblies were maintained under both acidic and neutral conditions in the gas phase. However, unlike the related Escherichia coli Shiga-like toxin B5 pentamer (SLTx B), the CTx B5 pentamer was stable at low pH, indicating that additional interactions must be present within the latter. Structural comparison of the CTx B monomer interface reveals an additional α-helix that is absent in the SLTx B monomer. In silico energy calculations support interactions between this helix and the adjacent monomer. These data provide insight into the apparent stabilization of CTx B relative to SLTx B

Transient transfection coupled to baculovirus infection for rapid protein expression screening in insect cells

Baculovirus infected insect cells are widely used for heterologous protein expression. Despite the power of this system, the use of baculovirus techniques for protein expression screening is hampered by the time and resources needed to generate each recombinant baculovirus. Here, we show that a transfection/infection based expression system is suitable for screening of expression constructs in insect cells and represents a valid alternative to other traditional screening methodologies using recombinant baculovirus. The described method is based on gene delivery by transfection coupled to the induction of protein expression by non-recombinant baculovirus infection. Vectors that control expression by a combination of the baculovirus promoters . ie1 and . p10 and the enhancer element . hr5 are among the ones suitable for this method. Infection with non-recombinant baculovirus drastically increases the basal activity of these elements, leading to protein over-expression. Multiple vectors can be simultaneously co-transfected/infected, making transfection/infection amenable for screening of multiple co-expressed proteins and protein complexes. Taken together, our results prove that the transfection/infection protocol is a valid and innovative approach for increasing speed and reducing costs of protein expression screening for structural and functional studies. © 2012 Elsevier Inc.

USP48 restrains resection by site-specific cleavage of the BRCA1 ubiquitin mark from H2A

BRCA1 ligase activity is tightly regulated to maintain genome stability and confer DNA double strand repair. Here the authors identify USP48 as a H2A deubiquitinating enzyme that acts as a BRCA1 E3 ligase antagonist and characterize its role during DNA repair

The Consumer Quality Index Hip Knee Questionnaire measuring patients' experiences with quality of care after a total hip or knee arthroplasty

<p>Abstract</p> <p>Background</p> <p>The Dutch Consumer Quality Index Hip Knee Questionnaire (CQI Hip Knee) was used to assess patients' experiences with and evaluations of quality of care after a total hip (THA) or total knee arthroplasty (TKA). The aim of this study is to evaluate the construct validity and internal consistency reliability of this new instrument and to assess its ability to measure differences in quality of care between hospitals.</p> <p>Methods</p> <p>Survey data of 1,675 subjects who underwent a THA or TKA were used to evaluate the psychometric properties. Exploratory factor analyses were performed and item-total correlations and inter-factor correlations were calculated to assess the construct validity of the instrument. Reliability analyses included tests of internal consistency (Cronbach's alpha coefficients). Finally, multilevel analyses were performed to assess the ability of the instrument to discriminate between hospitals in quality of care.</p> <p>Results</p> <p>Exploratory factor analyses indicated that the survey consisted of 21 items measuring five aspects of care (i.e. communication with nurses, communication with doctors, communication with general practitioner, communication about new medication, and pain control). Cronbach's alpha coefficients ranged from 0.76 to 0.90 indicating good internal consistency. The survey's ability to discriminate between hospitals was partly supported by multilevel analysis. Two scales (i.e. communication with nurses and communication with doctors) were able to measure differences between hospitals with respect to patients' experiences with quality of care. Logistic multilevel analyses indicated that hospitals explained part of the variation between patients in receiving information.</p> <p>Conclusion</p> <p>These findings suggest that the CQI Hip Knee is reliable and valid for use in Dutch health care. Health care providers or health plans can use this survey to measure patients' experiences with hospital care and to identify variations in care between hospitals.</p

Is the impact of hospital performance data greater in patients who have compared hospitals?

<p>Abstract</p> <p>Background</p> <p>Public information on average has limited impact on patients' hospital choice. However, the impact may be greater in consumers who have compared hospitals prior to their hospital choice. We therefore assessed whether patients who have compared hospitals based their hospital choice mainly on public information, rather than e.g. advice of their general practitioner and consider other information important than patients who have not compared hospitals.</p> <p>Methods</p> <p>337 new surgical patients completed an internet-based questionnaire. They were asked whether they had compared hospitals prior to their hospital choice and which factors influenced their choice. They were also asked to select between four and ten items of hospital information (total: 41 items) relevant for their future hospital choice. These were subsequently used in a hospital choice experiment in which participants were asked to compare hospitals in an Adaptive Choice-Based Conjoint analysis to estimate which of the hospital characteristics had the highest Relative Importance (RI).</p> <p>Results</p> <p>Patients who have compared hospitals more often used public information for their hospital choice than patients who have not compared hospitals (12.7% vs. 1.5%, p < 0.001). However, they still mostly relied on their own (47.9%) and other people's experiences (31%) rather than to base their decision on public information. Both groups valued physician's expertise (RI 20.2 [16.6-24.8] in patients comparing hospitals vs. 16.5 [14.2-18.8] in patients not comparing hospitals) and waiting time (RI 15.1 [10.7-19.6] vs. 15.6 [13.2-17.9] respectively) as most important public information. Patients who have compared hospitals assigned greater importance to information on wound infections (p = 0.010) and respect for patients (p = 0.022), but lower importance to hospital distance (p = 0.041).</p> <p>Conclusion</p> <p>Public information has limited impact on patient's hospital choice, even in patients who have actually compared hospitals prior to hospital choice.</p

Transition of care: experiences and preferences of patients across the primary/secondary interface – a qualitative study

BACKGROUND: Coordination between care providers of different disciplines is essential to improve the quality of care, in particular for patients with chronic diseases. The way in which general practitioners (GP's) and medical specialists interact has important implications for any healthcare system in which the GP plays the role of gatekeeper to specialist care. Patient experiences and preferences have proven to be increasingly important in discussing healthcare policy. The Dutch government initiated the development of a special website with information for patients on performance indicators of hospitals as well as information on illness or treatment.In the present study we focus on the transition of care at the primary - secondary interface with reference to the impact of patients' ability to make choices about their secondary care providers. The purpose of this study is to (a) explore experiences and preferences of patients regarding the transition between primary and secondary care, (b) study informational resources on illness/treatment desired by patients and (c) determine how information supplied could make it easier for the patient to choose between different options for care (hospital or specialist). METHODS: We conducted a qualitative study using semi-structured focus group interviews among 71 patients referred for various indications in the north and west of The Netherlands. RESULTS: Patients find it important that they do not have to wait, that they are taken seriously, and receive adequate and individually relevant information. A lack of continuity from secondary to primary care was experienced. The patient's desire for free choice of type of care did not arise in any of the focus groups. CONCLUSION: Hospital discharge information needs to be improved. The interval between discharge from specialist care and the report of the specialist to the GP might be a suitable performance indicator in healthcare. Patients want to receive information, tailored to their own situation. The need for information, however, is quite variable. Patients do not feel strongly about self-chosen healthcare, contrary to what administrators presently believe