Molecular basis for transposase activation by a dedicated AAA+ ATPase.

Transposases drive chromosomal rearrangements and the dissemination of drug-resistance genes and toxins1-3. Although some transposases act alone, many rely on dedicated AAA+ ATPase subunits that regulate site selectivity and catalytic function through poorly understood mechanisms. Using IS21 as a model transposase system, we show how an ATPase regulator uses nucleotide-controlled assembly and DNA deformation to enable structure-based site selectivity, transposase recruitment, and activation and integration. Solution and cryogenic electron microscopy studies show that the IstB ATPase self-assembles into an autoinhibited pentamer of dimers that tightly curves target DNA into a half-coil. Two of these decamers dimerize, which stabilizes the target nucleic acid into a kinked S-shaped configuration that engages the IstA transposase at the interface between the two IstB oligomers to form an approximately 1 MDa transpososome complex. Specific interactions stimulate regulator ATPase activity and trigger a large conformational change on the transposase that positions the catalytic site to perform DNA strand transfer. These studies help explain how AAA+ ATPase regulators-which are used by classical transposition systems such as Tn7, Mu and CRISPR-associated elements-can remodel their substrate DNA and cognate transposases to promote function.

IS21 family transposase cleaved donor complex traps two right-handed superhelical crossings.

Transposases are ubiquitous enzymes that catalyze DNA rearrangement events with broad impacts on gene expression, genome evolution, and the spread of drug-resistance in bacteria. Here, we use biochemical and structural approaches to define the molecular determinants by which IstA, a transposase present in the widespread IS21 family of mobile elements, catalyzes efficient DNA transposition. Solution studies show that IstA engages the transposon terminal sequences to form a high-molecular weight complex and promote DNA integration. A 3.4 Šresolution structure of the transposase bound to transposon ends corroborates our biochemical findings and reveals that IstA self-assembles into a highly intertwined tetramer that synapses two supercoiled terminal inverted repeats. The three-dimensional organization of the IstA•DNA cleaved donor complex reveals remarkable similarities with retroviral integrases and classic transposase systems, such as Tn7 and bacteriophage Mu, and provides insights into IS21 transposition.

The type V myosin-containing complex HUM is a RAB11 effector powering movement of secretory vesicles.

In the apex-directed RAB11 exocytic pathway of Aspergillus nidulans, kinesin-1/KinA conveys secretory vesicles (SVs) to the hyphal tip, where they are transferred to the type V myosin MyoE. MyoE concentrates SVs at an apical store located underneath the PM resembling the presynaptic active zone. A rod-shaped RAB11 effector, UDS1, and the intrinsically disordered and coiled-coil HMSV associate with MyoE in a stable HUM (HMSV-UDS1-MyoE) complex recruited by RAB11 to SVs through an interaction network involving RAB11 and HUM components, with the MyoE globular tail domain (GTD) binding both HMSV and RAB11-GTP and RAB11-GTP binding both the MyoE-GTD and UDS1. UDS1 bridges RAB11-GTP to HMSV, an avid interactor of the MyoE-GTD. The interaction between the UDS1-HMSV sub-complex and RAB11-GTP can be reconstituted in vitro. Ablating UDS1 or HMSV impairs actomyosin-mediated transport of SVs to the apex, resulting in spreading of RAB11 SVs across the apical dome as KinA/microtubule-dependent transport gains prominence.

Improved cancer-related fatigue in a randomised clinical trial: methylphenidate no better than placebo.

INTRODUCTION: Methylphenidate is a psychostimulant drug used to treat fatigue in patients with advanced cancer, for which there is no gold standard of treatment. OBJECTIVE: To explore the efficacy of methylphenidate in the relief of fatigue in patients with advanced cancer. MATERIALS AND METHODS: A randomised double-blind placebo-controlled multicentre clinical trial, stratified according to the intensity of fatigue. The treatment was considered effective if the improvement in mean fatigue intensity between baseline values and day 6 was significantly higher in the methylphenidate group than in the placebo group. The responses were measured using the Edmonton Symptoms Assessment System (ESAS) and the Functional Assessment of Cancer Therapy-Fatigue (FACT-F) scales. RESULTS: 35 patients received placebo and 42 patients received methylphenidate. The populations of both groups were homogeneous. Patients receiving methylphenidate did not exhibit statistically significant improvement of fatigue in comparison to patients receiving placebo (p=0.52). The mean improvement of fatigue (ESAS) on day 6 was -1.9 (±2.5) in the placebo group, and -2.3 (±2.6) in the methylphenidate group (p=0.52). The results obtained with the FACT-F were congruent with those obtained by the ESAS. The responses in patients with severe fatigue were -2.4 (±2.9) in the placebo group and -3.4 (±2.5) in the methylphenidate group; the difference was not statistically significant (p=0.3). CONCLUSION: Methylphenidate was not more efficient than placebo to treat cancer-related fatigue. Fatigue improved significantly after 3 days of treatment and was stabilised on day 6, both with placebo and methylphenidate. The side effects of methylphenidate were mild and infrequent. TRIAL REGISTRATION NUMBER: EudraCT Registry (2008-002171-27).

Prevalence and characterization of breakthrough pain in patients with cancer in Spain: the CARPE-DIO study.

We aimed to evaluate the prevalence, characteristics and impact of breakthrough pain (BTP) in patients with cancer attending the main specialties involved in the diagnosis and management of BTP in Spain using a multicenter, observational, cross-sectional, multidisciplinary study. Investigators had to record all patients seen at the clinic during 1 month, determine whether the patients had cancer pain, and apply the Davies algorithm to ascertain whether the patients were suffering from BTP. Of the 3,765 patients with cancer, 1,117 (30%) had cancer-related pain, and of these patients, 539 had BTP (48%, 95%CI:45-51). The highest prevalence was found in patients from palliative care (61%, 95%CI:54-68), and the lowest was found in those from hematology (25%, 95%CI:20-31). Prevalence varied also according to sex and type of tumor. According to the Alberta Breakthrough Pain Assessment Tool duration, timing, frequency, location, severity, quality, causes, and predictability of the BTP varied greatly among these patients. BTP was moderate (Brief Pain Inventory [BPI]-severity median score = 5.3), and pain interference was moderate (BPI-interference median score = 6.1) with a greater interference with normal work, general activity, and enjoyment of life. Patients with BTP showed a mean ± standard deviation score of 28.5 ± 8.0 and 36.9 ± 9.5 in the physical and mental component, respectively, of the SF-12 questionnaire. In conclusion, prevalence of BTP among patients exhibiting cancer-related pain is high. Clinical presentation is heterogeneous, and therefore, BTP cannot be considered as a single entity. However, uniformly BTP has an important impact on a patient's functionality, which supports the need for early detection and treatment.