Cohesin Releases DNA through Asymmetric ATPase-Driven Ring Opening

Cohesin stably holds together the sister chromatids from S phase until mitosis. To do so, cohesin must be protected against its cellular antagonist Wapl. Eco1 acetylates cohesin's Smc3 subunit, which locks together the sister DNAs. We used yeast genetics to dissect how Wapl drives cohesin from chromatin and identified mutants of cohesin that are impaired in ATPase activity but remarkably confer robust cohesion that bypasses the need for the cohesin protectors Eco1 in yeast and Sororin in human cells. We uncover a functional asymmetry within the heart of cohesin's highly conserved ABC-like ATPase machinery and find that both ATPase sites contribute to DNA loading, whereas DNA release is controlled specifically by one site. We propose that Smc3 acetylation locks cohesin rings around the sister chromatids by counteracting an activity associated with one of cohesin's two ATPase sites. Tight regulation of DNA entrapment and release by the cohesin complex is crucial for its multiple cellular functions. Elbatsh et al. find that cohesin's release from DNA requires an activity associated with one of its ATPase sites, whereas both sites control cohesin's loading onto DNA

Architecture of the Human Ndc80-Hec1 Complex, a Critical Constituent of the Outer Kinetochore

The Ndc80 complex is a constituent of the outer plate of the kinetochore and plays a critical role in establishing the stable kinetochore-microtubule interactions required for chromosome segregation in mitosis. The Ndc80 complex is evolutionarily conserved and contains the four subunits Spc24, Spc25, Nuf2, and Ndc80 (whose human homologue is called Hec1). All four subunits are predicted to contain globular domains and extensive coiled coil regions. To gain an insight into the organization of the human Ndc80 complex, we reconstituted it using recombinant methods. The hydrodynamic properties of the recombinant Ndc80 complex are identical to those of the endogenous HeLa cell complex and are consistent with a 1:1:1:1 stoichiometry of the four subunits and a very elongated shape. Two tight Hec1-Nuf2 and Spc24-Spc25 subcomplexes, each stabilized by a parallel heterodimeric coiled coil, maintain this organization. These subcomplexes tetramerize via an interaction of the C- and N-terminal portions of the Hec1-Nuf2 and Spc24-Spc25 coiled coils, respectively. The recombinant complex displays normal kinetochore localization upon injection in HeLa cells and is therefore a faithful copy of the endogenous Ndc80 complex

Caffeine suppresses homologous recombination through interference with RAD51-mediated joint molecule formation

Caffeine is a widely used inhibitor of the protein kinases that play a central role in the DNA damage response. We used chemical inhibitors and genetically deficient mouse embryonic stem cell lines to study the role of DNA damage response in stable integration of the transfected DNA and found that caffeine rapidly, efficiently and reversibly inhibited homologous integration of the transfected DNA as measured by several homologous recombination-mediated gene-targeting assays. Biochemical and structural biology experiments revealed that caffeine interfered with a pivotal step in homologous recombination, homologous joint molecule formation, through increasing interactions of the RAD51 nucleoprotein filament with non-homologous DNA. Our results suggest that recombination pathways dependent on extensive homology search are caffeine-sensitive and stress the importance of considering direct checkpoint-independent mechanisms in the interpretation of the effects of caffeine on DNA repair

Haemodynamic and clinical effects of ularitide in decompensated heart failure

Aims Ularitide is a synthetic form of urodilatin, a natriuretic peptide produced in the kidney with vasodilating, natriuretic, and diuretic effects, that offers promise for the management of decompensated heart failure (DHF). We assessed the efficacy and safety of ularitide in treating patients with DHF. Methods and results In this Phase II randomized, double-blind, placebo-controlled trial, 221 DHF patients received either placebo (n=53) or ularitide at 7.5 ng/kg/min (n=60), 15 ng/kg/min (n=53), or 30 ng/kg/min (n=55) as a 24-h continuous infusion. At 6 h, ularitide demonstrated a significant decrease in pulmonary capillary wedge pressure (P=0.052, P=0.000004, P=0.000002, respectively) and improved dyspnoea score in the 7.5, 15, and 30 ng/kg/min ularitide group (P=0.0026, P=0.0026, P=0.0013, respectively). Ularitide reduced systemic vascular resistance and increased cardiac index for the 15 and 30 ng/kg/min groups (P=0.017, P=0.00002, respectively). Systolic blood pressure (BP) decreased dose dependency. Heart rate and serum creatinine were unchanged through day 3. Most frequently reported drug-related adverse events through day 3 in all ularitide groups were dose-dependent BP decrease and hypotension. Conclusion Ularitide lowered cardiac filling pressures and improved dyspnoea without apparent early deleterious effects on renal function in DHF patients. These results suggest that ularitide may play a role in the management of DHF

Molecular basis of microhomology-mediated end-joining by purified full-length Polθ

DNA polymerase θ (Polθ) is a unique polymerase-helicase fusion protein that promotes microhomology-mediated end-joining (MMEJ) of DNA double-strand breaks (DSBs). How full-length human Polθ performs MMEJ at the molecular level remains unknown. Using a biochemical approach, we find that the helicase is essential for Polθ MMEJ of long ssDNA overhangs which model resected DSBs. Remarkably, Polθ MMEJ of ssDNA overhangs requires polymerase-helicase attachment, but not the disordered central domain, and occurs independently of helicase ATPase activity. Using single-particle microscopy and biophysical methods, we find that polymerase-helicase attachment promotes multimeric gel-like Polθ complexes that facilitate DNA accumulation, DNA synapsis, and MMEJ. We further find that the central domain regulates Polθ multimerization and governs its DNA substrate requirements for MMEJ. These studies identify unexpected functions for the helicase and central domain and demonstrate the importance of polymerase-helicase tethering in MMEJ and the structural organization of Polθ

Urinary transferrin as an early biomarker of diabetic nephropathy

© 2019 Inst. Sci. inf., Univ. Defence in Belgrade. All rights reserved. Background/Aim: Diabetic nephropathy is one of the leading cause of chronic kidney disease and end-stage renal disease. It occurs in 20%-40% of patients with diabetes mellitus and microal-buminuria is still considered as the first sign of diabetic nephropathy. Low sensitivity and specificity of microalbuminuria lead to more sensitive biomarkers that may be used to detect diabetic nephropathy at an earlier stage with a higher accuracy. This study was carried out to determine whether urinary transferrin can serve as an indicator of diabetic nephropathy. Methods: Our study included 80 type 2 diabetic patients who were classified into two groups: group 1 - normoalbuminuric patients (albumin excretion up to 30 mg/d); group 2 - microalbuminuric patients (albumin excretion from 30-300 mg/d), and 10 healthy controls. All patients were older than 18, having the diabetic disease more than one year, glomerular filtration rate more than 60 mL/min/1.73 m2. Serum creatinine, glycosylated hemoglobin (HbA1c), and concentration of transferrin in the 24 h urine samples as well as in spot urine were measured using a highly sensitive one-step sandwich enzyme immunoassay kit. Results: Urinary transferrin was significantly higher in the microalbuminuric patients than in the normoalbuminuric ones and healthy control subjects. When comparing these goups according to the urinary transferrin concentration, we found a statistically significant positive correlation r = 0.584 (p < 0.001). There was no correlation between level of urinary transferrin and glycoregulation, and no correlation was found between transferrin and duration of diabetes. Conclusions: The results from this study provide the evidence that the urinary transferrin levels could be used as an early marker of diabetic nephropathy

Publisher Correction: Molecular basis of microhomology-mediated end-joining by purified full-length Polθ (Nature Communications, (2019), 10, 1, (4423), 10.1038/s41467-019-12272-9)

The original version of this Article contained errors in Figure 6. In panel o, the labels incorrectly stated ‘Poleθ’ and “Poleθ + DNA” and should be labelled “Polθ” and “Polθ + DNA”. In the result section, in the sub-section entitled “Polθ Promotes MMEJ of Long ssDNA”, the sentence “Importantly, the ability of Polθ- pol to perform MMEJ on short (≤12 nt) ssDNA (Fig. 1p, left; Supplementary Fig. 3D and 3E), and short (≤15 nt) overhangs, demonstrates it performs interstrand pairing without Polθ-hel”. should read as follow: “Importantly, the ability of Polθ-pol to perform MMEJ on short (≤12 nt) ssDNA (Fig. 1p, left; Supplementary Fig. 3D and 3E), and short (≤15 nt) overhangs, demonstrates that it performs interstrand pairing without Polθ-hel”. In the sub-section entitled “Preventing Intrastrand Pairing Stimulates MMEJ by Polθ-Pol”, the sentence “We predicted that preventing base-pairing opportunities between 3' terminal bases and bases upstream along long the 5' region of long ssDNA substrates would suppress intrastrand pairing and enable interstrand pairing by Polθ-pol (Fig. 3c)”. should read as follows: “We predicted that preventing base-pairing opportunities between 3' terminal bases and bases upstream along the 5' region of long ssDNA substrates would suppress intrastrand pairing and enable interstrand pairing by Polθ-pol (Fig. 3c)”. In the method section, in the “Proteins” sub-section the sentence “Polθ-pol, Polθ-hel and RPA were purified as described”. should read as follows: “Polθ-pol and Polθ-hel were purified as described”. These corrections have now been included in the HTML and pdf of the article. Additionally, a technical problem during the publication process resulted in loss of image quality in Figs. 1, 3 and 4. This has now been corrected in both the PDF and HTML versions of the Article