Slx5/Slx8-dependent ubiquitin hotspots on chromatin contribute to stress tolerance.

Chromatin is a highly regulated environment, and protein association with chromatin is often controlled by post-translational modifications and the corresponding enzymatic machinery. Specifically, SUMO-targeted ubiquitin ligases (STUbLs) have emerged as key players in nuclear quality control, genome maintenance, and transcription. However, how STUbLs select specific substrates among myriads of SUMOylated proteins on chromatin remains unclear. Here, we reveal a remarkable co-localization of the budding yeast STUbL Slx5/Slx8 and ubiquitin at seven genomic loci that we term "ubiquitin hotspots". Ubiquitylation at these sites depends on Slx5/Slx8 and protein turnover on the Cdc48 segregase. We identify the transcription factor-like Ymr111c/Euc1 to associate with these sites and to be a critical determinant of ubiquitylation. Euc1 specifically targets Slx5/Slx8 to ubiquitin hotspots via bipartite binding of Slx5 that involves the Slx5 SUMO-interacting motifs and an additional, novel substrate recognition domain. Interestingly, the Euc1-ubiquitin hotspot pathway acts redundantly with chromatin modifiers of the H2A.Z and Rpd3L pathways in specific stress responses. Thus, our data suggest that STUbL-dependent ubiquitin hotspots shape chromatin during stress adaptation.

Endovascular Repair of Penetrating Thoracic Aortic Ulcers Using Tubular Stent Grafts Versus Stent Grafts With a Proximal Scallop.

PURPOSE: In penetrating aortic ulcers (PAUs), limited data support tubular thoracic endovascular aortic repair (TEVAR) as a viable treatment option. For treatment of more proximal PAUs, hybrid approaches and-more recently-scalloped TEVAR (scTEVAR) have been advocated. Outcomes of scTEVAR specifically for PAUs have not yet been reported. This study reports long-term outcomes for tubular and scTEVAR in PAUs and compares the safety profile in both cohorts regarding the significantly more proximal landing zone (LZ) for scTEVAR. MATERIALS AND METHODS: This single-center retrospective cohort study includes all nonacute patients treated for complicated PAU with scTEVAR and tubular TEVAR. Patient and PAU characteristics as well as procedural success, complication and reintervention rates, and all-cause and aortic mortality were analyzed. RESULTS: Of 212 TEVAR procedures reviewed, 21 patients with tubular TEVAR and 19 patients with scTEVAR were included. Patient and PAU characteristics were similar, and LZ was significantly more proximal in the scTEVAR cohort (p=0.0001), with similar number and types of supra-aortic revascularization procedures. Clinical success was reached in all 40 patients (100%), and reintervention rate was 2/21 (9.5%) and 1/19 (5.3%), respectively. Over the mean follow-up of 63 (TEVAR) and 53 (scTEVAR) months, clinical success was stable in all patients with one (abdominal) aortic-related mortality in the scTEVAR cohort. CONCLUSION: Treatment of complicated PAUs with TEVAR as well as scTEVAR provides excellent and similar clinical success, stability of clinical success, and aortic survival with acceptable complication and reintervention rates. Scalloped TEVAR safely lengthens the proximal sealing zone to address more proximal pathologies. CLINICAL IMPACT: Treatment of asymptomatic complicated penetrating aortic ulcers (PAUs) with thoracic endovascular aortic repair (TEVAR) provides excellent clinical success and acceptable complication and reintervention rates. More patients become amenable to endovascular treatment by including scalloped TEVAR (scTEVAR) as a means to safely lengthen the proximal sealing zone to address more proximal pathologies.

Applicability of endovascular branched and fenestrated aortic arch repair devices to treat residual type A dissection after ascending replacement.

OBJECTIVE: Endovascular repair of post-type A aortic dissection (PTAD) after open ascending replacement has recently been shown as safe and feasible, but with limited anatomic applicability because only one stent graft was evaluated. We assessed anatomic and clinical applicability of six commercially available branched/fenestrated stent grafts for endovascular repair of PTAD. METHODS: On postoperative CT scans of 101 patients, we measured the aortic diameter at the sinutubular junction, supra-aortic vessels, and descending aorta, as well as the distances between these landmarks along the outer curvature of the arch and the diameters of the supra-aortic vessel. Anatomic applicability was evaluated according to the instructions for use, clinical applicability with regard to supra-aortic and iliac arteries. Assessed devices were the Cook aortic double branch, Terumo double branch, Najuta fenestrated, Endospan Nexus, Medtronic Mona LSA, and Gore TAG thoracic branch. RESULTS: Single devices were anatomically and clinically applicable between 19 of 101 (Mona LSA) and 83 of 101 (Najuta) cases. Reasons for rejection varied considerably across devices. With all devices available, anatomic applicability was 97 of 101 and clinical applicability 95 of 101. Combinations of a fenestrated and a branched device showed the most favorable clinical applicability for a pair of two devices, ranging from 86 of 101 to 94 of 101. CONCLUSIONS: Anatomic and clinical applicability of endovascular devices for the repair of PTAD is high for fenestrated and branched devices, and very high for the combination of fenestrated and branched devices. Manufacturers should amend specific device requirements for PTAD. Surgeons should emphasize the need for a sufficiently long and straight graft as a potential landing zone.

Optimizing protein stability in vivo.

Identifying mutations that stabilize proteins is challenging because most substitutions are destabilizing. In addition to being of immense practical utility, the ability to evolve protein stability in vivo may indicate how evolution has formed today's protein sequences. Here we describe a genetic selection that directly links the in vivo stability of proteins to antibiotic resistance. It allows the identification of stabilizing mutations within proteins. The large majority of mutants selected for improved antibiotic resistance are stabilized both thermodynamically and kinetically, indicating that similar principles govern stability in vivo and in vitro. The approach requires no prior structural or functional knowledge and allows selection for stability without a need to maintain function. Mutations that enhance thermodynamic stability of the protein Im7 map overwhelmingly to surface residues involved in binding to colicin E7, showing how the evolutionary pressures that drive Im7-E7 complex formation have compromised the stability of the isolated Im7 protein.

Preliminary results of the Austrian National Registry regarding the novel iCover bridging stent graft in fenestrated endovascular aortic repair.

OBJECTIVE: Bridging stentgrafts (BSGs) are one of the primary limiting factors regarding long-term results after fenestrated endovascular aortic repair (fEVAR). This study aims to report for the first time the outcome of a novel BSG called iCover from a national, multicentric retrospective database. METHODS: A cohort of 58 patients received 212 BSGs for the renovisceral arteries in fEVAR. Patients were followed-up clinically and with computed-tomography angiography. Study end points were mortality, occurrence of complications, technical success of the BSG implantation, defined as successful deployment with vessel patency and absence of type 1c, 3b, and 3c endoleak, and stability over the follow-up. RESULTS: Three BSG unrelated mortalities (5.1 %), four BSG unrelated major complications (6.8 %) and five minor complications (8.6 %) occurred. The technical success of iCover was 207/212 (97.6 %), target vessel patency was 100 % over a follow-up of 4.0 months, and no late BSG related endoleak was detected. In two cases, the BSG was dislodged from the balloon and could be parked in a safe position without further sequelae (0.9 %). CONCLUSION: The iCover represents a feasible BSG for fEVAR with an excellent safety profile and technical success rate in the early phase. Prudent post-dilatation and monitoring of the proximal and distal stent ends can potentially further improve outcome. Longer follow-up series are necessary.

Endovascular repair in type A aortic dissection: Anatomical candidacy for currently manufactured stent grafts and conceptual valve-carrying devices for an Endo-Bentall procedure.

OBJECTIVES: Endovascular treatment has been suggested as an alternative for open surgery for type A aortic dissection, but current devices have severe anatomical limitations. This study assesses the computed tomography-based anatomical suitability of currently manufactured stent grafts as well as 2 embodiments of valve-carrying devices. METHODS: In a retrospective single-centre cohort of 200 consecutive ascending/arch operations between 2009 and 2018, a total of 112 patients with type A aortic dissections were identified and evaluated for endovascular candidacy based on the locations of the entries, the landing zone diameters/lengths and the supra-aortic vessel origins according to the anatomical instructions for use criteria of 6 commercially available (tubular, branched or fenestrated) stent grafts. Two suggested valve-carrying devices with inner branches or fenestrations for the coronary arteries and branches for the supra-aortic vessels were also evaluated. RESULTS: The anatomical feasibility for commercial stent grafts ranged from 4% to 21%. The main limitations were proximal landing zone diameter (considering oversizing <15%), length due to dilatation and an entry too close to the sinotubular junction. For the valve-carrying conduits, anatomical feasibility was between 31% and 80%, with the main limiting factors being the diameter of the aortic annulus and its distance to the coronary arteries. CONCLUSIONS: The anatomical applicability of currently manufactured stent grafts for the treatment of type A aortic dissection is limited mainly by the absence of a suitable proximal landing zone in the ascending aorta and might substantially be improved by anchoring in the aortic annulus using a valve-carrying device that uses either fenestrations or branches for the coronary arteries.

The FAM104 proteins VCF1/2 promote the nuclear localization of p97/VCP.

The ATPase p97 (also known as VCP, Cdc48) has crucial functions in a variety of important cellular processes such as protein quality control, organellar homeostasis, and DNA damage repair, and its de-regulation is linked to neuromuscular diseases and cancer. p97 is tightly controlled by numerous regulatory cofactors, but the full range and function of the p97-cofactor network is unknown. Here, we identify the hitherto uncharacterized FAM104 proteins as a conserved family of p97 interactors. The two human family members VCP nuclear cofactor family member 1 and 2 (VCF1/2) bind p97 directly via a novel, alpha-helical motif and associate with p97-UFD1-NPL4 and p97-UBXN2B complexes in cells. VCF1/2 localize to the nucleus and promote the nuclear import of p97. Loss of VCF1/2 results in reduced nuclear p97 levels, slow growth, and hypersensitivity to chemical inhibition of p97 in the absence and presence of DNA damage, suggesting that FAM104 proteins are critical regulators of nuclear p97 functions.

[Endovascular aortic repair of endoleaks : Diagnosis, treatment, and outcomes]. / Endovaskuläre Aortenreparatur bei Endoleaks : Diagnose, Behandlung und Ergebnisse.

All patients who underwent endovascular aortic repair (EVAR) need a thorough follow-up, at least yearly. Contrast-enhanced ultrasound and computed tomography angiography (CTA) are the most important modalities for detection of endoleaks, whereby CTA allows better differentiation of endoleak type. High pressure endoleaks (type I and III) are an absolute indication for treatment if they do not resolve spontaneously in the short term. Type II endoleaks are mostly benign and may be routinely controlled if there is no progression of the aneurysm. Type II endoleaks associated with aneurysm progression may be treated with embolization; however, whether they must be treated is a matter of discussion. Nonetheless, a type II endoleak must be treated when progression shortens the aneurysm neck and the threat of a type I endoleak is at hand. Type I endoleaks are the main limitation of stent grafts. An adequate proximal landing zone is the best prevention for type I endoleaks, even if fenestrated stent grafts have to be used. Various fixation devices for short necks are currently under investigation.

[Fenestrated and branched endovascular aortic prostheses : An update]. / Fenestrierte und verzweigte endovaskuläre Aortenprothesen : Ein Update.

BACKGROUND: Today, complex abdominal aortic pathologies involving the visceral arteries and without an adequate proximal neck can be treated using fenestrated/branched endovascular aortic repair (FEVAR/BEVAR) with similar safety and success rates as infrarenal aortic pathologies treated with tubular EVAR. METHODICAL INNOVATIONS AND CHALLENGES: Fenestrations (if the vessel originates from a nondilated aorta) or branches (if the vessel originates from a dilated aorta) may be used for the visceral arteries. Both types of openings are sealed via bridging stent grafts that connect to the target vessel. Multiple manufacturers offer fenestrated or branched endoprostheses, with only a few being CE certified and the majority in Europe being patient-specific custom-made devices. Therefore, they require a certain delivery time which precludes acute patients from such treatment. However, two stent grafts with four branches for thoracoabdominal aneurysms are available off the shelf and are anatomically suitable for the majority of patients, thus, allowing for acute treatment. All FEVAR and BEVAR main bodies require bridging stent grafts, all of which are used off-label. RECOMMENDATIONS: As bridging stent grafts are one of the main reasons for reinterventions, one should be aware of fractures and kinking of the bridging stent grafts during follow-up and should refrain from using single-layered bridging stent grafts in BEVAR.

Use of a Steerable Sheath for Completely Femoral Access in Branched Endovascular Aortic Repair Compared to Upper Extremity Access.

PURPOSE: To compare bridging stent graft (BSG) implantation in downward oriented branches in branched endovascular aortic repair (bEVAR), using a commercially available steerable sheath from an exclusively femoral access (TFA) with traditional upper extremity access (UEA). METHODS: In a retrospective cohort study, 7 patients with 19 branches in the TFA cohort received BSG insertion using the Medtronic Heli FX steerable sheath from a femoral access, and 10 patients with 32 branches in the UEA cohort from a brachial approach. Technical success, total intervention time, fluoroscopy time, branch cannulation time, and complication rate were recorded. RESULTS: Technical success was 19/19 branches in the TFA and 31/32 in the UEA cohort. The mean branch cannulation time was considerably shorter in the TFA group (17 vs. 29 min, p = 0.003), and total intervention time tended to be shorter (169 vs. 217 min, p = 0.176). CONCLUSION: Using a commercially available steerable sheath allowed successful cannulation of all branches in this cohort and was associated with significantly shorter branch cannulation times. Potentially, this technique can lower the stroke and brachial puncture site complication risk as well as reduce total intervention time and radiation dose. LEVEL OF EVIDENCE: 2b, retrospective cohort study.

Branched versus fenestrated thoracic endovascular aortic repair in the aortic arch: A multicenter comparison.

OBJECTIVE: For thoracic endovascular aortic repair of the arch, branched and fenestrated endografts are available with different limitations regarding anatomy and extent of the pathology. Comparisons are lacking in the literature. The aim of this study was to compare the results of 2 currently commercially available devices for branched thoracic endovascular aortic repair and fenestrated thoracic endovascular aortic repair. METHODS: In a retrospective, multicenter cohort study, a consecutive patient series treated with branched thoracic endovascular aortic repair or fenestrated thoracic endovascular aortic repair for aortic arch pathologies was assessed. Baseline characteristics, procedural fenestrated thoracic endovascular aortic repair, and outcome were analyzed. Furthermore, the potential anatomic feasibility of the respective alternate device was assessed on the preoperative computed tomography scans. RESULTS: The branched thoracic endovascular aortic repair and fenestrated thoracic endovascular aortic repair cohorts consisted of 20 and 34 patients, respectively, with similar comorbidities; indication was aneurysm in 65% and 79%, penetrating aortic ulcer in 20% and 9%, and dissection in the remaining procedures, respectively. Technical success was achieved in all but 1 patient. Perioperative mortality and major stroke rate were both 10% in branched thoracic endovascular aortic repair and 0% and 3% in fenestrated thoracic endovascular aortic repair, respectively. During follow-up of 31 and 40 months, 1 branch occlusion occurred in the branched thoracic endovascular aortic repair cohort, and 2 late endoleaks occurred in the fenestrated thoracic endovascular aortic repair group. One aortic death occurred. Although 35% of patients undergoing branched thoracic endovascular aortic repair were anatomically suitable for fenestrated thoracic endovascular aortic repair, 91% of those undergoing fenestrated thoracic endovascular aortic repair were suitable for branched thoracic endovascular aortic repair. CONCLUSIONS: Both branched thoracic endovascular aortic repair and fenestrated thoracic endovascular aortic repair show excellent technical success and acceptable complication rates, whereas branched thoracic endovascular aortic repair tends toward higher morbidity, especially stroke rates. By offering fenestrated thoracic endovascular aortic repair along with branched thoracic endovascular aortic repair, aortic centers could potentially lower complication rates and simultaneously still treat a wide range of anatomies.

UBXD1 binds p97 through two independent binding sites.

The chaperone-related p97 protein plays a central role in various cellular processes involving the ubiquitin-proteasome system. The diverse functions of p97 are controlled by a large number of cofactors that recruit specific substrates or influence their ubiquitylation state. Many cofactors bind through a UBX or PUB domain, two major p97 binding modules. However, the recently identified UBXD1 cofactor possesses both domains. To elucidate the molecular basis underlying the interaction between UBXD1 and p97, we analyzed the contribution of both domains to p97 binding biochemically and in living cells. The PUB domain mediated robust binding to the carboxy-terminus of p97, while the UBX domain did not contribute to p97 binding. Importantly, we identified an additional p97 binding site in UBXD1 that competed with the p47 cofactor for binding to the N domain of p97. This novel, bipartite binding mode suggests that UBXD1 could be an efficient regulator of p97 cofactor interactions.

A SUMO-dependent pathway controls elongating RNA Polymerase II upon UV-induced damage.

RNA polymerase II (RNAPII) is the workhorse of eukaryotic transcription and produces messenger RNAs and small nuclear RNAs. Stalling of RNAPII caused by transcription obstacles such as DNA damage threatens functional gene expression and is linked to transcription-coupled DNA repair. To restore transcription, persistently stalled RNAPII can be disassembled and removed from chromatin. This process involves several ubiquitin ligases that have been implicated in RNAPII ubiquitylation and proteasomal degradation. Transcription by RNAPII is heavily controlled by phosphorylation of the C-terminal domain of its largest subunit Rpb1. Here, we show that the elongating form of Rpb1, marked by S2 phosphorylation, is specifically controlled upon UV-induced DNA damage. Regulation of S2-phosphorylated Rpb1 is mediated by SUMOylation, the SUMO-targeted ubiquitin ligase Slx5-Slx8, the Cdc48 segregase as well as the proteasome. Our data suggest an RNAPII control pathway with striking parallels to known disassembly mechanisms acting on defective RNA polymerase III.

Role of Cdc48/p97 as a SUMO-targeted segregase curbing Rad51-Rad52 interaction.

Cdc48 (also known as p97), a conserved chaperone-like ATPase, plays a strategic role in the ubiquitin system. Empowered by ATP-driven conformational changes, Cdc48 acts as a segregase by dislodging ubiquitylated proteins from their environment. Ufd1, a known co-factor of Cdc48, also binds SUMO (ref. 6), but whether SUMOylated proteins are subject to the segregase activity of Cdc48 as well and what these substrates are remains unknown. Here we show that Cdc48 with its co-factor Ufd1 is SUMO-targeted to proteins involved in DNA double-strand break repair. Cdc48 associates with SUMOylated Rad52, a factor that assembles the Rad51 recombinase on chromatin. By acting on the Rad52-Rad51 complex, Cdc48 curbs their physical interaction and displaces the proteins from DNA. Genetically interfering with SUMO-targeting or segregase activity leads to an increase in spontaneous recombination rates, accompanied by aberrant in vivo Rad51 foci formation in yeast and mammalian cells. Our data thus suggest that SUMO-targeted Cdc48 restricts the recombinase Rad51 by counterbalancing the activity of Rad52. We propose that Cdc48, through its ability to associate with co-factors that have affinities for ubiquitin and SUMO, connects the two modification pathways for protein degradation or other regulatory purposes.