Der humane Replikationsfaktor Cdc45: Lokalisation und Interaktionspartner

Cdc45 (cell division cycle protein 45) ist ein essentieller Replikationsfaktor, der in der Initiation und Elongation der DNA-Replikation beteiligt ist. Ziel dieser Arbeit war es, die Lokalisation und mögliche Interaktionspartner von humanem Cdc45 mittels biochemischer und zellbiologischer Techniken zu charakterisieren. Endogenes Cdc45 wurde von der späten G1-Phase bis zur G2-Phase im Zellkern vorgefunden und zeigte eine Co-Lokalisation mit aktiven Replikationsstellen speziell in der S-Phase. Es wurde erstmals gezeigt, dass humanes Cdc45-Protein in räumlicher Nähe der Proteine Mcm7, DNA-Polymerase alpha und DNA-Polymerase epsilon in frühen S-Phase-Zellen zu beobachten war. Weiterhin, aber nur in bestimmten Zellbereichen, konnte eine Co-Lokalisation von RPA mit Cdc45 gefunden werden

Cohesin promotes the repair of ionizing radiation-induced DNA double-strand breaks in replicated chromatin

The cohesin protein complex holds sister chromatids together after synthesis until mitosis. It also contributes to post-replicative DNA repair in yeast and higher eukaryotes and accumulates at sites of laser-induced damage in human cells. Our goal was to determine whether the cohesin subunits SMC1 and Rad21 contribute to DNA double-strand break repair in X-irradiated human cells in the G2 phase of the cell cycle. RNA interference-mediated depletion of SMC1 sensitized HeLa cells to X-rays. Repair of radiation-induced DNA double-strand breaks, measured by γH2AX/53BP1 foci analysis, was slower in SMC1- or Rad21-depleted cells than in controls in G2 but not in G1. Inhibition of the DNA damage kinase DNA-PK, but not ATM, further inhibited foci loss in cohesin-depleted cells in G2. SMC1 depletion had no effect on DNA single-strand break repair in either G1 or late S/G2. Rad21 and SMC1 were recruited to sites of X-ray-induced DNA damage in G2-phase cells, but not in G1, and only when DNA damage was concentrated in subnuclear stripes, generated by partially shielded ultrasoft X-rays. Our results suggest that the cohesin complex contributes to cell survival by promoting the repair of radiation-induced DNA double-strand breaks in G2-phase cells in an ATM-dependent pathway

Cohesin phosphorylation and mobility of SMC1 at ionizing radiation-induced DNA double-strand breaks in human cells

Cohesin, a hetero-tetrameric complex of SMC1, SMC3, Rad21 and Scc3, associates with chromatin after mitosis and holds sister chromatids together following DNA replication. Following DNA damage, cohesin accumulates at and promotes the repair of DNA double-strand breaks. In addition, phosphorylation of the SMC1/3 subunits contributes to DNA damage-induced cell cycle checkpoint regulation. The aim of this study was to determine the regulation and consequences of SMC1/3 phosphorylation as part of the cohesin complex. We show here that the ATM-dependent phosphorylation of SMC1 and SMC3 is mediated by H2AX, 53BP1 and MDC1. Depletion of RAD21 abolishes these phosphorylations, indicating that only the fully assembled complex is phosphorylated. Comparison of wild type SMC1 and SMC1S966A in fluorescence recovery after photo-bleaching experiments shows that phosphorylation of SMC1 is required for an increased mobility after DNA damage in G2-phase cells, suggesting that ATM-dependent phosphorylation facilitates mobilization of the cohesin complex after DNA damage

Incidence and Risk Factors for Acute Transient Contrast‐Induced Neurologic Deficit: A Systematic Review With Meta‐Analysis

Background After MR CLEAN (Multicenter Randomized Clinical Trial of Endovascular Treatment for Acute Ischemic Stroke in the Netherlands) demonstrated that endovascular therapy improved outcomes in patients with stroke, the number of endovascular procedures has risen sharply. We describe acute transient contrast‐induced neurological deficit (ATCIND), a group of neurological syndromes associated with arterial contrast administration during angiography. Our goal is to elucidate the incidence, risk factors, outcomes, pathogenesis, and diagnostic characteristics of ATCIND. Our primary objective is to elucidate the incidence of ATCIND in the setting of coronary or cerebral angiography. Secondary outcomes include potential risk factors, demographics, treatment modalities, and patient recovery. Methods The data that support the findings of this study are available from the corresponding author on reasonable request. The databases of the Cochrane Library, MEDLINE, Web of Science, and Embase were queried, yielding studies from 1974 to 2021. Inclusion criteria for articles were the following: (1) contrast‐induced encephalopathy, contrast‐induced neurotoxicity, or cortical blindness after contrast administration during angiography were the focus of the article; (2) incidence was reported; (3) studies included ≥3 cases; and (4) follow‐up tests were described to rule out other causes. Exclusion criteria included the following: (1) incidence was not reported; (2) unavailable in the English language; (3) abstracts and unpublished studies; and (4) did not exclude other possible causes, or findings suggested other possible causes, such as worsening ischemic injury. Of 627 articles, 7 were retained. This systematic review with meta‐analysis was performed in accordance with guidelines provided by the Preferred Reporting Items for Systematic Reviews and Meta‐Analyses (PRISMA) and the Meta‐Analysis of Observational Studies in Epidemiology (MOOSE) checklists. Independent extraction by multiple reviewers was performed. Data were pooled using a random‐effects model. Results The primary study outcome was incidence of ATCIND, which was formulated before data collection began. We hypothesized that the pooled incidence of ATCIND would be similar to that of individual studies. A total of 70 of 21007 patients had the diagnosis of contrast‐induced encephalopathy, contrast‐induced neurotoxicity or angiography‐associated cortical blindness, and ATCIND. The incidence rate of ATCIND is estimated to be 0.51% (CI, 0.3%–1.0%; P150 mL was a positive, significant predictor of visual disturbance (OR, 7.083; CI, 1.1742–42.793 [P=0.033]). Full recovery is estimated at 89.5% (95% CI, 76.9%–95.6%; P<0.001 [I2=0]). Conclusions This study confirms the rare incidence of ATCIND, although it shows moderate heterogeneity, likely reflecting the type of angiography performed. Risk factors include larger contrast dose and prior stroke. Full recovery occurs in the majority of patients. It should remain in the differential diagnosis in patients with certain risk factors for blood–brain barrier compromise

Utility of Frailty as a Predictor of Acute Kidney Injury in Patients With Aneurysmal Subarachnoid Hemorrhage

INTRODUCTION: Acute kidney injury (AKI) is associated with poor outcome in aneurysmal subarachnoid hemorrhage patients (aSAH). Frailty has recently been demonstrated to correlate with elevated mortality and morbidity; its impact on predicting AKI and mortality in aSAH patients has not been investigated. OBJECTIVE: Evaluating risk factors and predictors for AKI in aSAH patients. METHODS: aSAH patients from a single-center\u27s prospectively maintained database were retrospectively evaluated for development of AKI within 14 days of admission. Baseline demographic and clinical characteristics were collected. The effect of frailty and other risk factors were evaluated. RESULTS: Of 213 aSAH patients, 53 (33.1%) were frail and 12 (5.6%) developed AKI. Admission serum creatinine (sCr) and peak sCr within 48 h were higher in frail patients. AKI patients showed a trend towards higher frailty. Mortality was significantly higher in AKI than non-AKI aSAH patients. Frailty was a poor predictor of AKI when controlling for Hunt and Hess (HH) grade or age. HH grade ≥ 4 strongly predicted AKI when controlling for frailty. CONCLUSION: AKI in aSAH patients carries a poor prognosis. The HH grade appears to have superior utility as a predictor of AKI in aSAH patients than mFI