Ubiquitin-induced RNF168 condensation promotes DNA double-strand break repair.

Rapid accumulation of repair factors at DNA double-strand breaks (DSBs) is essential for DSB repair. Several factors involved in DSB repair have been found undergoing liquid-liquid phase separation (LLPS) at DSB sites to facilitate DNA repair. RNF168, a RING-type E3 ubiquitin ligase, catalyzes H2A.X ubiquitination for recruiting DNA repair factors. Yet, whether RNF168 undergoes LLPS at DSB sites remains unclear. Here, we identified K63-linked polyubiquitin-triggered RNF168 condensation which further promoted RNF168-mediated DSB repair. RNF168 formed liquid-like condensates upon irradiation in the nucleus while purified RNF168 protein also condensed in vitro. An intrinsically disordered region containing amino acids 460-550 was identified as the essential domain for RNF168 condensation. Interestingly, LLPS of RNF168 was significantly enhanced by K63-linked polyubiquitin chains, and LLPS largely enhanced the RNF168-mediated H2A.X ubiquitination, suggesting a positive feedback loop to facilitate RNF168 rapid accumulation and its catalytic activity. Functionally, LLPS deficiency of RNF168 resulted in delayed recruitment of 53BP1 and BRCA1 and subsequent impairment in DSB repair. Taken together, our finding demonstrates the pivotal effect of LLPS in RNF168-mediated DSB repair.

RAP80 phase separation at DNA double-strand break promotes BRCA1 recruitment.

RAP80 has been characterized as a component of the BRCA1-A complex and is responsible for the recruitment of BRCA1 to DNA double-strand breaks (DSBs). However, we and others found that the recruitment of RAP80 and BRCA1 were not absolutely temporally synchronized, indicating that other mechanisms, apart from physical interaction, might be implicated. Recently, liquid-liquid phase separation (LLPS) has been characterized as a novel mechanism for the organization of key signaling molecules to drive their particular cellular functions. Here, we characterized that RAP80 LLPS at DSB was required for RAP80-mediated BRCA1 recruitment. Both cellular and in vitro experiments showed that RAP80 phase separated at DSB, which was ascribed to a highly disordered region (IDR) at its N-terminal. Meanwhile, the Lys63-linked poly-ubiquitin chains that quickly formed after DSBs occur, strongly enhanced RAP80 phase separation and were responsible for the induction of RAP80 condensation at the DSB site. Most importantly, abolishing the condensation of RAP80 significantly suppressed the formation of BRCA1 foci, encovering a pivotal role of RAP80 condensates in BRCA1 recruitment and radiosensitivity. Together, our study disclosed a new mechanism underlying RAP80-mediated BRCA1 recruitment, which provided new insight into the role of phase separation in DSB repair.

Low-density lipoprotein cholesterol in oldest old with acute myocardial infarction: Is lower the better?

BACKGROUND: the relationship between low-density lipoprotein cholesterol (LDL-C) and adverse outcomes among the older people remains controversial. OBJECTIVE: to further clarify the association between admission LDL-C levels and cardiovascular mortality (CVM) among oldest old individuals (≥80 years) with acute myocardial infarction (AMI). DESIGN: a prospective cohort study. SETTING: two-centre. SUBJECTS: a consecutive sample of 1,224 oldest old individuals with AMI admitted to Beijing FuWai and Shenzhen FuWai hospitals. METHODS: all individuals were subdivided according to baseline LDL-C levels (<1.8, 1.8-2.6 and ≥ 2.6 mmol/l) and further stratified by high-sensitivity C-reactive protein (hsCRP) concentrations (<10 and ≥10 mg/l). The primary outcome was CVM. The time from admission to the occurrence of CVM or the last follow-up was analysed in Kaplan-Meier and Cox analyses. RESULTS: the median age of the overall population was 82 years. During an average of 24.5 months' follow-up, 299 cardiovascular deaths occurred. Kaplan-Meier analysis showed that LDL-C < 1.8 mmol/l group had the highest CVM among oldest old individuals with AMI. Multivariate Cox regression analysis further revealed that compared with those with LDL-C levels <1.8 mmol/l, subjects with LDL-C levels ≥2.6 mmol/l (hazard ratio: 0.67, 95% confidence interval: 0.46-0.98) had significantly lower risk of CVM, especially in those with high hsCRP levels. Moreover, when categorising according to LDL-C and hsCRP together, data showed that individuals with low LDL-C and high hsCRP levels had the highest CVM. CONCLUSIONS: LDL-C < 1.8 mmol/l was associated with a high CVM after AMI in oldest old individuals, especially when combined with high hsCRP levels, which may need to be confirmed by randomised controlled trials.

Prognostic impacts of ß-blockers in acute coronary syndrome patients without heart failure treated by percutaneous coronary intervention.

BACKGROUND: The use of ß-blockers for acute coronary syndrome (ACS) patients without heart failure (HF) is controversial, and lacks of evidence in the era of reperfusion and intensive secondary preventions. This study aimed to investigate the prognostic impacts of ß-blockers on patients with ACS but no HF treated by percutaneous coronary intervention (PCI). METHODS: A total of 2397 consecutive patients with ACS but no HF treated by PCI were retrospectively recruited from January 2010 to June 2017. Univariable Cox regression was used to assess the prognostic impacts of ß-blockers, followed by adjusted analysis, one-to-one propensity score matching (PSM), and inverse probability treatment weighting (IPTW) analysis, in order to control for systemic between-group differences. The primary outcome was all-cause death. RESULTS: Among the included patients, 2060 (85.9%) were prescribed with ß-blockers at discharge. The median follow-up time was 727 (433-2016) days, with 55 (2.3%) cases of all-cause death. Unadjusted analysis showed that the use of ß-blockers was associated with lower risk of death (hazard ratio [HR]: 0.42, 95% confidence interval [CI]: 0.23-0.76, P = 0.004), which was sustained in adjusted analysis (HR: 0.53, 95% CI: 0.29-0.98, P = 0.044), PSM analysis (HR: 0.44, 95% CI: 0.20-0.96, P = 0.039) and IPTW analysis (HR: 0.49. 95% CI: 0.35-0.70, P < 0.001). Risk reduction was also seen in ß-blocker users for cardiac death, but not for major adverse cardiovascular events. CONCLUSIONS: The use of ß-blockers was associated with reduced long-term mortality for ACS-PCI patients without HF.

Mean Platelet Volume/Platelet Count Ratio and Culprit Plaque Morphologies: An Optical Coherence Tomography Study in Patients with ST Segment Elevation Myocardial Infarction.

This study aimed to investigate the predictive value of mean platelet volume/platelet count ratio (MPR) for coronary plaque features in patients with ST segment elevation myocardial infarction (STEMI). A total of 275 STEMI patients undergoing preintervention optical coherence tomography examination were included, with 142 categorized as plaque rupture (PR) and 133 as plaque erosion (PE). Multivariable logistic regression showed higher MPR was an independent predictor of PR (tertile 3 vs tertile 1, odds ratio: 6.257, 95% confidence interval: 1.586-24.686, P = 0.009). MPR showed better diagnostic performance than other platelet indices. The optimal MPR threshold for diagnosing PR was 0.0473 (sensitivity: 0.721, specificity: 0.647). When added to models of established risk factors, MPR significantly improved the predictive accuracy of PR (area under the curve: 0.767 vs 0.722, P difference = 0.004). In conclusion, for STEMI patients, MPR was an independent predictor of PR and improved diagnostic performance for PR.