Binding of the RNA Chaperone Hfq on Target mRNAs Promotes the Small RNA RyhB-Induced Degradation in Escherichia coli.

Many RNA-RNA interactions depend on molecular chaperones to form and remain stable in living cells. A prime example is the RNA chaperone Hfq, which is a critical effector involved in regulatory interactions between small RNAs (sRNAs) and cognate target mRNAs in Enterobacteriaceae. While there is a great deal of in vitro biochemical evidence supporting the model that Hfq enhances rates or affinities of sRNA:mRNA interactions, there is little corroborating in vivo evidence. Here we used in vivo tools including reporter genes, co-purification assays, and super-resolution microscopy to analyze the role of Hfq in RyhB-mediated regulation, and we found that Hfq is often unnecessary for efficient RyhB:mRNA complex formation in vivo. Remarkably, our data suggest that a primary function of Hfq is to promote RyhB-induced cleavage of mRNA targets by RNase E. Moreover, our work indicates that Hfq plays a more limited role in dictating regulatory outcomes following sRNAs RybB and DsrA complex formation with specific target mRNAs. Our investigation helps evaluate the roles played by Hfq in some RNA-mediated regulation.

Prediction and impact of failure of transradial approach for primary percutaneous coronary intervention.

OBJECTIVES: To determine predictors of failure of transradial approach (TRA) in patients with ST elevation myocardial infarction (STEMI) undergoing primary percutaneous coronary intervention (PCI), and develop a novel score specific for this population. METHODS: Consecutive patients with STEMI undergoing primary PCI in a tertiary care high-volume radial centre were included. TRA-PCI failure was categorised as primary (primary transfemoral approach (TFA)) or crossover (from TRA to TFA). Multivariate analysis was performed to determine independent predictors of TRA-PCI failure, and an integer risk score was developed. Clinical outcomes up to 1 year were assessed. RESULTS: From January 2006 to January 2011, 2020 patients were studied. Primary TRA-PCI failure occurred in 111 (5%) patients and crossover to TFA in 44 (2.2%) patients. Independent predictors of TRA-PCI failure were: weight ≤65 kg (OR: 3.0; 95% CI 1.9 to 4.8, p<0.0001), physician with ≤5% TFA conversion (OR: 0.45; 95% CI 0.2 to 0.9, p=0.033), and physician with ≥10% conversion to TFA (OR: 2.2; 95% CI 1.2 to 3.7, p=0.005), intra-aortic balloon pump (OR: 2.0; 95% CI 0.9 to 4.3, p=0.066), cardiogenic shock (OR: 2.8; 95% CI 1.4 to 5.6, p=0.0035), endotracheal intubation (OR: 107; 95% CI 42 to 339, p<0.0001), creatinine >133 µmol/L (OR: 3.6; 95% CI 1.9 to 6.8, p<0.0001), age ≥75 (OR: 1.7; 95% CI 1.0 to 2.9, p=0.031), prior PCI (OR: 2.6; 95% CI 1.5 to 4.5, p=0.0009), hypertension (OR: 1.8; 95% CI 1.2 to 2.9, p=0.009). An integer risk score ranging from -1 to 12 was developed, and predicted TRA-PCI failure from 0% to 100% (c-statistic of 0.868; 95% CI 0.866 to 0.869). Mortality at 1 year remained significantly higher after TRA-PCI failure (adjusted OR 2.2; 95% CI 1.2 to 3.9, p=0.011). CONCLUSIONS: In a high-volume radial centre, the incidence of TRA-PCI failure is low and can be accurately predicted using a 9-variables risk score. Since outcomes after TRA-PCI failure remained inferior, further effort to maximise the use of radial approach for primary PCI should be investigated.

New insights into small RNA-dependent translational regulation in prokaryotes.

Bacterial small RNAs (sRNAs) typically repress translation of target mRNAs by pairing directly to the ribosome-binding site (RBS) and competing with initiating ribosomes, an event that is often followed by rapid mRNA decay. In recent years, however, many examples of translation-repressing sRNAs pairing outside the RBS have been described. In this review, we focus on newly characterized mechanisms that explain how a sRNA can modulate translation by binding outside of the RBS and discuss new insights into the events following translation repression. These new mechanisms broaden current perspectives of sRNA pairing sites on mRNA targets and demonstrate how the interplay between sRNAs, mRNA structures, and protein partners can contribute to post-transcriptional regulation.