No abstract

RNase III Drosha initiates microRNA (miRNA) maturation by cleaving a primary miRNA transcript and releasing a pre-miRNA with a 2 nt 3' overhang. Dicer recognizes the 2 nt 3' overhang structure to selectively process pre-miRNAs. Here, we find that, unlike prototypic pre-miRNAs (group I), group II pre-miRNAs acquire a shorter (1 nt) 3' overhang from Drosha processing and therefore require a 3'-end mono-uridylation for Dicer processing. The majority of let-7 and miR-105 belong to group II. We identify TUT7/ZCCHC6, TUT4/ZCCHC11, and TUT2/PAPD4/GLD2 as the terminal uridylyl transferases responsible for pre-miRNA mono-uridylation. The TUTs act specifically on dsRNAs with a 1 nt 3' overhang, thereby creating a 2 nt 3' overhang. Depletion of TUTs reduces let-7 levels and disrupts let-7 function. Although the let-7 suppressor, Lin28, induces inhibitory oligo-uridylation in embryonic stem cells, mono-uridylation occurs in somatic cells lacking Lin28 to promote let-7 biogenesis. Our study reveals functional duality of uridylation and introduces TUT7/4/2 as components of the miRNA biogenesis pathway.

Background-A number of distinct stress signaling pathways in myocardium cause cardiac hypertrophy and heart failure.Class II histone deacetylases (HDACs) antagonize several stress-induced pathways and hypertrophy. However, cardiac hypertrophy induced by transgenic overexpression of the homeodomain only protein, HOP, can be prevented by the nonspecific HDAC inhibitors trichostatin A and valproic acid, suggesting that alternate targets that oppose class II HDAC function might exist in myocardium. We tested the effects of several HDAC inhibitors, including a class I HDAC-selective inhibitor, SK-7041, on cardiac hypertrophy induced by angiotensin II (Ang II) treatment or aortic banding (AB). Methods and Results-Cardiac hypertrophy was induced by chronic infusion of Ang II or by AB in mice or rats and evaluated by determining the ratio of heart weight to body weight or to tibia length, cross-sectional area, or echocardiogram. Cardiac hypertrophy induced by Ang II or AB for 2 weeks was significantly reduced by simultaneous administration of trichostatin A, valproic acid, or SK-7041. Echocardiogram revealed that exaggerated left ventricular systolic dimensions were relieved by HDAC inhibitors. HDAC inhibitors partially reversed preestablished cardiac hypertrophy and improved survival of AB mice. The expressions of atrial natriuretic factor, ␣-tubulin, ␤-myosin heavy chain, and interstitial fibrosis were reduced by HDAC inhibition. Conclusions-These results suggest that the predominant effect of HDAC inhibition, mainly mediated by class I HDACs, is to prevent cardiac hypertrophy in response to a broad range of agonist and stretch stimuli.

To evaluate the effects of early combination therapy with intravenous vitamin C and thiamine on recovery from organ failure in patients with septic shock. Methods: The ascorbic acid and thiamine effect in septic shock (ATESS) trial was a multi-centre, double-blind, randomized, controlled trial conducted in four academic emergency departments, enrolling adult patients with septic shock from December 2018 through January 2020. Patients were randomly assigned in a 1:1 ratio to either the treatment group [intravenous vitamin C (50 mg/kg, maximum single dose 3 g) and thiamine (200 mg) administration every 12 h for a total of 48 h] or the placebo group (identical volume of 0.9% saline with the same protocol). The primary outcome was Δ Sequential Organ Failure Assessment (SOFA) score (SOFA score at enrolment-SOFA score after 72 h). Eighteen secondary outcomes were predefined, including shock reversal and 28-day mortality. Results: A total of 111 patients were enrolled, of which 53 were assigned to the treatment group and 58 were assigned to the placebo group. There was no significant difference in ΔSOFA scores between the treatment group and the placebo group [3, interquartile range (IQR) − 1 to 5 vs. 3, IQR 0-4, respectively, p = 0.96]. Predefined secondary outcomes were also not significantly different between the groups. Conclusion: In this study, vitamin C and thiamine administration in the early phase of septic shock did not improve organ function compared with placebo, despite improvements in vitamin C and thiamine levels.