Search

This study aims to analyze survival, repeat hospitalization, and risk factors for surgically treated left-sided endocarditis. Retrospective review of all 166 (114 native and 52 prosthetic) patients operated between January 2004 and March 2015 was performed. Long-term survival and repeat hospitalization data for 134 of 166 patients were obtained via linked clinical databases with the Manitoba Centre for Health Policy. Kaplan-Meier estimates of survival and hospital readmission and Cox multivariable regression analysis of factors influencing outcomes were performed. Survival at 1 and 5 years was 91% and 80%, respectively, and major adverse prosthesis-related event repeat hospitalization rates were 12% and 21%, respectively. Repeat hospitalization because of endocarditis was 7% and 11% at 1 and 5 years, respectively. Survival and repeat hospitalization were similar for aortic and mitral valves. Survival after surgically treated endocarditis was similar to survival for age-, sex-, and valve-matched surgical valve replacements for noninfectious indications (P = 0.53). Viridans Streptococci was the most common organism in native valve endocarditis, and culture negative endocarditis was most common in prosthetic valves. Prosthetic valve endocarditis (P 0.01) and preoperative renal dysfunction (P 0.01) were risk factors for in-hospital mortality and major postoperative adverse events. Diabetes and renal dysfunction were associated with poor long-term survival, functional survival, and repeat hospitalization. This analysis suggests that surgery remains a very effective tool in management of these complex patients in terms of survival and major adverse prosthesis-related event repeat hospitalization.

RNA Helicase associated with AU-rich element (RHAU) (DHX36) is a DEAH (Aspartic acid, Glumatic Acid, Alanine, Histidine)-box RNA helicase that can bind and unwind G4-quadruplexes in DNA and RNA. To detect novel RNA targets of RHAU, we performed an RNA co-immunoprecipitation screen and identified the PITX1 messenger RNA (mRNA) as specifically and highly enriched. PITX1 is a homeobox transcription factor with roles in both development and cancer. Primary sequence analysis identified three probable quadruplexes within the 3′-untranslated region of the PITX1 mRNA. Each of these sequences, when isolated, forms stable quadruplex structures that interact with RHAU. We provide evidence that these quadruplexes exist in the endogenous mRNA; however, we discovered that RHAU is tethered to the mRNA via an alternative non–quadruplex-forming region. RHAU knockdown by small interfering RNA results in significant increases in PITX1 protein levels with only marginal changes in mRNA, suggesting a role for RHAU in translational regulation. Involvement of components of the microRNA machinery is supported by similar and non-additive increases in PITX1 protein expression on Dicer and combined RHAU/Dicer knockdown. We also demonstrate a requirement of argonaute-2, a key RNA-induced silencing complex component, to mediate RHAU-dependent changes in PITX1 protein levels. These results demonstrate a novel role for RHAU in microRNA-mediated translational regulation at a quadruplex-containing 3′-untranslated region.

Polynucleotides containing consecutive tracts of guanines can adopt an intramolecular G-quadruplex structure where multiple planar tetrads of hydrogen-bound guanines stack on top of each other. Remodeling of G-quadruplexes impacts numerous aspects of nucleotide biology including transcriptional and translational control. RNA helicase associated with AU-rich element (RHAU), a member of the ATP-dependent DEX(H/D) family of RNA helicases, has been established as a major cellular quadruplex resolvase. RHAU contains a core helicase domain responsible for ATP binding/hydrolysis/helicase activity and is flanked on either side by N- and C-terminal extensions. The N-terminal extension is required for quadruplex recognition, and we have previously demonstrated complex formation between this domain and a quadruplex from human telomerase RNA. Here we used an integrated approach that includes small angle x-ray scattering, nuclear magnetic resonance spectroscopy, circular dichroism, and dynamic light scattering methods to demonstrate the recognition of G-quadruplexes by the N-terminal domain of RHAU. Based on our results, we conclude that (i) quadruplex from the human telomerase RNA and its DNA analog both adopt a disc shape in solution, (ii) RHAU53–105 adopts a defined and extended conformation in solution, and (iii) the N-terminal domain mediates an interaction with a guanine tetrad face of quadruplexes. Together, these data form the foundation for understanding the recognition of quadruplexes by the N-terminal domain of RHAU.