Human AP endonuclease suppresses DNA mismatch repair activity leading to microsatellite instability

The multifunctional mammalian apurinic/apyrimidinic (AP) endonuclease (APE) participates in the repair of AP sites in the cellular DNA as well as participating in the redox regulation of the transcription factor function. The function of APE is considered as the rate-limiting step in DNA base excision repair. Paradoxically, an unbalanced increase in APE protein leads to genetic instability. Therefore, we investigated the mechanisms of genetic instability that are induced by APE. Here, we report that the overexpression of APE protein disrupts the repair of DNA mismatches, which results in microsatellite instability (MSI). We found that expression of APE protein led to the suppression of the repair of DNA mismatches in the normal human fibroblast cells. Western blot analysis revealed that hMSH6 protein was markedly reduced in the APE-expressing cells. Moreover, the addition of purified Mutα (MSH2 and MSH6 complex) to the extracts from the APE-expressing cells led to the restoration of mismatch repair (MMR) activity. By performing MMR activity assay and MSI analysis, we found that the co-expression of hMSH6 and APE exhibited the microsatellite stability, whereas the expression of APE alone generated the MSI-high phenotype. The APE-mediated decrease in MMR activity described here demonstrates the presence of a new and highly effective APE-mediated mechanism for MSI

Direct observation of DNA target searching and cleavage by CRISPR-Cas12a

Cas12a (also called Cpf1) is a representative type V-A CRISPR effector RNA-guided DNA endonuclease, which provides an alternative to type II CRISPR-Cas9 for genome editing. Previous studies have revealed that Cas12a has unique features distinct from Cas9, but the detailed mechanisms of target searching and DNA cleavage by Cas12a are still unclear. Here, we directly observe this entire process by using single-molecule fluorescence assays to study Cas12a from Acidaminococcus sp. (AsCas12a). We determine that AsCas12a ribonucleoproteins search for their on-target site by a one-dimensional diffusion along elongated DNA molecules and induce cleavage in the two DNA strands in a well-defined order, beginning with the non-target strand. Furthermore, the protospacer-adjacent motif (PAM) for AsCas12a makes only a limited contribution of DNA unwinding during R-loop formation and shows a negligible role in the process of DNA cleavage, in contrast to the Cas9 PAM.

Predictive factors that influence the survival rates in liver cirrhosis patients with spontaneous bacterial peritonitis

Background/AimsSpontaneous bacterial peritonitis (SBP) has been known to greatly influence the survival rate of patients with liver cirrhosis. However, the factors that affect the survival rate in patients with SBP need to be clarified.MethodsThis study enrolled 95 liver cirrhosis patients diagnosed with SBP. The laboratory findings of their serum and ascitic fluid were examined and the characteristics of the isolated microorganisms in their peritoneal fluid were analyzed.ResultsThe proportion of patients with culture-positive SBP was 41.1%, and 47 microorganisms were isolated from the ascitic fluid. The proportions of cultured bacteria that were Gram negative and Gram positive were 57.4% and 40.4%, respectively. The proportions of Escherichia coli, Klebsiella species, and Streptococcus species were 25.5%, 19.1%, and 19.1%, respectively. Enterococcus species represented 12.8% of the microorganisms cultured. The overall survival rates at 6, 12, and 24 months were 44.5%, 37.4%, and 32.2%, respectively. There was no relationship between the bacterial factors and the survival rate in SBP. Multivariate analysis revealed that the presence of hepatocellular carcinoma (HCC; P=0.001), higher serum bilirubin levels (≥3 mg/dL, P=0.002), a prolonged serum prothrombin time (i.e., international normalized ratio >2.3, P1.3 mg/dL, P<0.001), and lower glucose levels in the ascitic fluid (<50 mg/dL, P<0.001) were independent predictive factors of overall survival rate.ConclusionsHCC, higher serum bilirubin levels, a prolonged serum prothrombin time, renal dysfunction, and lower ascitic glucose levels are associated with higher mortality rates in cirrhotic patients with SBP

Activated forkhead transcription factor inhibits neointimal hyperplasia after angioplasty through induction of p27

OBJECTIVE: We examined the effects of FKHRL1 (forkhead transcription factor in rhabdomyosarcoma like-1) overexpression on vascular smooth muscle cell (VSMC) proliferation, apoptosis, and cell cycle, in vitro, and the role of FKHRL1 and p27 in the pathophysiology of neointimal growth after balloon angioplasty, in vivo. Furthermore, we tested whether FKHRL1 overexpression can inhibit neointimal hyperplasia in a rat carotid artery model. METHODS AND RESULTS: Adenovirus expressing the constitutively active FKHRL1 (FKHRL1-TM; triple mutant) with 3 Akt phosphorylation sites mutated was transfected to subconfluent VSMCs. FKHRL1 overexpression in cultured VSMCs increased p27 expression, leading to G1 phase cell-cycle arrest and increased apoptosis. In vivo, the phosphorylation of FKHRL1 increased significantly 3 hours after balloon injury and decreased thereafter, with the subsequent downregulation of p27. Although the phosphorylation of FKHRL1 was greatest at 3 hours, the downregulation of p27 showed a temporal delay, only slightly starting to decrease after 3 hours and reaching a nadir at 72 hours after balloon injury. Gene transfer of FKHRL1-TM increased p27, decreased proliferation, and increased apoptosis of VSMCs, which resulted in a marked reduction in neointima formation (intima-to-media ratio: 0.31+/-0.13 versus 1.17+/-0.28, for FKHRL1-TM versus Adv-GFP; P<0.001). CONCLUSIONS: Balloon angioplasty leads to the phosphorylation of FKHRL1 and decreased expression of p27, thereby promoting a proliferative phenotype in VSMCs in vitro and in vivo. This study reveals the importance of FKHRL1 in proliferation and viability of VSMCs and suggests that it may serve as a molecular target for interventions to reduce neointima formation after angioplasty

Korean Ginseng-Induced Occupational Asthma and Determination of IgE Binding Components

A number of case reports on occupational asthma caused by herbal medicines have been issued, for example, on Sanyak, Chunkung, Banha, and Brazilian ginseng. Recently, cases of occupational asthma induced by Sanyak and Korean ginseng have been reported, but the pathogenic mechanisms involved are unknown. This study was carried out to evaluate the immunologic mechanism underlying Korean ginseng-induced occupational asthma. A patient engaged in Korean ginseng wholesale was referred for recurrent dyspnea, wheezing, and nasal symptoms, which were aggravated at work. Allergen bronchial provocation testing to Korean ginseng extract showed a typical immediate response, and skin prick testing to Korean ginseng extract also showed a strong positive response. Moreover, serum-specific IgE levels to Korean ginseng extract were significantly higher than in controls. Enzyme-linked immunosorbent assay (ELISA) inhibition tests showed a dose-dependent inhibition by Korean ginseng, but not by Dermatophagoides farinae, wheat flour, or Chinese balloon flower. Sodium dodecylsulfate-poly-acrylamide gel electrophoresis (SDS-PAGE) and immunoblotting revealed four specific Immunoglobulin E (IgE) binding components at 26, 30, 47, and 60 kDa, which were not bound by control sera. These results strongly suggest that occupation asthma induced by Korean ginseng is induced via an IgE-mediated mechanism

Angle-dependent optical perfect absorption and enhanced photoluminescence in excitonic thin films

We experimentally demonstrate perfect absorption of incident light in an ultrathin, planar organic layer, together with large photoluminescence (PL) enhancement. We find that diverse features appear in the absorption spectra of J-aggregate excitonic films, depending on the incident light angle and the phase controller thickness. We achieve strong absorption even away from the excitonic absorption pole. We explain the angle-dependent perfect absorption by comparing radiative and nonradiative damping rates for different incident angles. Moreover, we achieve large PL enhancement at strong light absorption conditions. This demonstrates that the absorbed light energy in excitonic perfect absorbers can be retrieved, unlike other perfect absorbers based on metal nanostructures where the absorbed energy is mainly dissipated as heat due to ohmic losses. Excitonic perfect absorbers can be useful for energy conversion devices or fluorescence-based optical devices