Role of Ape1 acetylation in fine tuning its activity on telomeric regions

One of the hallmarks of cancer is loss of telomeres stability. Unprotected telomeres are prone to aberrant end-joining reactions that lead to chromosomal fusions and translocations. Human telomeres are formed by the repeated TTAGGG sequence, in which the 3\u2019 exposed strand may adopt a G-quadruplex (G4) structure. The guanine-rich regions of telomeres are hotspots for oxidation forming 8-oxoguanine, a lesion that is handled by the base excision repair (BER) pathway. One key player of this pathway is Ape1, the main human endonuclease processing abasic sites. Recent evidences showed an important role for Ape1 in telomeric physiology, but the molecular details regulating Ape1 enzymatic activities on G4- telomeric sequences are lacking. Through a combination of in vitro assays, we demonstrate that Ape1 can bind and process different G4 structures containing abasic site analog (THF) in two different locations and that the interaction involves specific acetylatable lysine residues (i.e. K27/K31/K32/K35) present in the unstructured N-terminal domain of the protein. The cleavage of an abasic site located in a G4 structure by Ape1 depends on the DNA conformation or the position of the lesion and on electrostatic interactions between the protein and the nucleic acids. Moreover, Ape1 mutants mimicking the acetylated protein display increased cleavage activity for abasic sites. We found that nucleophosmin (NPM1), which binds the N-terminal domain of Ape1, plays a role in modulating telomere length and Ape1 activity at abasic G4 structures. Thus, the Ape1 N-domain is an important relay site for regulating the enzyme\u2019s activity on G4-telomeric sequences, and specific acetylatable lysine residues constitute key regulatory sites of Ape1 enzymatic activity dynamics at telomeresOne of the hallmarks of cancer is loss of telomeres stability. Unprotected telomeres are prone to aberrant end-joining reactions that lead to chromosomal fusions and translocations. Human telomeres are formed by the repeated TTAGGG sequence, in which the 3\u2019 exposed strand may adopt a G-quadruplex (G4) structure. The guanine-rich regions of telomeres are hotspots for oxidation forming 8-oxoguanine, a lesion that is handled by the base excision repair (BER) pathway. One key player of this pathway is Ape1, the main human endonuclease processing abasic sites. Recent evidences showed an important role for Ape1 in telomeric physiology, but the molecular details regulating Ape1 enzymatic activities on G4- telomeric sequences are lacking. Through a combination of in vitro assays, we demonstrate that Ape1 can bind and process different G4 structures containing abasic site analog (THF) in two different locations and that the interaction involves specific acetylatable lysine residues (i.e. K27/K31/K32/K35) present in the unstructured N-terminal domain of the protein. The cleavage of an abasic site located in a G4 structure by Ape1 depends on the DNA conformation or the position of the lesion and on electrostatic interactions between the protein and the nucleic acids. Moreover, Ape1 mutants mimicking the acetylated protein display increased cleavage activity for abasic sites. We found that nucleophosmin (NPM1), which binds the N-terminal domain of Ape1, plays a role in modulating telomere length and Ape1 activity at abasic G4 structures. Thus, the Ape1 N-domain is an important relay site for regulating the enzyme\u2019s activity on G4-telomeric sequences, and specific acetylatable lysine residues constitute key regulatory sites of Ape1 enzymatic activity dynamics at telomere

Serum AP-endonuclease 1 (sAPE1) as novel biomarker for hepatocellular carcinoma

Late diagnosis for Hepatocellular Carcinoma (HCC) remains one of the leading causes for the high mortality rate. The apurinic/apyrimidinic endonuclease 1 (APE1), an essential member of the base excision DNA repair (BER) pathway, contributes to cell response to oxidative stress and has other non-repair activities. In this study, we evaluate the role of serum APE1 (sAPE1) as a new diagnostic biomarker and we investigate the biological role for extracellular APE1 in HCC. sAPE1 level was quantified in 99 HCC patients, 50 non-HCC cirrhotic and 100 healthy controls. The expression level was significantly high in HCC (75.8 [67.3\u201387.9] pg/mL) compared to cirrhosis (29.8 [18.3\u201336.5] pg/mL] and controls (10.8 [7.5\u201313.2] pg/mL) (p < 0.001). The sAPE1 level corresponded with its protein expression in HCC tissue. sAPE1 had high diagnostic accuracy to differentiate HCC from cirrhotic (AUC = 0.87, sensitivity 88%, specificity 71%, cut-off of 36.3 pg/mL) and healthy subjects (AUC 0.98, sensibility 98% and specificity 83%, cut-off of 19.0 pg/mL). Recombinant APE1, exogenously added to JHH6 cells, significantly promotes IL-6 and IL-8 expression, suggesting a role of sAPE1 as a paracrine pro-inflammatory molecule, which may modulate the inflammatory status in cancer microenvironment. We described herein, for the first time to our knowledge, that sAPE1 might be considered as a promising diagnostic biomarker for HCC

Ruolo del ponte disolfuro nel processo di aggregazione dei VHH

The misfolding of some proteins can lead to the formation of amyloid fibrils, that are insoluble aggregates, which can lead to some neurodegenerative diseases. Some proteins aggregate after the removal of a disulfide bridge. We used nanobodies as model proteins to better understand the role of the SS bridge on the aggregation propensity of lg-G-folded proteins. Proteins without SS bridge form amyloid fibrils when incubated at pH 2 in several denaturant concentration

Trapianto di fegato in tarda adolescenza e giovane et\ue0 adulta. Risultati emersi dall\u2019indagine qualitativa realizzata all\u2019interno di un progetto pilota condotto presso l\u2019Azienda Ospedaliera \u2013 Universit\ue0 di Padova

L'abstract presenta uno studio osservazionale condotto su di un gruppo di giovani sottoposti a trapianto di fegato con finalit\ue0 educative di ascolto e comprensione delle loro vicende esistenziali. Lo studio \ue8 stato svolto all\u2019interno di un progetto pilota condotto presso l\u2019Azienda Ospedaliera \u2013 Universit\ue0 di Padov

ОБРАЗЫ «ЮРОДИВЫХ» И «УБОГИХ» В СОВРЕМЕННОМ РУССКОМ «ЖИТИЙНОМ» РАССКАЗЕ

Il presente progetto pilota \ue8 finalizzato alla creazione e attuazione di interventi di educazione alla salute (mediati dall\u2019uso di strumenti dialogici originali) in un gruppo di 14 pazienti sottoposti a trapianto di fegato in et\ue0 infantile. I pazienti, in una fascia di et\ue0 compresa tra tarda adolescenza e giovane et\ue0 adulta, sono parimenti coinvolti in un processo di transizione dal servizio pediatrico al servizio per adulti. Ciascuna persona \ue8 stata coinvolta nello studio per 10 mesi; ogni paziente \ue8 stato allocato mediante randomizzazione nel gruppo sperimentale (partecipa agli incontri) o di controllo (non partecipa). Sono stati utilizzati metodi di ricerca misti: i) analisi statistica dell\u2019efficacia degli interventi (somministrazione pre e post di una batteria di 5 questionari); ii) analisi qualitativa di interviste semi-strutturate (condotte con l\u2019intero gruppo) e dei contenuti emersi nel corso degli incontri (con gruppo sperimentale). Lo studio, iniziato a luglio 2015, si \ue8 concluso a ottobre 2016

Comparison of Fondaparinux and Low-Molecular-Weight Heparin in the Treatment of Portal Vein Thrombosis in Cirrhosis

Background: Portal vein thrombosis is the most common thrombotic complication in cirrhosis. About 60% of anticoagulated patients can achieve recanalization. Despite fondaparinux (FPX) theoretical advantages, data are lacking about safety and efficacy for treatment of portal vein thrombosis in cirrhosis. Methods: Cirrhotic patients with portal vein thrombosis treated with FPX or low-molecular-weight heparin (LMWH) were retrospectively included. The extension of thrombosis at baseline and its evolution during anticoagulant treatment were evaluated. Patients were treated with LMWH or FPX at therapeutic dosage and reduction was considered in selected cases. Results: There were 124 patients included. Main portal vein branch, splenic, and superior mesenteric veins were involved in 84%, 13%, and 36% of cases, respectively. Forty-one patients (33%) were treated with FPX and 83 (67%) with LMWH. The probability of resolution of thrombosis at 36 months was significantly higher in patients treated with FPX than in those treated with LMWH (77% vs 51%; P = .001), particularly when prescribed at reduced dose. With multivariate analysis, the treatment with FPX (hazard ratio 2.38; P = .002) and use of a full dose (hazard ratio 1.78; P = .035) were independent predictors of portal vein full recanalization. Bleeding rate was higher in patients treated with FPX than in those treated with LMWH (27% vs 13%; P = .06). Conclusions: FPX appears to be more effective than LMWH in the treatment of portal vein thrombosis when used at reduced dose, also in complete thrombosis. FPX should be considered among possible treatments for portal vein thrombosis in cirrhosis

Female gender in the setting of liver transplantation.

The evolution of liver diseases to end-stage liver disease or to acute hepatic failure, the evaluation process for liver transplantation, the organ allocation decision-making, as well as the post-transplant outcomes are different between female and male genders. Women's access to liver transplantation is hampered by the use of model for end-stage liver disease (MELD) score, in which creatinine values exert a systematic bias against women due to their lower values even in the presence of variable degrees of renal dysfunction. Furthermore, even when correcting MELD score for gender-appropriate creatinine determination, a quantifiable uneven access to transplant prevails, demonstrating that other factors are also involved. While some of the differences can be explained from the epidemiological point of view, hormonal status plays an important role. Moreover, the pre-menopausal and post-menopausal stages imply profound differences in a woman's physiology, including not only the passage from the fertile age to the non-fertile stage, but also the loss of estrogens and their potentially protective role in delaying liver fibrosis progression, amongst others. With menopause, the tendency to gain weight may contribute to the development of or worsening of pre-existing metabolic syndrome. As an increasing number of patients are transplanted for non-alcoholic steatohepatitis, and as the average age at transplant increases, clinicians must be prepared for the management of this particular condition, especially in post-menopausal women, who are at particular risk of developing metabolic complications after menopause