Transcription is regulated by acetylation/deacetylation reactions of histone and nonhistone proteins mediated by enzymes called KATs and HDACs, respectively. As a major mechanism of transcriptional regulation, protein acetylation is a key controller of physiological processes such as cell cycle, DNA damage response, metabolism, apoptosis, and autophagy. The deacetylase activity of class III histone deacetylases or sirtuins depends on the presence of NAD⁺ (nicotinamide adenine dinucleotide), and therefore, their function is closely linked to cellular energy consumption. This activity of sirtuins connects the modulation of chromatin dynamics and transcriptional regulation under oxidative stress to cellular lifespan, glucose homeostasis, inflammation, and multiple aging‐related diseases including cancer. Here we provide an overview of the recent developments in relation to the diverse biological activities associated with sirtuin enzymes and stress responsive transcription factors, DNA damage, and oxidative stress and relate the involvement of sirtuins in the regulation of these processes to oncogenesis. Since the majority of the molecular mechanisms implicated in these pathways have been described for Sirt1, this sirtuin family member is more extensively presented in this paper.

For many years, circular ribonucleic acids (circRNAs) have been counted as aberrant splicing by-products. Advanced bioinformatics analysis and deep sequencing techniques have allowed researchers to discover more interesting facts about circRNAs. Intriguing evidence has shed light on the functions of circRNAs in many tissues. Furthermore, emerging reports showed that circRNAs are found abundantly in saliva and blood samples, suggesting that circRNAs are potential clinical biomarkers for human embryonic development, diseases progression and prognosis, in addition to its role in organogenesis and pathogenesis. The implementation of circRNAs in human developmental stages and diseases would be a tremendous discovery in the science and medical field. Therefore, circRNAs have been studied for its biological function as well as its implication in various human diseases. The aim of this review is to highlight the importance of circRNAs in cardiac, respiratory, nervous, endocrine and digestive systems. In addition, the role and impact of circRNAs in, cardiogenesis, neurogenesis and cancer have been discussed.

Introduction: The cytochrome P450 (CYP) enzymes are a class of heme-containing enzymes involved in phase I metabolism of a large number of xenobiotics. The CYP family member CYP2E1 metabolises many xenobiotics and pro-carcinogens, it is not just expressed in the liver but also in many other tissues such as the kidney, the lung, the brain, the gastrointestinal tract and the breast tissue. It is induced in several pathological conditions including cancer, obesity, and type II diabetes implying that this enzyme is implicated in other biological processes beyond its role in phase I metabolism. Despite the detailed description of the role of CYP2E1 in the liver, its functions in other tissues have not been extensively studied. In this study, we investigated the functional significance of CYP2E1 in breast carcinogenesis.Methods: Cellular levels of reactive oxygen species (ROS) were measured by H₂DCFDA (2 2.9.2 2′,7′-dichlorodihydrofluorescein diacetate) staining and autophagy was assessed by tracing the cellular levels of autophagy markers using western blot assays. The endoplasmic reticulum stress and the unfolded protein response (UPR) were detected by luciferase assays reflecting the splicing of mRNA encoding the X-box binding protein 1 (XBP1) transcription factor and cell migration was evaluated using the scratch wound assay. Gene expression was recorded with standard transcription assays including luciferase reporter and chromatin immunoprecipitation.Results: Ectopic expression of CYP2E1 induced ROS generation, affected autophagy, stimulated endoplasmic reticulum stress and inhibited migration in breast cancer cells with different metastatic potential and p53 status. Furthermore, evidence is presented indicating thatCYP2E1gene expression is under the transcriptional control of the p53 tumor suppressor.Conclusions: These results support the notion that CYP2E1 exerts an important role in mammary carcinogenesis, provide a potential link between ethanol metabolism and breast cancer and suggest that progression, and metastasis, of advanced stages of breast cancer can be modulated by induction of CYP2E1 activity.

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