Occult hepatitis C virus elicits mitochondrial oxidative stress in lymphocytes and triggers PI3-kinase-mediated DNA damage response

The DNA damage response and repair (DDR/R) network, a sum of hierarchically structured signaling pathways that recognize and repair DNA damage, and the immune response to endogenous and/or exogenous threats, act synergistically to enhance cellular defense. On the other hand, a deregulated interplay between these systems underlines inflammatory diseases including malignancies and chronic systemic autoimmune diseases, such as systemic lupus erythematosus, systemic sclerosis, and rheumatoid arthritis. Patients with these diseases are characterized by aberrant immune response to self-antigens with widespread production of autoantibodies and multiple-tissue injury, as well as by the presence of increased oxidative stress. Recent data demonstrate accumulation of endogenous DNA damage in peripheral blood mononuclear cells from these patients, which is related to (a) augmented DNA damage formation, at least partly due to the induction of oxidative stress, and (b) epigenetically regulated functional abnormalities of fundamental DNA repair mechanisms. Because endogenous DNA damage accumulation has serious consequences for cellular health, including genomic instability and enhancement of an aberrant immune response, these results can be exploited for understanding pathogenesis and progression of systemic autoimmune diseases, as well as for the development of new treatments.

Download Full-text

APE2 Is a General Regulator of the ATR-Chk1 DNA Damage Response Pathway to Maintain Genome Integrity in Pancreatic Cancer Cells

Frontiers in Cell and Developmental Biology ◽

10.3389/fcell.2021.738502 ◽

2021 ◽

Vol 9 ◽

Author(s):

Md Akram Hossain ◽

Yunfeng Lin ◽

Garrett Driscoll ◽

Jia Li ◽

Anne McMahon ◽

...

Keyword(s):

Oxidative Stress ◽

Pancreatic Cancer ◽

Dna Damage ◽

Cancer Cells ◽

Dna Damage Response ◽

Human Pancreatic Cancer ◽

Genome Integrity ◽

Pancreatic Cancer Cells ◽

Damage Response ◽

Egg Extracts

The maintenance of genome integrity and fidelity is vital for the proper function and survival of all organisms. Recent studies have revealed that APE2 is required to activate an ATR-Chk1 DNA damage response (DDR) pathway in response to oxidative stress and a defined DNA single-strand break (SSB) in Xenopus laevis egg extracts. However, it remains unclear whether APE2 is a general regulator of the DDR pathway in mammalian cells. Here, we provide evidence using human pancreatic cancer cells that APE2 is essential for ATR DDR pathway activation in response to different stressful conditions including oxidative stress, DNA replication stress, and DNA double-strand breaks. Fluorescence microscopy analysis shows that APE2-knockdown (KD) leads to enhanced γH2AX foci and increased micronuclei formation. In addition, we identified a small molecule compound Celastrol as an APE2 inhibitor that specifically compromises the binding of APE2 but not RPA to ssDNA and 3′-5′ exonuclease activity of APE2 but not APE1. The impairment of ATR-Chk1 DDR pathway by Celastrol in Xenopus egg extracts and human pancreatic cancer cells highlights the physiological significance of Celastrol in the regulation of APE2 functionalities in genome integrity. Notably, cell viability assays demonstrate that APE2-KD or Celastrol sensitizes pancreatic cancer cells to chemotherapy drugs. Overall, we propose APE2 as a general regulator for the DDR pathway in genome integrity maintenance.

Download Full-text

Occult hepatitis C virus infection is more common than hepatitis B infection in maintenance hemodialysis patients

World Journal of Gastroenterology ◽

10.3748/wjg.14.288 ◽

2008 ◽

Vol 14 (14) ◽

pp. 2288

Author(s):

Pankaj Jain ◽

Sandeep Nijhawan

Keyword(s):

Hepatitis C Virus ◽

Hepatitis C ◽

Virus Infection ◽

Hemodialysis Patients ◽

Maintenance Hemodialysis ◽

Hepatitis B Infection ◽

Hepatitis C Virus Infection ◽

Occult Hepatitis ◽

Occult Hepatitis C ◽

Maintenance Hemodialysis Patients

Download Full-text

Characterization of Occult Hepatitis C Virus (Hcv) Infection among Hemodialysis Patient

IIUM Medical Journal Malaysia ◽

10.31436/imjm.v16i1.1138 ◽

2017 ◽

Vol 16 (1) ◽

Author(s):

Siti Nurul Fazlin Abdul Rahman ◽

Hairul Aini binti Hamzah ◽

Mohammed Imad Mustafa ◽

Mohamed Hadzri Hasmoni

Keyword(s):

Hepatitis C Virus ◽

Hepatitis C ◽

Hemodialysis Patients ◽

Hcv Infection ◽

Viral Rna ◽

Cell Counting ◽

Hcv Rna ◽

Viral Rnas ◽

Occult Hepatitis ◽

Occult Hepatitis C

Introduction: The existence of new entity called occult hepatitis C virus (HCV) has become a raising and escalating concern among healthcare professionals worldwide. It is defined by the presence of viral RNA in liver and/or peripheral blood mononuclear cells (PBMCs) within non HCV-infected patients. Previous study had shown the occult HCV is infectious and capable of transmitting the virus to another host. Till today, HCV infection remains common among hemodialysis patients despite having the best preventive plans. Because of this, there is a significant concern about the source of viral transmission. The aim of the study was to identify and characterize occult HCV infection in PBMC sample of hemodialysis patients. This was an observational and cross sectional study. Materials and method: PBMCs were isolated from the whole blood using Ficoll-gradient centrifugation technique. The PBMCs were then subjected for cell counting and stored in -70O C until further used. HCV RNA were extracted from these cells and viral RNA were subjected for molecular assays, immune cells analysis and cells culture. Results: PBMCs were isolated from eleven (11) study patients and five (5) anti-HCV positive (control) patients. By using automated flow cytometry, PBMCs of each sample were counted and the average number of cells obtained range from 2x104 to 5x106 cells/ ml. Viral RNAs were extracted and quantitatively measured by using NanoDrop Spectrophotometers. The viral RNAs concentration obtained were between 24.7 and 258.9 ng/ml. The RNAs would be subjected for purification (ethanol precipitation) and further assays. Conclusion: The final findings might contribute to the clinical management of dialysis patients.

Download Full-text

RTT109 AND Fun30 proteins mediate epigenetic regulation of the DNA damage response pathway in C. albicans

10.1101/2021.07.22.453354 ◽

2021 ◽

Author(s):

Prashant Kumar Maurya ◽

Pramita Garai ◽

Kaveri Goel ◽

Himanshu Bhatt ◽

Aarti Goyal ◽

...

Keyword(s):

Oxidative Stress ◽

Dna Damage ◽

Dna Damage Response ◽

Regulation Of Gene Expression ◽

Repair Pathway ◽

Fungal Cell ◽

Opportunistic Fungi ◽

Damage Response ◽

H3 Acetylation ◽

Dna Damage Response Pathway

Fun30, an ATP-dependent chromatin remodeller, from S. cerevisiae mediates both regulation of gene expression as well as DNA damage response/repair. In this paper, we have characterized the biochemical and physiological function of Fun30 from the opportunistic fungi, C. albicans. Biochemically, the protein shows DNA-stimulated ATPase activity. Physiologically, the protein co-regulates transcription of RTT109, TEL1, MEC1, and SNF2-genes that encode for proteins involved in DNA damage response and repair pathway. The expression of FUN30, in turn, is regulated by histone H3 acetylation catalysed by Rtt109 encoded by RTT109. The RTT109Hz/FUN30Hz mutant strain shows sensitivity to oxidative stress and resistance to MMS as compared to the wild type strain. Quantitative PCR showed that the sensitivity to oxidative stress results from downregulation of MEC1, RAD9, MRC1 and RAD5 expression; ChIP experiments showed Fun30 but not H3ac regulates the expression of these genes in response to oxidative stress. In contrast, on treatment with MMS, the expression of RAD9 is upregulated and this upregulation is co-regulated by both Fun30 and H3 acetylation catalysed by Rtt109. Thus, Fun30 and H3 acetylation mediate the response of the fungal cell to genotoxic agents in C. albicans by regulating the expression of DNA damage response and repair pathway genes.

Download Full-text