Kruppel-associated Box (KRAB)-associated co-repressor (KAP-1) Ser-473 phosphorylation regulates heterochromatin protein 1β (HP1-β) mobilization and DNA repair in heterochromatin. | LitMetric
The DNA damage response encompasses a complex series of signaling pathways that function to regulate and facilitate the repair of damaged DNA. Recent studies have shown that the repair of transcriptionally inactive chromatin, named heterochromatin, is dependent upon the phosphorylation of the co-repressor, Krüppel-associated box (KRAB) domain-associated protein (KAP-1), by the ataxia telangiectasia-mutated (ATM) kinase. Co-repressors, such as KAP-1, function to regulate the rigid structure of heterochromatin by recruiting histone-modifying enzymes, such HDAC1/2, SETDB1, and nucleosome-remodeling complexes such as CHD3. Here, we have characterized a phosphorylation site in the HP1-binding domain of KAP-1, Ser-473, which is phosphorylated by the cell cycle checkpoint kinase Chk2. Expression of a nonphosphorylatable S473A mutant conferred cellular sensitivity to DNA-damaging agents and led to defective repair of DNA double-strand breaks in heterochromatin. In addition, cells expressing S473A also displayed defective mobilization of the HP1-β chromodomain protein. The DNA repair defect observed in cells expressing S473A was alleviated by depletion of HP1-β, suggesting that phosphorylation of KAP-1 on Ser-473 promotes the mobilization of HP1-β from heterochromatin and subsequent DNA repair. These results suggest a novel mechanism of KAP-1-mediated chromatin restructuring via Chk2-regulated HP1-β exchange from heterochromatin, promoting DNA repair.
Background: The utilization of PD1 and CTLA4 inhibitors has revolutionized the treatment of malignant melanoma (MM). However, resistance to targeted and immune-checkpoint-based therapies still poses a significant problem.
Objective: Here, we mine large-scale MM proteogenomic data to identify druggable targets and forecast treatment efficacy and resistance.
Streptozotocin (STZ) is widely used as a pancreatic beta-cell toxin to induce experimental diabetes in rodents. Strain-dependent variations in STZ-induced diabetes susceptibility have been reported in mice. Differences in STZ-induced diabetes susceptibility are putatively related to pancreatic beta-cell fragility via DNA damage response.
Department of Neurosciences and Mental Health, Unidade Local de Saúde de Santa Maria, Lisbon, Portugal; Faculdade de Medicina-Instituto de Medicina Molecular, Centro de Estudos Egas Moniz, Universidade de Lisboa, Lisbon, Portugal.
Objective: To present cases of ptosis in HIV-1 patients on long-term antiretroviral therapy (ART) and review the existing literature.
Methods: Five HIV-1-positive patients with slowly progressive bilateral ptosis underwent a comprehensive diagnostic evaluation, including imaging studies, neurophysiological testing, muscle biopsy, and genetic analysis. A literature review was conducted.
Department of Chemistry and Biochemistry and the Milwaukee Institute for Drug Discovery, University of Wisconsin-Milwaukee, Milwaukee, Wisconsin 53211, United States.
DNA interstrand cross-links (ICLs) are the sources of the cytotoxicity of many anticancer agents. Selenium compounds showed great potential as anticancer drugs. In this work, we synthesized a binaphthalene analog containing phenyl selenide (-SePh) as the leaving group and investigated its photochemical reactivity toward DNA as well as its cytotoxicity and selectivity.
Despite the remarkable resistance of the nucleic acid phosphodiester backbone to degradation affording genetic stability, the P-O bond must be broken during DNA repair and RNA metabolism, among many other critical cellular processes. Nucleases are powerful enzymes that can enhance the uncatalyzed rate of phosphodiester bond cleavage by up to ∼10-fold. Despite the most well accepted hydrolysis mechanism involving two metals (M to activate a water nucleophile and M to stabilize the leaving group), experimental evidence suggests that some nucleases can use a single metal to facilitate the chemical step, a controversial concept in the literature.
