R-loops are three-stranded structures generated by annealing of nascent transcripts to the template DNA strand, leaving the non-template DNA strand exposed as a single-stranded loop. Although R-loops play important roles in physiological processes such as regulation of gene expression, mitochondrial DNA replication, or immunoglobulin class switch recombination, dysregulation of the R-loop metabolism poses a threat to the stability of the genome. A previous study in yeast has shown that the homologous recombination machinery contributes to the formation of R-loops and associated chromosome instability. On the contrary, here, we demonstrate that depletion of the key homologous recombination factor, RAD51, as well as RAD51 inhibition by the B02 inhibitor did not prevent R-loop formation induced by the inhibition of spliceosome assembly in human cells. However, we noticed that treatment of cells with B02 resulted in RAD51-dependent accumulation of R-loops in an early G1 phase of the cell cycle accompanied by a decrease in the levels of chromatin-bound ORC2 protein, a component of the pre-replication complex, and an increase in DNA synthesis. Our results suggest that B02-induced R-loops might cause a premature origin firing.

• MeSH
• chromozomální nestabilita účinky léků   MeSH
• DNA biosyntéza   MeSH
• G1 fáze účinky léků   MeSH
• inhibitory enzymů farmakologie   MeSH
• komplex rozpoznávající replikační počátek metabolismus   MeSH
• lidé MeSH
• nádorové buněčné linie MeSH
• R-smyčka * MeSH
• rekombinasa Rad51 * antagonisté a inhibitory   metabolismus   MeSH
• Check Tag
• lidé MeSH
• Publikační typ
• časopisecké články MeSH

Present-day oncology sees at least two-thirds of cancer patients receiving radiation therapy as a part of their anticancer treatment. The objectives of the current study were to investigate the effects of the small molecule inhibitors of Wee1 kinase II (681641) and Rad51 (RI-1) on cell cycle progression, DNA double-strand breaks repair and apoptosis following ionizing radiation exposure in human leukemic T-cells Jurkat and MOLT-4. Pre-treatment with the Wee1 681641 or Rad51 RI-1 inhibitor alone increased the sensitivity of Jurkat cells to irradiation, however combining both inhibitors together resulted in a further enhancement of apoptosis. Jurkat cells pre-treated with inhibitors were positive for γH2AX foci 24h upon irradiation. MOLT-4 cells were less affected by inhibitors application prior to ionizing radiation exposure. Pre-treatment with Rad51 RI-1 had no effect on apoptosis induction; however Wee1 681641 increased ionizing radiation-induced cell death in MOLT-4 cells.

• MeSH
• inhibitory proteinkinas farmakologie   MeSH
• ionizující záření MeSH
• jaderné proteiny antagonisté a inhibitory   MeSH
• Jurkat buňky MeSH
• leukemie T-buněčná enzymologie   genetika   patologie   MeSH
• lidé MeSH
• oprava DNA MeSH
• poškození DNA účinky záření   MeSH
• proteiny buněčného cyklu antagonisté a inhibitory   MeSH
• rekombinasa Rad51 antagonisté a inhibitory   MeSH
• tyrosinkinasy antagonisté a inhibitory   MeSH
• Check Tag
• lidé MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH