Mirin

Mirin inhibits DSB-induced ATM activation, the ATM-dependent phosphorylation of the downstream targets Nbs1 and Chk2 and the MRN-dependent autophosphorylation of ATM at Ser1981 in response to DSBs. Mirin also inhibits the G2 checkpoint in TOSA4 cells, and homology-dependent DNA repair in HEK293 cells. ^[1]

In cells with integrated HPV16 (SiHa), Mirin sensitizes HPV episomes to PA25 resulting in a ∼5-fold reduction of the PA25 IC50. ^[2]

Pretreatment with mirin also decreases cell viability and inhibits proliferating cell nuclear antigen expression in cisplatin-treated human embryonic kidney 293 cells. ^[3]

Mirin in nanoparticles resulted in a sharp impairment of tumor growth, associated with DDR activation, p53 accumulation, and cell death.

• Nuclease assay

  Reactions with oligonucleotide nonhairpin substrates contains 25 mM MOPS (pH 7.0), 60 mM KCl, 0.2% Tween 20, 2 mM DTT, 1 mM or 5 MnCl₂ (or 5 mM MgCl₂, or 5 mM CaCl₂), 0.1 pmol of DNA substrate, and 0.3 pmol of Mre11 (or an equivalent amount of Mre11 complexed with Rad50) in a volume of 10 μl, and are incubated at 37°C for 30 min. SDS, EDTA, and proteinase K are then added to final concentrations of 0.2%, 5 mM, and 0.1 mg/ml, respectively, and incubated for another 15 min. 4 μl of each reaction is mixed with 4 μl of formamide loading buffer, and then loaded onto a sequencing gel containing 10% acrylamide and 7 M urea. After the run, each gel is analyzed using a phosphorimaging system. Reactions containing hairpin substrates are identical to those with nonhairpin substrates except that 3 pmol of Mre11 is added to reactions as indicated, and the reactions are incubated at room temperature overnight. Nonhomologous end-joining reactions contains 25 mM MOPS (pH 7.0), 60 mM KCl, 0.2% Tween 20, 2 mM DTT, 4 mM MgCl₂, 2 mM MnCl₂, 0.5 mM ATP, 4 ng of plasmid DNA, 10% polyethylene glycol, 0.01 pmol of human DNA ligase I, and 0.06 pmol of Mre11 or 0.1 units of E. coli exonuclease III (GIBCO-BRL), in a volume of 10 μl. After incubation at 37°C for 25 min, Tween 20 is added to a final concentration of 0.5%, and a 2.5 μl aliquot is amplified by PCR using primers DAR5 and DAR147. PCR products are cloned using the TA cloning kit and sequenced using an automated ABI Capillary Genetic Analyzer.

• Cell lines

  HEK 293 cells

• Concentrations

  100 μM

• Incubation Time

  24 h

• Method

  Human embryonic kidney (HEK) 293 cells are maintained in RPMI-1640 supplemented with 5% heat-inactivated fetal bovine serum, penicillin (100 U/mL), and streptomycin (100 mg/mL) in humidified air with 5% CO₂ at 37 °C. Cells are given fresh medium at 48 h intervals. The cells are seeded in 96-well plates in regular growth medium. Cells are pretreated with mirin (100 μM for 1 h before the cisplatin (20 μM) treatment followed by incubation for 8 and 24 h. The MTT assay is performed using the EZ-Cytox cell viability assay kit according to the manufacturer's protocol and MTT reduction is measured at a 450 nm wavelength using a micro-plate reader.