Immunoblotting analysis and ELISA for p53 knockdown verification in HaCaT keratinocytes

To perform the knockdown, we applied lentiviral particles (LVPs) encoding anti-TP53 shRNA pLKO-p53-shRNA (Addgene, #25637). To assemble the LVPs, the pLKO-p53-shRNA was delivered in HEK293T cells using PEI transfection. The condition medium was collected 48-72 hours post transfection and purified from cell debris via centrifugation (45 min at 4500g and 4° C).

HaCaT cells were grown until 70% confluence, then the cultivation medium was replaced with condition medium containing LPVs for 1.5 hours. The cells were cultured for 4 days under standard conditions, afterwards the medium was replaced with puromycin-containing medium (1 µg/ml). As a control, we used HaCaT cells transduced with lego-ig2 (Addgene, #27341), which does not contain the puromycin resistance gene.

After 10 days of puromycin selection 100% of control cells were dead. The obtained cells were used for further experiments. For the immunosorbent assay, the cells were seeded at density of 1×104 cells per well 48 hours prior analysis.

ELISA was performed via Abcam’s assay (ab205713) for semi-quantitative p53 determination in accordance with the supplier's manual. For blotting analysis, the cells were grown until confluence of 70% at 60 mm Petri dishes under standard conditions. The cells were rinsed with DPBS and lysed in RIPA buffer (150 mM NaCl, 1% Triton X-100, 0.5% sodium deoxycholate, 0.1% SDS, 50 mM Tris, pH 8.0).

Then 4x Laemmli buffer was mixed with the samples to 1x followed by 10 min incubation at 90C. The proteins were separated in 8% sodium SDS-PAGE and transfered to PVDF membrane. The immunodetection was performed with antibodies to human p53 (clone BP-53-12, PrimeBioMed, Russia) and β-actin (Bio-rad, VMA00048).

Alkaline phosphatase (AP)-conjugated secondary antibodies (Bio-rad, STAR108A) were used for the immunodetection. The chemiluminescence was detected with DNR LumiBis Gel Imaging System 3.2. The images were obtained using GelCapture software.

Here we deposit the immunoblotting results confirming decrease of p53 level in p53 knockdown HaCaT cells. The provided data includes the results of 3 independent experiments. Also, we present the raw data obtained from the ELISA assay.