RNA extraction and qRT-PCR

RNA was isolated from S. flexneri and Panc-1 cells as previously described (67). Briefly, cells were lysed in TRIzol (Invitrogen) and heated to 65°C for 20 min, prior to the addition of chloroform and phase separation. RNA was then extracted from samples using the RNeasy Mini Kit (Qiagen) and purified using the RNase-free DNase I on-column treatment (Qiagen) according to manufacturer’s instructions. RNA extracts were then used in qRT-PCR, which was performed using the SuperScript III One-Step RT-PCR kit (ThermoFisher Scientific) on CFX 96 Opus System (Bio-Rad). Gene transcript levels for bacterial and Panc-1 samples were corrected against those obtained for gyrB or HIST1H3A housekeeping genes, respectively. All oligonucleotide sequences used for cDNA transcript amplification are specified in Table S2.