C Immunofluorescence showing gammaH2AX foci in HeLa shTRF2 cells at the indicated time points following doxycycline treatment and consequent TRF2 knockdown. Scale bar, 25 µm. D RT-qPCR detection of ACE2 mRNA expression levels in HeLa shTRF2 cells treated as in C (n = 6 independent experiments). 