Western blot analysis of the KD of SAMHD1 or TOP1 by the transfection of CH12F3-2A cells by SAMHD1 siRNA or by tetracycline (50 nM) treatment, respectively. Expression of Tubulin is shown as a loading control (e: left). Relative expression of TOP1 and SAMHD1 as determined by densitometric quantification of western blot images in Fig. 3e (e: right). 