Fig 1: The dissolvase complex stimulates C-circles formation and promotes checkpoint activation and ssDNA formation in FANCM deficient ALT cells. (A–D) U-2 OS cells were transfected with siRNA targeting luciferase (siLuc), BLM, RMI1, TOP3A, together with either FANCM siRNA (siFM-U) (labelled as FANCM deficient U-2 OS) or with siLuc (labelled as FANCM proficient U-2 OS). Genomic DNA was extracted and used for C-circle assay. “−Φ” indicates samples with no Phi(Φ)29 DNA polymerase added. The amount of C-circles in siLuc transfected cells is used to normalize C-circles in other siRNA transfected cells. (E–J) siRNA transfected U2-OS cells were co-stained with antibodies recognizing BLM and TRF1, or pChk1 and TRF1, or pRPA and TRF1. All error bars are standard deviation of the mean obtained from three different experiments. Standard two-tailed Student’s t-test: *p < 0.05, **p < 0.01, ***p < 0.001, ns – not significant.