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. 2019 May 8;5(5):eaav3673. doi: 10.1126/sciadv.aav3673

Fig. 6. SETDB1 controls ALT maintenance in human tumor cell lines.

Fig. 6

(A) Left: Coimmunostaining of SETDB1 (red) with TRF2 (green) in human ALT cell lines (VA13, U2OS, and MFH148) versus a human non-ALT cell line as a control (MFH152) cells. Right: Quantification of the percentage of SETDB1-TRF2 colocalization events. (B) Left: Coimmunostaining of TRF1 (red) with PML (green) to measure ALT-associated PML body formation upon SETDB1 knockdown in two ALT cell line U2OS and MFH148. Right: Quantification APB number per cell. *P < 0.05. (C) Top: C-circle assay in two ALT-positive cell lines and one negative cell line upon Scramble (SCR) or SETDB1 knockdown. (D) Proposed model derived from our main findings: SETDB1 mediates heterochromatin at telomeres, and the recruitment of ATRX is dependent of H3K9me3 deposition and prevents HR. SETDB1-dependent heterochromatin is recombinogenic and promotes ALT features in the absence of ATRX. A.U., arbitrary units; NS, not significant.