Figure 7.

PARP1 localizes at eroded telomeres induced by DNA damage or by loss of telomeric DNA in murine cells. TEL-FISH analysis of metaphase spreads of mTert-deficient ES cells with short telomeres and radiation-treated primary wild-type MEFs. PARP1 signals (in green) were observed at the chromosome ends with or without detectable telomeric DNA signals (in red) in (A) 5-Gy x-ray–treated MEFs or (B) late passages of telomerase-deficient mouse ES cells harboring short (passage 30) or critically short (passage 90) telomeres. (C) PARP1 signals found at chromosome end-to-end fusion sites without detectable telomeric DNA signals in mTert-deficient ES cells. (D) No punctate-like signals associated with the chromosomes of mParp1^–/– MEFs. Arrows, representative PARP1 signals at chromosome ends (in white) or interiors (in yellow).