FIG. 2.
Chromosomal aberrations and checkpoint activation in Mus81−/− MEFs. (A) The DNA content of early-passage Mus81−/−, Mus81+/−, and wild-type MEFs was determined by flow cytometric analysis of propidium iodide-stained cells. (B) The cell cycle distribution of E6-expressing Mus81−/−, Mus81+/−, and wild-type cells was determined by flow cytometric analysis of bromodeoxyuridine- and propidium iodide-stained cells. (C) Phosphorylation of the Chk1 kinase was elevated in Mus81−/− cells prior to the addition of HU. The abundance of the Chk1 protein is not altered. Tubulin was monitored to ensure equal loading. (D) Chromosomal aberrations are increased in metaphase spreads from Mus81−/− MEFs. (E) Representative metaphase spreads from Mus81−/− cells.