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. Author manuscript; available in PMC: 2009 Apr 14.
Published in final edited form as: Cell Cycle. 2009 Apr 2;8(7):1036–1043. doi: 10.4161/cc.8.7.8040

Figure 3. Chk1, but not Claspin, is required to suppress origin firing during replication block.

Figure 3

(A) HeLa cells transfected with the indicated siRNA were labeled with 25μM BrdU for 10 minutes followed by 250μM IdU for 40 minutes in the presence or absence of aphidicolin. The level of origin firing measured in at least 100 replication tracks from three independent experiments is plotted. Error bars are standard error of the mean. (B) HeLa cells transfected with control (siCon), Chk1 (siChk1) or Claspin (siClasp) siRNA were treated with 15μM aphidicolin for 40 minutes or left untreated. The extent of Chk1 phosphorylation was monitored using anti-P-Ser345. Total levels of Chk1 and Claspin in cells were determined by probing with the relevant antibodies. Ku80 was used as a loading control.