FIG. 1.

RECQ1 and RECQ4 helicases are recruited to human origins of DNA replication. (A and B) Genomic regions containing the lamin B2 origin (A) and two GM-CSF replication origins (B) are shown together with the locations of sets of primers (converging arrow pairs) used for quantitative real-time PCR analysis. (C) Quantification of cross-linked lamin B2 origin DNA immunoprecipitated by ChIP from T98G and IMR-90 cells, using the antibodies indicated at the bottom. The inset shows the results of Western analysis after immunoprecipitation of the cross-linked material with specific antibodies against the five human RecQ proteins. ORC2-specific immunoprecipitation served as a positive control, and rabbit IgG immunoprecipitation served as a negative control. Whole T98G cell lysates (WCL) were used to confirm the endogenous expression of the five RecQ helicases. (D) Quantification of cross-linked GM-CSF1 and GM-CSF2 origin DNAs immunoprecipitated by ChIP from T98G cells, using the antibodies indicated at the bottom. Fold enrichments of origin sequences were determined versus nonorigin control sequences, and the dashed line indicates the threshold enrichment level obtained by using a negative-control antibody (normal rabbit IgG). Results are reported as means ± standard errors of the means (SEM) (indicated by error bars) for at least three independent experiments.