FIG. 3.
Redundant functional domains of Cfp1 are sufficient to rescue reduced cytosine methylation in CXXC1−/− ES cells. A. Global cytosine methylation levels were determined by methyl acceptance assay for genomic DNA isolated from CXXC1+/+, CXXC1−/−, and CXXC1−/− ES cells expressing full-length Cfp1 (1-656) or the indicated Cfp1 fragments (or carrying the empty expression vector). The graph represents the results from three independent experiments, and error bars represent standard error. Asterisks denote statistically significant (P < 0.05) differences compared to CXXC1−/− ES cells expressing Cfp11-656. (B) Genomic DNA was isolated from the indicated ES cell lines and digested with MspI or HpaII, and Southern blot analysis was performed using a radiolabeled probe specific for IAP retrovirus repetitive elements. Arrows indicate bands that demonstrate cytosine hypomethylation. (C) Western blot analysis was performed on protein extracts collected from the indicated ES cell lines, using antiserum directed against Dnmt1 (7). The blot was reprobed for β-actin as a loading control. The graph summarizes the results from at least three independent experiments, and error bars represent standard error. Asterisks denote statistically significant (P < 0.05) differences compared to CXXC1−/− ES cells expressing Cfp11-656.