Figure 4.

Methylation analysis of promoter regions of X-linked genes. Genomic DNA prepared from various sources was digested with methylation-sensitive enzymes. Digestion was monitored by a PCR assay with primers that spanned several restriction sites. Methylated sequences escape digestion and can serve as template in the PCR. Undigested genomic DNA provided a positive control for the PCR assay (lane 1). PCR assays were performed on digested DNA isolated from female (293) cells (lane 2), male (lymphoblastoid) cells (lane 3), and human/hamster cell hybrids containing either the Xi (lane 4) or Xa (lane 5). PCR primers were the same as used to assess the H4 acetylation status shown in Table 2.