Inhibition of DNA methylation results in reactivation of IgH transcription. (A) Map of the V_H region showing the location of primers used for RT-PCR analysis of IgH expression. Location of the forward primer in the leader regions enables the discrimination between spliced mRNA and genomic DNA contamination. V indicates variable; D, diversity; and J, joining. (B) Detection of Ig transcription in cHL cells by RT-PCR. L428, L1236, and KM-H2 cells were incubated for 72 hours in the presence of the indicated concentrations of 5-aza-dC. Total RNA was extracted from 1 × 10⁶ cells and converted to cDNA. The specifically amplified products were detected by ethidium bromide staining on agarose gels. Sizes of the PCR products are indicated in Table 1.