In vitro methylation of HpaII sites in Xenopus laevis rDNA does not affect its transcription in oocytes.

The effect of methylation of X. laevis rDNA on its transcription was tested by methylating all of the HpaII sites in a series of rDNA plasmids and injecting the methylated rDNA into X. borealis oocytes. Analysis of RNA transcribed from the injected plasmids showed that methylation of rDNA in vitro does not affect transcription of X. laevis ribosomal genes. This result suggests that despite the observed correlation between demethylation of rDNA and synthesis of ribosomal RNA in X. laevis embryos (1), methylation of rDNA does not regulate transcription of the gene.