Methylation- and mutation-dependent stimulation of Alu transcription in vitro.

Alu genes are GC-rich, highly repetitive genetic elements whose functions remain unknown. Members of this family are readily transcribed in vitro by RNA polymerase III, but RNA corresponding to only a small sub-set of Alu elements has been found in vivo. Based on the hypothesis that methylation of Alu elements affects their transcription, the transcriptional activity of unmethylated and methylated template DNA was assessed in vitro. It was found that methylation of a single CG site just 5' to Alu functions to stimulate transcription; the base composition in this region also affects transcriptional activity. These results indicate that the methylation state and sequence of DNA flanking Alu elements influence its transcription rate.