In earlier work, we demonstrated that 5'-CG-3' methylation inhibits the 
transcriptional activity of human Alu elements associated with the alpha 
1-globin and the angiogenin genes in a cell-free transcription system from HeLa 
nuclear extracts. These studies have been extended to different Alu sequences 
and to investigations on the mechanism involved in transcriptional silencing by 
methylation. By comparing the results of DNase I and dimethyl sulfate (DMS) in 
vitro footprinting on a consensus sequence in the RNA polymerase III promoter 
control B region between the unmethylated and the 5'-CG-3' methylated B box, 
evidence has been adduced for effects of 5'-CG-3' methylation on the interaction 
of specific nuclear proteins with DNA sequences in the B control region of the 
Alu elements. These results are consistent with the interpretation that the 
5'-CG-3' methylation interferes with the binding of proteins that are essential 
for the function of the B control region in these RNA polymerase III-transcribed 
elements, and that promoter methylation thus inhibits transcription.