Methylation at the promoter region is associated with gene silencing. Methylation of DNA is a common method of gene silencing. This variant is associated with gene activation, silencing and suppression of antisense RNA. This may weaken the effects of gene silencing mechanisms that occur prior to methylation. This makes the mechanism of gene silencing catalytic. RNAi drugs treat cancer by silencing certain cancer promoting genes. The cause of the epigenetic silencing is unknown. These modifications coincide with the transcriptional silencing of the X-linked genes. MREs are sequences to which miRNAs bind and cause gene silencing. RNA silencing mechanisms are highly conserved in most eukaryotes. Cas9 is an effective way of targeting and silencing specific genes at the DNA level. RISC is responsible for the gene silencing phenomenon known as RNA interference (RNAi). Evidence suggests that RNA silencing is involved in the process. DNA double-strand breaks appear to be initiation sites for meiotic silencing. The first test of Lincoln's thesis for silencing dissenters occurred in the spring of 1863.