The present specification relates to an artificial manipulation or modification in an expression regulatory gene of an over-amplified repeated sequence. More specifically, a system for regulating the expression of an over-amplified repeated sequence including an artificially manipulated gene to reduce the expression of the over-amplified repeated sequence. The artificially manipulated gene includes one or more genes selected from the group consisting of an SPT4 gene, SPT5 gene, SUPT4H gene, and SUPT5H gene. The artificially manipulated gene includes an artificial mutation in a genomic sequence of the gene. The artificially manipulated gene includes a gene whose function is impaired or has reduced expression.