Repetitive DNA regulates gene expression

Short tandem repeats affect gene expression by binding regulatory proteins Approximately 5% of the human genome consists of short tandem repeats (STRs), sequences in which repeating units of 1 to 6 base pairs form an array of up to 100 base pairs long ( 1 , 2 ). Variations in STR length are associated with, and often the causative agents of, gene expression changes present in some hereditary conditions, for example, Huntington's disease, autism, and schizophrenia ( 3 – 5 ). However, the mechanisms through which STRs exert their effects on gene expression remain poorly understood. On page 1304 of this issue, Horton et al. ( 6 ) demonstrate that STRs exert their effects by directly binding transcription factor proteins, thus explaining how STRs might influence gene expression in both normal and diseased states.