Repressors:

Gene repressor proteins which inhibit the transcription of specific genes in eukaryotes also exist. They may act through binding either to control parts within the promoter region near the gene or at sites located a long distance away from the gene, known as silencers.  The repressor protein should inhibit transcription directly. One instance is the mammalian thyroid hormone receptor that,in the absence of thyroid hormone represses transcription of the goal genes. Moreover, other repressors inhibit transcription through blocking activation. This can be get  in one of various ways: through blocking the DNA binding site for an activator protein, through binding to and masking  the activation domain of the activator factor, or through  forming a non-DNA binding  complex  with  the activator protein. Various instance of every mode of action are known.