Gene repressor proteins which inhibit the transcription of particular genes in eukaryotes also exist. They may act by binding either to control parts within the promoter region near the gene or at sites located a long distance away from the gene, called 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. Furthermore, other repressors inhibit transcription by blocking activation. This can be get in one of several ways: by blocking the DNA binding site for an activator protein, through binding to and masking the activation domain of the activator factor, or by forming a non-DNA binding complex with the activator protein. Several instance of every mode of action are known.