The Transcription termination factor (Ttf1, also known as Ttf-1 and Ttf-I) binds the Sal box element in the intergenic regions of rRNA genes (Grummt et al. 1986, Evers and Grummt 1995). Affinity of Ttf1 for Sal box DNA is about 0.1X the affinity of other transcription factors, such as the A and B isoforms of human MAX, for their binding sites (Diermeier et al. 2013). Ttf1 cooperatively binds Sal box chromatin and forms oligomers that organize rDNA repeats into loops (Diermeier et al. 2013). Ttf1 participates in pausing transcription and in epigenetic regulation of rRNA transcription (Diermeier et al. 2013). Interactions with other proteins such as Tip5 influence the DNA-binding activity of Ttf1 (Nemeth et al. 2004).