LIFESCI 3 Chapter 21.3: 21.3
Document Summary
Using multiple transcription factors to control genes requires dispersed binding sites. Dna looping accommodates large distances between enhancers and promoters. Insulators: dna sequences that form boundaries between genes or groups of genes. Can prevent genes from packing into heterochromatin. Has a repressive effect if located between promoter and enhancer. Insulators in higher eukaryotes require ctc-binding factor (ctcf) to function. Ctcf binds to a site containing a 5"-ccctc sequence. Enhanceosome: cooperating activators form stable tightly folded nucleoprotein complex. Integrates regulatory information from multiple signaling cascades and generates a single transcriptional outcome at the target promoter. Interferons are produced in response to viral infection and lead to programmed cell death halt production of viral particles and infection of surrounding cells. At the interferon beta promoter, multiple activators can interact with the cofactor protein complex cbp-p300. All activators in the enhanceosome must be present to be most efficient. Similar activator clusters can function together to repress transcription.
