What are the six ways in which eucaryotic gene repressor proteins operate?
1) gene activator proteins and gene repressor proteins compete for binding to the same regulatory DNA sequence
2) Both proteins can bind DNA, but the repressor binds to the activation domain of the activator protein, thereby preventing it from carrying out its activation functions. In a variation of this strategy, the repressor binds tightly to the activator without having to be bound to DNA directly
3) The repressor blocks assembly of the general TFs; some also act at late stages in transcription initiation by preventing the release of the RNA polymerase from the general transcription factors
4) The repressor recruits a chromatin remodeling complex which returns the nucleosomal state of the promoter region to its pre-transcriptional form
5) The repressor attracts a histone deacetylase to the promoter. Histone acetylation can stimulate transcription initiation and the repressor simply reverses this modification
6) the repressor attracts a histone methyl transferase which modifies certain positions on histones which, in turn, are bound by proteins that maintain the chromatin in a transcriptionally silent form