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CH 19: Transcriptional Regulation in Eukaryotes (B. Recruitment of Protein…
CH 19: Transcriptional Regulation in Eukaryotes
A. Conserved Mechanisms of Transcriptional Regulation from Yeast to Mammals
Activators have separate DNA-binding and activating functions
Eukaryotic regulators use a range of DNA-binding domains, but DNA recognition involves the same principles as found in bacteria
Homeodomain proteins, Zinc-containing DNA-binding domains, Leucine zipper motif, helix-loop-helix proteins, HMG proteins
Activating Regions are not well-defined structures
B. Recruitment of Protein Complexes to Genes by Eukaryotic Activators
Activators recruit the transcriptional machinery to the gene
Activators also recruit nucleosome modifiers that help the transcriptional machinery bind at the promoter or initiate transcription
Activators recruit additional factors needed for efficient initiation or elongation at some promoters
Action at a distance: Loops and insulators
Appropriate regulation of some groups of genes requires locus control regions
C. Signal Integration and Combinatorial Control
Activators work synergistically to integrate signals
Signal integration: the HO gene is controlled by two regulators - one recruits the nucleosome modifiers, and the other recruits mediator
Signal integration: cooperative binding of activators at the human β-Interferon gene
Combinatorial control lies at the heart of the complexity and diversity of eukaryotes
Combinatorial control of the mating-type genes from S. cerevisiae
D. Transcriptional Repressors
F. Gene "Silencing" by Modification of Histones and DNA
Silencing in yeast is mediated by deacetylation and methylation of histones
In drosophila, HP1 recognizes methylated histones and condenses chromatin
Repression by polycomb also uses histone methylation
DNA methylation is associated with silenced genes in mammalian cells
E. Signal Transduction and the Control of Transcriptional Regulators
Signals are often communicated to transcriptional regulators through signal transduction pathways
Signals control the activities of eukaryotic transcriptional regulators in a variety of ways
G. Epigenetic Gene Regulation
Some states of gene expression are inherited through cell division even when the initiating signal is no longer present