Chapter 21 Flashcards
The condensed, heavily staining portions of chromosomes that are not transcriptionally active, including centromeres, telomeres, some repetitive DNA sequences, and mitotic chromosomes.
heterochromatin
The inherent activity of promoters and transcription machinery in vivo in the absence of regulatory mechanisms.
transcriptional ground state
The regions of interphase chromosomes that stain diffusely, as opposed to the more condensed, heavily staining, heterochromatin. These are often regions in which genes are being actively expressed.
euchromatin
The use of specific combinations of a limited number of regulatory proteins to exert fine control over gene expression.
combinatorial control
A DNA sequence that facilitates the expression of a given gene; it may be located a few hundred, or even thousand, base pairs away from the gene. In yeast, enhancers are called upstream activator sequences (UASs).
enhancer
A regulatory sequence in yeast DNA to which transcription activators bind.
upstream activator sequence (UAS):
In eukaryotic cells, a protein required at every Pol II promoter. Also called a basal transcription factor.
general transcription factor
In eukaryotic cells, a protein that binds to enhancers or UASs to facilitate transcription. Also called a DNA-binding transactivator.
DNA-binding transcription activator:
A protein that stimulates transcription by binding both the RNA polymerase and an activator or activators, without binding the DNA directly. Compare corepressor and DNA-binding transcription activator.
coactivator
Three families of chromosomal proteins that bind DNA nonspecifically, promoting chromatin remodeling and DNA looping for regulating DNA transcription.
high-mobility group (HMG) proteins:
A large, multiprotein complex in eukaryotic cells that serves as the mediator between the Pol II transcription complex and any upstream transcription activators or enhancers regulating Pol II–catalyzed transcription.
Mediator complex:
A protein complex with ATPase activity that translocates nucleosomes along the DNA, making certain regions of DNA more or less accessible to transcription factors
chromatin remodeling complex:
A short sequence of DNA that prevents inappropriate cross-signaling between regulatory elements for different genes. Also called a boundary element.
insulator
