Ch 7 Cont Section 5 - Control Of Gene Expression In Eukaryotes Flashcards
Transcription factors
Transcription activating proteins that search the DNA looking for specific DNA binding motifs. Tend to have two recognizable domains: a DNA binding domain and an activation domain.
DNA binding domain
Binds to specific nucleotide sequence in the promoter region or to a DNA response element (sequence of DNA that binds only to specific transcription factors) to help in the recruitment of transcriptional machinery.
Activation domain
Allows for binding of several transcription factors and other important regulatory proteins such as RNA polymerase and histone acetylases which function in the remodeling of the chromatin structure
Gene amplification.
Expression is increased in response to specific signals such as hormones, growth factors and other intercellular conditions. Accomplished through enhancers and gene duplication.
Enhancer
Several response elements grouped together. Allows for the control of one gene’s expression by multiple signals
Heterochromatin
Tightly coiled DNA inaccessible to the transcription machinery so these genes are inactive
Euchromatin
Loose chromatin - transcription machinery can access so this is active
Histone acetylases
Coactivators - these proteins are involved in chromatin remodeling - they acetylate lysine residues found in the amino terminal tail regions of histone proteins
Acetylation of histone proteins
Decreases positive charge on lysine residues and weakens interaction if histone with dna resulting in open chromatin conformation that allows for easier access of transcriptional machinery to dna
Histone deacetylases
Proteins that function to remove acetyl groups from histones which results in closed chromatin conformation and overall decrease in gene expression levels in the cell (gene silencing)
DNA methylation
Involved in chromatin remodeling and regulation of gene expression levels in the cell - dna methylases add methyl groups to cytosine and adenine nucleotides; methylation linked with silencing genes which no longer need to be activated. Heterochromatin much more easily methylated