BIS 2A Lecture Notes - Proteasome, Conformational Change, Microrna
8 Jun 2018
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Eukaryotic Gene Regulation
• Structural differences between prokaryotic and eukaryotic gene regulation
o Eukaryotes have nucleus and DNA must be packaged and organized into
chromatin
▪ Transcriptional regulation occurs because tight packaging prevents access
to genes for transcription while loose packing allows transcription
o Involves strong/weak promoters, transcription factors, terminators but greater
number of proteins involved
o mRNA processing also adds level of transcription regulation because certain
exons are transported into the cytosol and other are not
• DNA packaging and epigenetic markers
o DNA winding around histone proteins to form nucleosomes
o Can move along the strand and control which regions of DNA are accessible for
transcription
o Histone modification
▪ Movement of histones depends on chemical interactions between
histones and DNA
▪ Epigenetic changes: regulation of gene expression through chromatin
remodeling
• Not permanent but temporarily close or open certain regions of
DNA
• Addition of phosphate, methyl, and acetate groups that change
how tightly DNA wound around the histone
• DNA negatively charged so tighter when histones have positive
charge
o Unmodified histones have positive charge but modified
ones have less positive charge
o Methylation causes tight packaging while acetylation
causes loose packaging
• Mutations within the DNA can prevent certain chemical
interactions between the histones and DNA and therefore affect
gene expression
o DNA modification
▪ Regions with high frequency of CG causes highly methylated DNA
• Methylated DNA and deacetylated histones tightly coiled and
transcription does not occur
• Eukaryotic gene structure and RNA processing
o Eukaryotic genes contain promoter, terminator, enhancers and silencers that
recruit transcription factors
▪ Enhancers allow interaction between activators and transcription factors
to occur
▪ Silencers repress gene expression or transcription
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