Regulation of Gene Expression
Gene expression is a highly complex, regulated process that begins with DNA transcribed into RNA, which is then translated into protein.
Prokaryotic versus Eukaryotic Gene Expression
Prokaryotes regulate gene expression by controlling the amount of transcription, whereas eukaryotic control is much more complex.
Prokaryotic Gene Regulation
The trp Operon: A Repressor Operon
The trp operon is a repressor operon that is either activated or repressed based on the levels of tryptophan in the environment.
Catabolite Activator Protein (CAP): An Activator Regulator
when glucose levels decline in
catabolite activator protein (CAP) is bound by cAMP to promote transcription of the lac operon.
The lac Operon: An Inducer Operon
The lac operon is an inducible operon that utilizes lactose as an energy source and is activated when glucose is low and lactose is present.
Eukaryotic Transcription Gene Regulation
The Promoter and the Transcription Machinery
When transcription factors bind to the promoter region, RNA polymerase is placed in an orientation that allows transcription to begin.
Transcriptional Enhancers and Repressors
Enhancers increase the rate of transcription of genes, while repressors decrease the rate of transcription.
Eukaryotic Epigenetic Gene Regulation
Epigenetic Control: Regulating Access to Genes within the Chromosome
Both the packaging of DNA around histone proteins, as well as chemical modifications to the DNA or proteins, can alter gene expression.
Eukaryotic Post-transcriptional Gene Regulation
RNA splicing allows for the production of multiple protein isoforms from a single gene by removing introns and combining different exons.
Eukaryotic Translational and Post-translational Gene
The Initiation Complex and Translation Rate
The first step of translation is the formation of an initiation complex (mRNA, ribosomes, tRNA) that requires additional initiation factors.
Chemical Modifications, Protein Activity, and Longevity
A cell can rapidly change the levels of proteins in response to the environment by adding specific chemical groups to alter gene regulation.
Development on the Cellular Level
Adding cells through cellular division
Symmetric division maintains stem cell lines and asymmetric division yields differentiated cells.
Differentiating cells to serve different functions
Cellular differentiation occurs so cells can specialize for different functions within an organism.
Mechanics of differentation: induction and gene expression
Cellular differentiation, a necessary process in development and maintenance of multicellularity, is regulated by transcription factors.
Establishing the body axes and patterns
Animal bodies have three axes for symmetry (lateral-medial, dorsal-ventral and anterior-posterior) which are established in development.
Cell migration is necessary for development and maintenance of multicellularity, and occurs through varying mechanisms.
Genes provide positional information
During development it is critical that specific gene expression patterns are established to signal and differentiate the cells appropriately.
Programmed cell death
Programmed cell death describes the death of a cell through a highly regulated process, and serves many functions in an organism.
Cancer and Gene Regulation
Cancer: Disease of Altered Gene Expression
Cancer, a disease of altered gene expression, is the result of gene mutations or dramatic changes in gene regulation.
Cancer and Epigenetic Alterations
Common in cancer cells, silencing genes, which occur through epigenetic mechanisms, include modifications to histone proteins and DNA.
Cancer and Transcriptional Control
Increased transcriptional activation of genes result in alterations of cell growth leading to abnormal gene expression, as seen in cancer.
Cancer and Post-transcriptional Control
Modifications, such as the overexpression of miRNAs, in the post-transcriptional control of a gene can result in cancer.
Cancer, Translational/Post-translational Control, and Targeted Therapies
Cancer can arise from translational or post-translational modifications of proteins.