Introduction
Gene expression in eukaryotes is more complicated than in prokaryotes. The nuclear envelop makes it necessary for mRNA to be exported into cytoplasmic compartment, the gene regulation can occur at multiple levels: transcription, exportation, translation and post-translation.
Eukaryotic genes
Eukaryotic genes usually contain three basic regulatory components: enhancers, which are short regions of DNA that can be bound with proteins to promote expression of a distal or a proximal gene. Promoters which are proximal DNA sequences that binds to RNA polymerase for regulating gene expression. And TATA Box, which Binds to transcription factor for regulating gene expression, usually within 30bp of the transcription start site. Transcriptional control is all about how these elements interact with transcriptional machinery, transcriptional factors and co-factors.
Transcriptional control
Transcriptional control is regulated by basal transcription factors and regulatory transcription factors. Basal transcription factors bind to DNA and form basal transcription machinery including TFIIA, B, D, F and RNA polymerase II, they are required for transcription. Modulatory transcription factors regulate time/space differential expression. This includes 4 types: activator, co-activator, repressor and co-repressor.
Post-transcriptional control
Post-transcriptional control includes mainly splicing, 5’ capping, 3’ polyadenylation. In addition, mRNA sequestration and exportation also play roles in some genes. mRNA stability is known to be different for different genes, more and more evidence indicate that a large collection of small RNA molecules can regulate the mRNA stability in cells.
Control at protein level
This includes both translational control (i.e, when and where a protein is synthesized and how fast it is synthesized) and post-translational control (where the protein is going in or out of cell, what kind of modification it is required for activation/inactivation, etc). Translational control is largely achieved at translation initiation involving both cap-dependent and –independent mechanisms. Post-translational control includes modification such as phosphorylation, acetylation, methylation, protein folding and sorting.
