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EUKARYOTIC GENE REGULATION, SANDHYA A 191822016 - Coggle Diagram
EUKARYOTIC GENE REGULATION
DEFINITION
Gene regulation is the process of controlling which genes in a cell's DNA are expressed (used to make a functional product such as a protein).
EXPRESSION PATTERN
INSIDE THE CELL
the proteins it inherited from its mother cell, whether its DNA is damaged, and how much ATP it has.
OUTSIDE THE CELL
chemical signals from other cells, mechanical signals from the extracellular matrix, and nutrient levels.
STEPS/STAGES
Chromatin accessibility
The structure of chromatin (DNA and its organizing proteins) can be regulated. More open or “relaxed” chromatin makes a gene more available for transcription.
Transcription
Transcription is a key regulatory point for many genes. Sets of transcription factor proteins bind to specific DNA sequences in or near a gene and promote or repress its transcription into an RNA.
RNA processing
Splicing, capping, and addition of a poly-A tail to an RNA molecule can be regulated, and so can exit from the nucleus. Different mRNAs may be made from the same pre-mRNA by alternative splicing.
RNA stability. RNA stability.
The lifetime of an mRNA molecule in the cytosol affects how many proteins can be made from it. Small regulatory RNAs called miRNAs can bind to target mRNAs and cause them to be chopped up.
Protein activity.
Proteins can undergo a variety of modifications, such as being chopped up or tagged with chemical groups. These modifications can be regulated and may affect the activity or behavior of the protein.
Translation
Translation of an mRNA may be increased or inhibited by regulators. For instance, miRNAs sometimes block translation of their target mRNAs (rather than causing them to be chopped up).
TRANSCRIPTION FACTORS
Activators
Some transcription factors activate transcription. For instance, they may help the general transcription factors and/or RNA polymerase bind to the promoter,
Binding sites
The binding sites for transcription factors are often close to a gene's promoter. However, they can also be found in other parts of the DNA, sometimes very far away from the promoter, and still affect transcription of the gene.
REGULATION OF RNA PROCESSING
Alternative splicing
Most pre-mRNA molecules have sections that are removed from the molecule, called introns, and sections that are linked or together to make the final mRNA, called exons. This process is called splicing.
Small regulatory RNAs
Once an mRNA has left the nucleus, it may or may not be translated many times to make proteins. Two key determinants of how much protein is made from an mRNA are its "lifespan" (how long it floats around in the cytosol) and how readily the translation machinery, such as the ribosome, can attach to it.
microRNAs
microRNAs (miRNAs) were among the first small regulatory RNAs to be discovered. A miRNA is first transcribed as a long RNA molecule, which forms base pairs with itself and folds over to make a hairpin.
LATER STAGES
RNA processing, such as splicing, capping, and poly-A tail addition
Messenger RNA (mRNA) translation and lifetime in the cytosol
Protein modifications, such as addition of chemical groups
REGULATION OF TRANSLATION
In order for translation to begin, the ribosome, an RNA-and-protein complex that houses translation, must assemble on the mRNA. This process involves many “helper” proteins, which make sure the ribosome is correctly positioned. Translation can be regulated globally (for every mRNA in the cell) through changes in the availability or activity of the “helper” proteins.
SANDHYA A 191822016