Euchromatin is relaxed and transcriptionally active, while heterochromatin is condensed and transcriptionally repressed.
They are often regulated by posttranslational modification, such as phosphorylation, or by ligand binding, such as steroid hormones.
Specific transcription factors bind to specific promoter sequences called regulatory elements, which are essential for the initiation of transcription.
Binding to 5‘-UTRs is associated with inhibition of translation, while binding to 3‘-UTRs increases translation efficiency by enhancing mRNA stability.
Phosphorylation of eIF-2α leads to its inability to bind GTP, resulting in inhibition of translation initiation.
Examples include 5-fluorouracil and mercaptopurine, which directly inhibit the synthesis of dNTPs.
8-hydroxyquinoline is an antifungal transcription inhibitor.
Methylation of CpG islands, which produces 5-methylcytosine, is associated with repression of transcription and is involved in imprinting.
Inhibitors of replicative enzymes include inhibitors of topoisomerase, used to treat cancer or bacterial infections, and inhibitors of DNA polymerases, mainly used for antiviral treatments like acyclovir for herpes simplex.
Amanitin is a potent inhibitor of RNA polymerase 2 and is a deadly toxin found in several species of amanita mushrooms.
Specific inhibitors of prokaryotic translation can be used as powerful antibiotics for the treatment of bacterial infections.
The binding of initiation factors on CAP is essential for the initiation of translation, and their posttranslational modifications can change their binding properties and translation initiation rate.
Tissue-specific alternative splicing is the process where exons of RNA are joined in multiple ways during RNA splicing, resulting in different types of mRNA needed for specific cells or tissues.
Genes can be amplified or deleted, which are pathologic mechanisms associated with cancer development, such as amplification of the HER2 gene leading to breast cancer.
Streptomycin affects initiation and elongation at the 30S subunit.
The combination of all components is associated with comprehensive regulation of transcription in space and time.
Substrate analogues can be incorporated into DNA by DNA polymerases, inhibiting further replication. Examples include azidothymidine and cytosine arabinoside.
Drugs that damage DNA include alkylating agents (used in cancer treatment), platinum complexes (for solid tumors like breast cancer), and bleomycin (also for cancer treatment).
Enhancers increase the rate of transcription, while silencers decrease the rate of transcription.
Rifampicin is an antibacterial that inhibits prokaryotic DNA transcription by binding to the b-subunit of RNA polymerase.
Puromycin causes premature termination at the 70S and 80S ribosomes.
Histone acetylation leads to the production of ε-N-acetyl lysine, which relaxes chromatin and activates transcription.
The binding of specific proteins on the 3'-UTR or poly-A tail of mRNA significantly increases mRNA stability, leading to increased expression of particular proteins.
Intercalating agents are drugs that insert between DNA strands, disrupting or changing DNA conformation, which is associated with inhibition of replication. Many are mutagenic. Examples include anthracycline glycosides like daunorubicin and doxorubicin.
The three main mechanisms of targeted mRNA localization are direct transport of mRNA on the cytoskeleton, random diffusion of mRNA and trapping, and degradation of mRNA combined with local protection.
miRNAs bind to complementary sequences on target mRNAs, leading to quick elimination by ribonucleases and blocking translation elongation.
RNA editing involves altering the information stored in an mRNA through chemical modifications of bases, such as insertions or deletions of uracil and deamination of cytidine to uridine or adenine to inosine.
The most common inhibitors of translation are antibiotics and antimetabolites.
Erythromycin affects translocation at the 50S subunit.
Antimetabolites are chemical compounds that inhibit the use of a metabolite, often resembling the metabolite they interfere with. They inhibit the production of substrates necessary for DNA replication, leading to decreased substrate availability and a reduced rate of replication.
The transport of mRNA from the nucleus is crucial for gene expression regulation during development, as uneven distribution of synthesized proteins is fundamental for cell differentiation.
Diphtheria toxin affects elongation by inactivating eEF-2.
The most common mode of alternative splicing is exon skipping, where a particular exon may be included in mRNAs under certain conditions or in specific tissues.
