Chapter 8. Post-transcriptional controls.
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Transcription regulators control gene expression by what two methods?
Promoting or hindering the transcription of specific genes.
_______ ________ controls operate after transcription has begun to regulate the amount or activity of the gene products that they make.
What are the post-transcriptional controls.
- 1. Each mRNA controls its own degradation and translation.
- 2. Regulatory RNAs control the expression of thousands of genes.
- 3. MicroRNAs direct the destruction of target mRNAs.
- 4. Small interfering RNAs are produced from double stranded, foreign RNAs to protect cells from infections.
- 5. Long noncoding RNAs may regulate mammalian gene activity.
How does each mRNA control its own degradation and translation?
- 1. mRNA contains specific sequences upstream and downstream of the protein-coding sequence for proteins that are involved in RNA degradation.
- 2. Sequences in each mRNA that help control how often it will be translated into protein.
- 3. Block-or expose the ribosome-binding sequence by RNA-binding protein, the bacterium can either inhibit- or promote- the translation of an mRNA.
- 3.1. Presence of thermosensor RNA sequence exposing the ribosome binding sequence through warmer temperature.
- 4. Eukaryotic repressor proteins inhibit translation initiation by binding to 5' untranslated region of mRNA preventing ribosome from finding the first AUG but when conditions change, the cell can inactivate the repressor to initiate translation of the mRNA.
What do regulatory RNAs control or regulate and what is their important role?
What are the various types of regulatory RNAs?
- Expression of thousands of genes.
- Regulate the gene expression.
- 1. microRNAs
- 2. Small interfering RNAs
- 3. Long noncoding RNAs.
What do microRNAs direct or do?
How many nucleotides does miRNA have?
What is the specific process?
- Destruction of target mRNAs or reduce rate of translation of mRNA.
- Base-pair with specific mRNAs and reduce both their stability and their translation into protein regulating expression of 1/3 of protein-coding genes.
- 1. Double-stranded miRNA intermediate binds with (RNA-induced silencing complex) RISC proteins forming a complex.
- 2. RISC patrols the cytoplasm searching for mRNAs that has nucleotide sequences complementary to the bound miRNA molecule.
- 3. If there is extensive match, then the mRNA is rapidly degraded using nucleases and the RISC is released.
- 4. If there is less extensive match, the mRNA translation is reduced, mRNA sequestered and eventually degraded and RISC is released.
What is produced from double stranded, foreign RNAs to protect cells from infections.
What is RNA interference?
What is the specific process?
Small interfering RNAs.
It is the process by which the system is used to eliminate "foreign" RNA molecules- in particular, the double-stranded RNAs produced by many viruses and transposable genetic elements.
- 1. Double-stranded, foreign RNAs are cut into short fragments by a protein called Dicer.
- 2. The resulting double-stranded RNA fragments called small interfering RNAs are taken up by the same RISCs that carry miRNAs.
- 3. The RISC discards one strand of the siRNA duplex and uses the remaining single-stranded RNA to seek and destroy complementary foreign RNA molecules.
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