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Polyadenylation occurs at the 3' end (the back) of an mRNA strand in the nucleus of the cell. This act of polyadenylation creates a polyadenine (polyA) tail. mRNA cannot leave the nucleus of the cell unless polyadenylation occurs.
PolyA tails seem to protect integrity of the mRNA molecule, which is exposed to multiple proteins that can degrade it once shipped to the cytoplasm
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What is polyadenylation mechanism?
Polyadenylation is a process in which a poly(A) tail is added to the 3' end of a newly synthesized mRNA molecule. This poly(A) tail helps to stabilize the mRNA molecule and plays a role in the export of the mRNA from the nucleus to the cytoplasm for translation. Polyadenylation also signals the termination of transcription.
Where does polyadenylation take place?
Polyadenylation takes place in the cell nucleus after a pre-mRNA molecule has been transcribed but before it is processed into a mature mRNA molecule. During polyadenylation, a string of adenine nucleotides, known as a poly(A) tail, is added to the 3' end of the pre-mRNA.
What is the polyadenylation mechanism?
Polyadenylation is a process in which a string of adenine nucleotides is added to the 3' end of a newly synthesized mRNA molecule. This poly(A) tail plays a crucial role in mRNA stability and regulation, as well as in the process of protein translation. The polyadenylation mechanism is mediated by several proteins that recognize specific sequences on the mRNA molecule and facilitate the addition of the poly(A) tail.
What is the functional connection between polyadenylation and transcriptional termination of pol II transcription?
Polyadenylation and transcriptional termination of RNA polymerase II (Pol II) are closely linked processes in eukaryotic gene expression. After the transcription of a gene, the addition of a poly(A) tail to the 3' end of the mRNA helps stabilize the transcript and signals for termination of transcription. The polyadenylation signal in the RNA sequence triggers the recruitment of specific cleavage and polyadenylation factors, which facilitate the cleavage of the nascent RNA and the release of the Pol II enzyme, effectively terminating transcription. This coordinated action ensures proper mRNA maturation and gene regulation.
What is mRNA processing?
mRNA processing is a series of modifications that occur to a primary RNA transcript (pre-mRNA) before it is translated into a protein. This process includes capping, splicing, and polyadenylation to produce a mature mRNA molecule that can be effectively translated in the cell.
What happens before messenger RNA is mature?
Before messenger RNA (mRNA) is mature, it undergoes several post-transcriptional modifications. These modifications include capping, splicing, and polyadenylation. Capping involves adding a modified guanine nucleotide at the 5' end, splicing removes introns to create a mature mRNA sequence, and polyadenylation adds a poly-A tail at the 3' end.
What happens to mRNA when it leaves a ribosome?
Once mRNA leaves a ribosome, it can be degraded by cellular enzymes or recycled for further rounds of translation. It may also undergo additional modifications, such as polyadenylation, to stabilize or target it for degradation. Ultimately, the fate of mRNA depends on various factors within the cell.
What are the three main ways through which an mRNA strand is modified between transcription and translation?
The three main ways mRNA strand is modified are 5' capping, 3' polyadenylation, and RNA splicing. 5' capping involves adding a modified nucleotide at the 5' end to protect the mRNA from degradation. 3' polyadenylation involves adding a string of adenine nucleotides at the 3' end to stabilize the mRNA and regulate its translation. RNA splicing is the removal of non-coding regions (introns) and joining of coding regions (exons) to form a mature mRNA molecule.
What is the purpose of polyadenylation of mRNA of the nucleus?
Polyadenylation of mRNA in the nucleus serves several key purposes: it adds a long stretch of adenine nucleotides (the poly(A) tail) to the 3' end of the mRNA transcript, which enhances mRNA stability and protects it from degradation. This modification also plays a crucial role in the regulation of nuclear export, facilitating the transport of mature mRNA to the cytoplasm. Additionally, the poly(A) tail is important for efficient translation of the mRNA into protein by aiding in the initiation of translation.
What happens right after the end of transcription?
After transcription, the mRNA produced is modified through processes like capping and polyadenylation. This modified mRNA then leaves the nucleus and enters the cytoplasm where it can be translated into a protein by ribosomes.
What activity must mRNA do in traveling from DNA to protein synthesis sites in eukaryootic cells that does NOT occur in prokaryotic cells?
In eukaryotic cells, mRNA must undergo processing, which includes capping, polyadenylation, and splicing, before it can be transported from the nucleus to the cytoplasm for protein synthesis. This processing is essential for stability and translation efficiency. In contrast, prokaryotic cells do not have a nucleus, and their mRNA is translated directly after transcription without such modifications.
Why is protein synthesis different in pakaryotes and eukaryotes?
Protein synthesis differs in prokaryotes and eukaryotes primarily due to cellular structure and compartmentalization. In prokaryotes, transcription and translation occur simultaneously in the cytoplasm since they lack a defined nucleus. In contrast, eukaryotes have a nucleus where transcription occurs, followed by RNA processing before translation takes place in the cytoplasm. Additionally, eukaryotic mRNA undergoes modifications like capping and polyadenylation, which are not present in prokaryotic mRNA.
