Tahapan Transkripsi RNA pada Eukariotik

Summary

This video explores the transcription process in eukaryotes, highlighting the key differences from prokaryotic transcription. It explains the role of transcription units, enzymes, and promoters in both types of organisms. In prokaryotes, one transcription unit may consist of several genes, while in eukaryotes, it typically represents a single gene. Eukaryotic transcription involves multiple RNA polymerases and basic transcription factors, unlike prokaryotes where RNA polymerase can directly attach to DNA. Additionally, eukaryotes modify the mRNA by adding a methyl guanosine cap and a poly-A tail, offering protection and aiding translation. The video also touches on RNA editing in eukaryotes.

Takeaways

• 😀 Prokaryotic transcription units can contain several adjacent genes, while eukaryotic transcription units generally consist of a single gene.
• 😀 In prokaryotes, transcription is carried out by a single type of RNA polymerase, while eukaryotes have at least five different RNA polymerases, each transcribing different genes.
• 😀 Eukaryotic promoters are more complex than prokaryotic promoters, featuring additional consensus regions like the TATA box, GC boxes, and the CAAT box.
• 😀 In prokaryotes, RNA polymerase directly binds to the promoter region, but in eukaryotes, several basic transcription factors must first attach to the promoter before RNA polymerase can bind.
• 😀 The initiation process in eukaryotic transcription involves a series of steps, starting with the binding of TF2D to the TATA box, followed by other transcription factors and RNA polymerase II.
• 😀 In eukaryotes, the 5' end of the synthesized RNA is capped with a methyl guanosine cap (7mG), which protects the RNA from degradation and aids in translation initiation.
• 😀 Prokaryotic transcription ends with the formation of a hairpin structure in the RNA, whereas in eukaryotes, transcription termination involves the cutting of the RNA and the addition of a poly-A tail to the 3' end.
• 😀 The addition of the poly-A tail in eukaryotes enhances RNA stability and helps direct the RNA for translation in the cytoplasm.
• 😀 Eukaryotic mRNA can undergo RNA editing, where sequences within the mRNA are altered, potentially affecting the resulting protein. This is evident in apolipoprotein gene expression.
• 😀 A major difference between prokaryotic and eukaryotic transcription is that eukaryotic transcription is more complex, requiring various transcription factors and additional RNA processing steps such as capping and polyadenylation.

Q & A

What is a transcription unit in prokaryotes?

In prokaryotes, a transcription unit can consist of multiple genes, meaning that a single transcription unit can transcribe several adjacent genes into RNA.

How does the transcription unit in eukaryotes differ from prokaryotes?

In eukaryotes, the transcription unit generally consists of one gene, meaning one transcription unit corresponds to one gene, unlike prokaryotes where multiple genes can be transcribed together.

What is the role of RNA polymerase in prokaryotic transcription?

In prokaryotes, a single type of RNA polymerase is responsible for transcribing various genes throughout the prokaryotic genome.

How many types of RNA polymerase exist in eukaryotes, and what is their function?

Eukaryotes have at least five types of RNA polymerases (I, II, III, IV, and V), each responsible for transcribing different sets of genes.

What are the key features of the prokaryotic promoter?

The prokaryotic promoter is relatively simple, consisting of two consensus regions: the -10 region and the -35 region. These regions help RNA polymerase recognize and initiate transcription.

What are the key differences in promoter regions between prokaryotes and eukaryotes?

Eukaryotic promoters are more complex than prokaryotic ones. They include elements such as the TATA box (found about 20 nucleotides upstream of the transcription start) and other regions like the GC box and the octamer box.

What are basal transcription factors in eukaryotes, and why are they important?

Basal transcription factors are a set of proteins in eukaryotes that are required for RNA polymerase to bind to the promoter and initiate transcription. They help form a complex that enables RNA polymerase to start the transcription process.

What happens during the elongation stage of transcription in both prokaryotes and eukaryotes?

During elongation, RNA polymerase adds nucleotides to the growing RNA strand at the 3' end, using one of the DNA strands as a template. The process is essentially the same in both prokaryotes and eukaryotes.

What is the 5' methylguanosine cap, and why is it important in eukaryotic transcription?

The 5' methylguanosine cap is added to the 5' end of the RNA molecule in eukaryotes. It protects the RNA from degradation by nucleases and also facilitates its interaction with translation initiation factors, aiding in the translation process.

How does transcription termination differ between prokaryotes and eukaryotes?

In prokaryotes, termination occurs when a hairpin structure forms in the RNA, causing RNA polymerase to detach. In eukaryotes, termination involves the cleavage of the RNA at a specific site, followed by the addition of a poly-A tail at the 3' end, a process called polyadenylation.

What is polyadenylation, and what is its function in eukaryotic transcription?

Polyadenylation is the addition of a long adenine base chain (poly-A tail) to the 3' end of the RNA in eukaryotes. It helps protect the RNA from degradation, stabilizes it, and assists in the transport of RNA from the nucleus to the cytoplasm.

What is RNA editing, and how does it affect gene expression in eukaryotes?

RNA editing is a process where the RNA sequence is altered after transcription, affecting the resulting protein. For example, in apolipoprotein genes, RNA editing in different tissues can result in proteins of different lengths, as seen with the apolipoproteins in the liver and intestine.