Eukaryotic Gene Transcription

RNA Polymerases in Eukaryotes

• RNA Polymerase I synthesizes precursor of mature rRNA.
• RNA Polymerase II transcribes nuclear precursors of mRNA.
• RNA Polymerase III synthesizes tRNA, 5S rRNA, and some snRNA and snoRNA.

Histone Modifications

• Acetylation of histones decreases their interaction with DNA, promoting transcriptional activation.
• Methylation of histones can promote or inhibit DNA interactions depending on the context.

Transcription Factors and Promoter Elements

• TATA-binding protein (TBP) recognizes and binds the TATA-box in eukaryotes.
• Proximal regulatory elements are consensus sequences within 200 nucleotides of the core promoter, crucial for transcription regulation.

Enhancers and Promoter Regions

• Enhancers are DNA elements that enhance transcription initiation by recruiting transcription factors.
• Promoter regions are essential for initiating transcription; they primarily recruit RNA polymerase and transcription factors.

Exons vs. Introns

• Exons are coding sequences within genes that are expressed in the final mRNA product.
• Introns are non-coding sequences that are spliced out during mRNA processing.

RNA in Prokaryotes

• RNA polymerase is the enzyme that synthesizes RNA from DNA in prokaryotes.
• Transcription factors play critical roles in regulating gene expression by facilitating or inhibiting RNA polymerase binding.

mRNA Characteristics

• Eukaryotic mRNAs undergo extensive post-transcriptional modifications, including capping, polyadenylation, and splicing.
• Prokaryotic mRNAs are typically polycistronic and do not undergo such modifications.

Peptide Bond Formation and Genetic Information Transfer

• Ribosomal RNA (rRNA) is responsible for forming peptide bonds during protein synthesis.
• Messenger RNA (mRNA) carries genetic information from DNA to ribosomes for translation.

RNA Processing

• Small nuclear ribonucleoprotein particles (snRNPs) facilitatespliceosome function during mRNA splicing.
• Small interfering RNAs (siRNAs) play a role in gene regulation by targeting mRNA for degradation.

Rho-Dependent and Rho-Independent Termination

• Rho protein is essential for rho-dependent transcription termination in prokaryotes, facilitating disengagement of RNA polymerase.
• Rho-independent termination involves the formation of a GC-rich hairpin loop structure in the RNA.

Posttranscriptional Modifications

• Eukaryotic rRNA undergoes modifications including methylation and pseudouridination during processing.
• tRNA undergoes trimming and the addition of CCA at the 3' end, crucial for its function.

5'-Cap Addition

• The addition of a 5'-cap to pre-mRNA enhances stability, facilitates nuclear export, and is critical for translation initiation.

Test your knowledge on eukaryotic gene transcription and the role of nuclear RNA pols. Explore the complexities of transcription in eukaryotes, including compartmentalization, different types of RNA pols for synthesizing rRNA, tRNA, and mRNA, the importance of transcription factors, and the unique promoter regions and chromatin involved in gene transcription.