Gene Expression and Structure in Eukaryotes Part II-C (Exam 2)

Motivational Quote

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Gene Expression in Eukaryotes

• Eukaryotic gene expression differs significantly from prokaryotic gene expression
• Eukaryotic gene expression involves a multistep process
• The location of mRNA production and translation differ between eukaryotes and prokaryotes
• Eukaryotic mRNA maturation involves steps: splicing, capping and addition of a poly(A) tail.

Prokaryotic vs. Eukaryotic Gene Structure

• Prokaryotic genes are typically organized into operons, while eukaryotic genes are not.
• Eukaryotic genes contain introns, which are removed during mRNA processing, but prokaryotic genes do not contain introns.
• Eukaryotic genes have a more complex structure with multiple regulatory sequences located both upstream and downstream of the protein coding region

Structure of Eukaryotic Gene (dsDNA)

• Eukaryotic genes have several distinct elements that regulate start and stop transcription
• Promoter regions consist of core promoters (e.g. TATA box, CAAT box, GC box) and proximal and distal promoters.
• Insulators are proteins that regulate gene expression at a distance
• Enhancers increase transcription initiation and silencers decrease it

More on Eukaryotic Promoters

• Active promoters are often in nucleosome-free zones.
• Epigenetic marks can affect promoter activity.
• Promoters can be bivalent or poised during development, changing activity as cells differentiate
• Some genes have multiple alternate promoters that can respond to different regulatory elements.

Enhancers

• Enhancers are regulatory elements that can increase transcription initiation
• Enhancers are recognized and bound by tissue-specific transcription factors.
• Enhancers play a crucial role in coordinating gene expression patterns in different tissues

Eukaryotic Transcription Termination

• Cleavage and polyadenylation specificity factor (CPSF) and PolyA Polymerase (PAP) are involved in termination

Alternative Splicing

• Alternative splicing produces different protein isoforms from a single gene.
• Alternative splicing allows for greater diversity in the proteins produced by a single gene

38,016 Shades of DSCAM

• Drosophila has an unusual gene allowing for many different protein products.
• The DSCAM gene produces a high diversity of mRNA and proteins due to alternative exon usage
• The large number of protein variations is due to mutual exclusive exons

Prokaryote vs Eukaryote mRNA

• Prokaryotic mRNA is polycistronic, encoding multiple proteins from a single mRNA molecule, while eukaryotic mRNA is monocistronic, encoding a single protein.
• Eukaryotic mRNA has a 5' cap and 3' poly(A) tail, protecting it from degradation and enhancing its translation, which are absent in prokaryotic mRNA.

Eukaryotic Translation

• Eukaryotic translation uses a more complex machinery compared to prokaryotic translation.
• Eukaryotic ribosomes are larger.
• Eukaryotic translation is initiated at certain factors.

Flow of Genetic Information

• Process of gene expression: DNA to mRNA to protein
• Includes steps like transcription and translation

mRNA Processing

• mRNA processing is crucial for generating functional mRNA
• Steps include capping, splicing and polyadenylation

Eukaryotic Gene Expression: Regulation

• Eukaryotic gene expression is regulated at the transcriptional level
• Regulation includes factors like internal cellular signals, DNA binding factors, chromatin state, transcription machinery, and other external factors.
• Housekeeping genes are expressed in all cells.
• Other genes have special expression patterns.

Translation: Prokaryotes vs. Eukaryotes

• The differences in the process of translating mRNA between prokaryotes and eukaryotes
• Includes differences in ribosome structure, locations, and mRNA life cycle characteristics

5' Cap

• 7-methylguanosine is a modification made to the 5' end of mRNA
• Plays a vital role in protecting mRNA and initiates translation

Cap-and Poly(A) binding Proteins

• These proteins bind to caps and tails and facilitate interaction with eukaryotic ribosomes

Prokaryotic Gene Structure

• Prokaryotic genes (often in operons) have promoters, RNA coding regions and terminators

Eukaryotic Gene Structure

• Eukaryotic gene structure is more complex with specific regions including promoters, introns, exons, and other regulatory sequences.
• Includes both upstream and downstream control elements

Structure of Eukaryotic Gene

• The structure of a eukaryotic gene showing components that help regulate transcription rate and other crucial regions during mRNA processing and the translation process.

Eukaryotic Transcription is Complex

• Describes the intricate process of transcription in eukaryotic cells
• Explains how different factors and elements influence RNA production and processing

Eukaryotic Translation Mechanism

• Describes the actions of factors throughout the translation process