eukaryotic vs prokaryotic gene regulation

Gene Regulation Components

  • Regulation occurs at multiple levels:
    • Chromosome
    • Transcription
    • mRNA
    • Translation
    • Protein itself
  • These regulations fine-tune protein production to meet cellular goals.

Chromosome Level Regulation

  • During mitosis, chromosomes condense tightly for separation.
  • Chromosomal remodeling can alter DNA packing before transcription.
  • Epigenetics: Chemical modifications, like adding a methyl group to cytosine (C), affect gene expression.
    • Methylation often occurs at CG doublets.
    • It is associated with decreased gene expression by silencing.

Transcriptional Regulation

  • DNA uses enhancers, silencers, and regulatory proteins (activators or repressors) to control gene transcription.
  • Alternate promoters can create variations in the 5' UTRs, influencing the resulting protein.

Post-Transcriptional Regulation

  • Alternative splicing of mRNA produces different final products.
  • RNA-mediated regulation involves mRNA degradation rates affected by the 5' UTR.
  • Double-stranded RNAs can promote degradation or block translation.
  • Non-coding RNAs (microRNAs, small interfering RNAs, antisense RNAs) regulate mRNA stability and translation in eukaryotes.
  • Regulatory RNAs are produced from regions of the genome that may not encode structural genes.

Chromatin Remodeling

  • Involves repositioning or removing nucleosomes on DNA.
  • This makes chromosomal regions accessible to regulatory proteins and RNA polymerase II.
  • Nucleosomes can be repositioned, removed, or exchanged with histone variants to allow transcription.
  • CPG refers to cytosine and guanine bases next to each other on the same DNA strand, where methylation frequently occurs.

Methylation

  • Identical twins exhibit different methylation patterns due to lived experiences, demonstrating epigenetic effects.
  • Post-traumatic stress disorder (PTSD) is linked to DNA methylation patterns affecting the immune system and cellular defense mechanisms.
  • DNA methylation is associated with decreased gene expression.

Transcriptional Regulation Comparison: Prokaryotes vs. Eukaryotes

  • Focus is on comparing lac operon (prokaryotes) with eukaryotic gene regulation.

Prokaryotes (Bacteria)

  • Promoters in bacteria organize multiple genes under a single promoter and operator (operons).
  • Operons allow efficient regulation of multiple genes simultaneously on a single bacterial chromosome.
  • RNA polymerase transcribes the operon into a single mRNA containing several structural genes (e.g., lacZ, lacY, lacA).