Gene Regulation and RNA Polymerase Isolation Mechanisms

Gene Regulation and Molecular Insights

Goal: To organize gene orientation and understand gene regulation involving 25,000 Protein-Coding Genes (PCG) and 40,000 non-coding RNA (ncRNA) to advance knowledge and medical insight.

Key Mechanisms of Gene Expression

• 3D Chromosome Territories: mRNA looping and open chromatin.
• Epigenetic Marks:
  • Little to no methylation on DNA.
  • Histone marks.
  • Chromatin modification coactivator complexes and ncRNA coactivators.
• Transcription Factor Activators: Usually heterodimers.
  • Transactivation Domain (TD): Interacts with the mediator.
  • Binding Domain (BD): Binds to DNA.
• RNA Polymerase and Factors at the Promoter:
  • Elongation process.
  • Production of multiple mRNA molecules.
  • Presence of many promoters.
• Maternal and Paternal Expression:
  • Dogmatic: 50/50 expression.
  • Dynamic: 100:0 or 0:100 expression.
• Processing of Pre-mRNA: Proper and timely processing in the nucleus, including alternative splicing, before mature mRNA is exported to the cytoplasm.
• Translation: mRNA is translated into proteins in the cytoplasm; one mRNA can produce multiple proteins.
• Protein vs. mRNA Levels: Approximately 40% to 60% are controlled by transcription or post-transcription.
• Protein Regulation: Proteins can upregulate or deregulate gene expression; 30% of proteins are regulated by kinases and phosphatases.

Cis-Regulatory Elements (CREs)

• Short-Range CREs: Promoter/Proximal Promoter (P/PP) — position and orientation dependent.
• Long-Range CREs:
  • Insulators: Position and bracket dependent genes.
  • LCR (Locus Control Region): Position and orientation dependent.
  • Enhancers: Position and orientation independent.

Isolating Eukaryotic RNA Polymerase

Evidence/Assay: To isolate eukaryotic RNA polymerase.

Hypothesis: It was hypothesized that multiple eukaryotic RNA polymerases exist.

Reagents and Assay: Initially, nuclear proteins were bound to positively charged beads using ion exchange chromatography at low salt concentrations. Investigators first attempted to isolate nuclear proteins with negative beads, but this failed, indicating that RNA polymerases are positively charged proteins. Subsequently, proteins were eluted off the beads using increasing salt concentrations. The proteins eluted in the order of A, B, C, D, and E. These isolated proteins were then incubated with ³²P-labeled DNA.

Results and Conclusions: All proteins bound, confirming they are net positive. The specific domain that binds to DNA must be negative. RNA polymerases were identified as follows: RNA Pol I corresponds to rRNA, RNA Pol II corresponds to mRNA, and RNA Pol III corresponds to tRNA. As salt concentration increased, more polymerase eluted off the beads.