Tiêu đề 23. GENE EXPRESSION.pdf ✅

PHARMD GURU Page 3 environmental stimuli. A. KEY GENETIC ELEMENTS: 1. PROMOTERS:  Definition: DNA sequences located upstream of genes that serve as binding sites for RNA polymerase and transcription factors.  Types:  Core Promoter: Includes essential elements like the TATA box and initiator (Inr) sequence.  Proximal Promoter Elements: Located upstream of the core promoter, enhancing transcription factor binding.  Function: Determines the rate of transcription initiation and gene expression levels. 2. ENHANCERS:  Definition: DNA sequences that increase transcription rates by binding activator proteins.  Mechanism: Facilitates DNA looping, bringing transcription factors close to the promoter region.  Example: Immunoglobulin heavy chain enhancer is essential for high-level transcription in B cells. 3. SILENCERS:  Definition: DNA sequences that suppress gene expression by binding repressor proteins.  Function: Prevents unnecessary gene expression, ensuring tissue-specific gene regulation.  Example: NRSE/RE1 silencer represses neuronal genes in non-neuronal tissues. 4. INSULATORS:  Definition: Boundary elements that block interactions between enhancers and promoters of unintended genes.