Tiêu đề 24. TRANSCRIPTION AND TRANSCRIPTION FACTORS.pdf ✅

PHARMD GURU Page 2 c) TERMINATION:  Rho-Dependent Termination: Involves the Rho protein, which binds to a specific RNA sequence and moves toward RNA polymerase, causing transcription termination.  Rho-Independent Termination: The RNA transcript forms a hairpin loop followed by a poly-U tail, destabilizing the RNA-DNA hybrid and leading to polymerase dissociation. C. TRANSCRIPTION EFFICIENCY AND REGULATION:  Coupling with Translation: In prokaryotes, transcription and translation occur simultaneously.  Regulatory Mechanisms:  Sigma Factors: Allow RNA polymerase to recognize different promoters.  Operons: Clusters of functionally related genes controlled by a single promoter (e.g., lac operon). D. SIGNIFICANCE:  Rapid Adaptation: Enables quick responses to environmental changes.  Efficient Gene Regulation: Ensures coordinated expression of genes involved in related functions. 3. BASIC PRINCIPLES OF TRANSCRIPTION IN EUKARYOTES: A. OVERVIEW: Transcription in eukaryotes is highly regulated due to the presence of a nucleus and the complexity of chromatin structure. It involves multiple RNA polymerases, general transcription factors, and additional regulatory elements.
PHARMD GURU Page 3 Figure 1: Diagram illustrating the structure of RNA polymerase and its interaction B. STAGES OF TRANSCRIPTION IN EUKARYOTES: a) INITIATION:  RNA Polymerases:  RNA Polymerase I: Transcribes rRNA (except 5S rRNA).  RNA Polymerase II: Transcribes mRNA and small nuclear RNAs (snRNAs).  RNA Polymerase III: Transcribes tRNA, 5S rRNA, and other small RNAs.  Promoter Elements:  TATA Box: Located ~25-30 bp upstream of the transcription start site, recruits TATA-binding protein (TBP).  Initiator (Inr) Sequence: Surrounds the transcription start site, essential for transcription initiation.  Proximal Promoter Elements (CAAT box, GC box): Help regulate transcription efficiency.  Pre-Initiation Complex (PIC): A multi-protein complex involving TFIID, TFIIA, TFIIB, TFIIE, TFIIF, and TFIIH, which stabilizes RNA polymerase II at the promoter.