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DNA Transcription Process in Prokaryotes

Jun 24, 2024

DNA Transcription Process in Prokaryotes

Introduction

  • Focus of the series: DNA transcription process
  • Other related topics: DNA replication, protein synthesis (translation)
  • Transcript focus: DNA transcription in prokaryotes
    • DNA transcription in eukaryotes covered in other videos
  • Transcription is part of the central dogma of biology
    • Information transfer from DNA (master) to functional RNA --> proteins
  • Goal: Produce overview of transcription steps (initiation, elongation, termination)

Central Dogma of Biology Overview

  • DNA is the blueprint containing necessary information
  • DNA provides instructions via RNA to synthesize proteins
  • RNA acts as the messenger, moving from nucleus to cytosol
  • Proteins perform various functions as directed by DNA
    • RNA --> mRNA --> translated to proteins

Differences Between Prokaryotic and Eukaryotic Transcription

General Differences

  • Eukaryotes: Transcription occurs inside the nucleus
  • Prokaryotes: Transcription occurs in the cytosol

Prokaryotes

  • Genetic material (DNA) present in cytosol
  • RNA produced in prokaryotes is directly functional (mostly exons)
    • No junk DNA

Eukaryotes

  • Genetic material (DNA) within nucleus
  • Initial RNA (pre-mRNA) needs processing: exons and introns
    • Splicing: Removes introns, joining exons
    • 5' capping and 3' polyadenylation (poly-A tail)
    • Further modifications like RNA editing (less common)

Enzymes and Factors Involved in Transcription

  • RNA polymerase (specifically RNA polymerase II for prokaryotes)
  • Transcription factors (e.g., TF1, TF2, TF3)
  • Template needed for transcription (which DNA strand to use)
    • DNA is double-stranded
    • RNA is single-strand and uses uracil (U) instead of thymine (T)

Template vs. Coding Strand

  • RNA synthesis direction: 5' to 3'
  • Template strand: Complimentary to the RNA strand
  • Coding strand: Same sequence as RNA strand (except T replaced by U in RNA)

Example:

Coding strand: 5'-ATTGGCCTA-3' Template strand: 3'-TAACCGGAT-5' RNA: 5'-AUUGGCCUA-3'

Overview of DNA Transcription Process

Initiation

  1. Binding of RNA Polymerase
    • Binds to consensus sequence on DNA
  2. Role of Sigma Factor
    • Stabilizes RNA polymerase binding
  3. Scanning for Promoter Sequence
    • Movement to promoter site
  4. Formation of Closed Complex
    • Promoter site melting and bubble formation
    • Start of RNA synthesis on the template strand

Elongation

  • Continuous addition of ribonucleotides
  • RNA chain grows, synthesized from 5' to 3'

Termination

  1. Rho-dependent Termination
    • Rho protein (hexameric) attaches to RNA
    • Disassociates RNA from the DNA
  2. Rho-independent (Intrinsic) Termination
    • Formation of GC-rich stem-loops (hairpin structures)
    • Weak A-U bond interactions cause RNA release

Summary

  • Covered initiation, elongation, and termination
  • Next videos to delve deeper into each phase
    • Initiation
    • Elongation
    • Termination

Full transcript