rRNA Structure, Processing, Regulation, and Function

Structure

• rRNA (ribosomal RNA) is a type of non-coding RNA that makes up a large part of the ribosome
• Composed of two main components: 18S and 28S rRNA in eukaryotes, and 16S and 23S rRNA in prokaryotes
• 18S/16S rRNA forms the small subunit of the ribosome, while 28S/23S rRNA forms the large subunit
• rRNA is highly structured, with many stem-loop and pseudoknot structures

Processing

• rRNA is synthesized as a precursor molecule, which is then processed to form the mature rRNA
• Processing involves:
  • Cleavage of the precursor molecule to form the individual rRNA components
  • Modification of the rRNA, such as methylation and pseudouridylation
  • Assembly of the rRNA into the ribosome
• Processing occurs in the nucleolus, a region within the nucleus

Regulation

• rRNA synthesis is regulated by a variety of mechanisms, including:
  • Transcriptional regulation: controlling the rate of rRNA synthesis
  • Post-transcriptional regulation: controlling the processing and stability of rRNA
  • Epigenetic regulation: controlling the accessibility of rRNA genes to transcription factors
• Regulation is important for maintaining cellular homeostasis and responding to changes in the environment

Function

• rRNA plays a central role in protein synthesis, providing the platform for mRNA translation
• rRNA recognizes and binds to mRNA, positioning it for translation
• rRNA also catalyzes peptide bond formation during translation
• rRNA is essential for cell growth and survival

Synthesis

• rRNA synthesis occurs in the nucleolus, where the genes for rRNA are transcribed by RNA polymerase I
• rRNA synthesis is a rapid and highly efficient process, with cells producing thousands of rRNA molecules per minute
• Synthesis is regulated by a variety of factors, including growth factors, nutrient availability, and stress signals
• rRNA synthesis is coordinated with the synthesis of ribosomal proteins to ensure the proper assembly of the ribosome