Exoribonuclease

Exoribonuclease

Diagram of 3' RNA degradation by exoribonuclease

Exoribonucleases are enzymes that degrade RNA molecules from their ends. They play a crucial role in the RNA degradation process, which is essential for the regulation of gene expression and the maintenance of cellular RNA levels. Exoribonucleases are involved in the processing and turnover of various types of RNA, including messenger RNA (mRNA), ribosomal RNA (rRNA), and transfer RNA (tRNA).

Function

Exoribonucleases function by cleaving nucleotides one at a time from the end of an RNA molecule. They can act in either the 5' to 3' direction or the 3' to 5' direction, depending on the specific enzyme and its role in the cell. This process is critical for the removal of defective or unnecessary RNA molecules, thereby preventing the accumulation of potentially harmful RNA species within the cell.

Types of Exoribonucleases

There are several types of exoribonucleases, each with specific functions and substrate preferences:

• 3' to 5' Exoribonucleases: These enzymes degrade RNA from the 3' end towards the 5' end. They are often involved in the final steps of RNA decay and processing.
• 5' to 3' Exoribonucleases: These enzymes degrade RNA from the 5' end towards the 3' end. They are typically involved in the initial stages of RNA decay.

Biological Importance

Exoribonucleases are essential for the regulation of gene expression. By controlling the degradation of mRNA, they influence the levels of proteins synthesized within the cell. This regulation is vital for cellular responses to environmental changes and developmental signals.

Additionally, exoribonucleases are involved in the quality control of RNA molecules. They help eliminate defective RNA transcripts that could otherwise lead to the production of malfunctioning proteins.

Mechanism of Action

Exoribonucleases recognize and bind to the ends of RNA molecules. They then catalyze the hydrolysis of phosphodiester bonds, releasing nucleotides one at a time. This process continues until the entire RNA molecule is degraded or until the enzyme encounters a structural barrier, such as a stable secondary structure or a bound protein.

Related Pages

• RNA degradation
• Gene expression
• Messenger RNA
• Ribosomal RNA
• Transfer RNA