3'-5'-DNA exonuclease activity

Definition

Target type: molecularfunction

Catalysis of the sequential cleavage of mononucleotides from a free 3' terminus of a DNA molecule. [GOC:mah]

3'-5'-DNA exonuclease activity refers to the enzymatic process of removing nucleotides from the 3' end of a DNA strand. This activity is crucial for various cellular processes, including DNA repair, replication, and recombination. The enzyme responsible for this activity is known as a 3'-5'-DNA exonuclease.

**Mechanism of Action:**

3'-5'-DNA exonuclease activity involves a series of steps:

1. **Binding:** The exonuclease enzyme binds to the 3' end of the DNA strand.
2. **Hydrolysis:** The enzyme catalyzes the hydrolysis of the phosphodiester bond between the 3' hydroxyl group of the penultimate nucleotide and the 5' phosphate group of the terminal nucleotide.
3. **Nucleotide Release:** The cleaved nucleotide is released from the DNA strand.
4. **Translocation:** The exonuclease enzyme then translocates to the next nucleotide, repeating the process until the desired number of nucleotides have been removed.

**Biological Significance:**

3'-5'-DNA exonuclease activity plays a critical role in maintaining the integrity of the genome. It is essential for:

* **DNA Repair:** Removing damaged or mismatched nucleotides during DNA repair pathways.
* **DNA Replication:** Processing Okazaki fragments during lagging strand synthesis.
* **Recombination:** Excising damaged DNA segments during homologous recombination.
* **Regulation of Gene Expression:** Removing specific nucleotides from DNA sequences to regulate gene expression.

**Examples of 3'-5'-DNA Exonucleases:**

* **DNA Polymerase I:** Possesses 3'-5'-exonuclease activity, which is used for proofreading during DNA replication.
* **Exonuclease I:** A dedicated 3'-5'-exonuclease involved in DNA repair and recombination.
* **RecBCD:** A complex with 3'-5'-exonuclease activity that plays a role in homologous recombination.

**Clinical Relevance:**

Defects in 3'-5'-DNA exonuclease activity can lead to various genetic disorders, including:

* **Bloom Syndrome:** A rare genetic disease characterized by an increased risk of cancer.
* **Xeroderma Pigmentosum:** A disorder characterized by extreme sensitivity to sunlight and an increased risk of skin cancer.
* **Ataxia Telangiectasia:** A neurodegenerative disorder with an increased risk of cancer.

**Conclusion:**

3'-5'-DNA exonuclease activity is a fundamental enzymatic process that plays a vital role in maintaining genome stability and regulating gene expression. Its importance in various cellular processes highlights its significance for human health.'
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Proteins (2)

Compounds (25)