Exonucleasemediated

Exonuclease-mediated refers to cellular and biochemical processes driven by exonuclease enzymes, which remove nucleotides from the ends of nucleic acid chains. Exonucleases differ from endonucleases in that they trim nucleotides one by one from a terminus rather than cutting within the strand. They can act in a 5' to 3' direction or a 3' to 5' direction, and their substrates include DNA or RNA, in single- or double-stranded form, depending on the enzyme.

In the 5' to 3' direction, exonucleases remove nucleotides starting at the 5' end, generating new 3' ends. In the 3' to 5' direction, exonucleases digest from the 3' end toward the 5' end, producing progressively shorter strands. Some exonucleases preferentially degrade single-stranded nucleic acids, while others act on double-stranded substrates or on specialized structures. Exonucleases often require metal ions such as magnesium or manganese to catalyze phosphodiester bond hydrolysis.

Biologically, exonuclease-mediated activities are central to DNA replication fidelity, DNA repair, and recombination. 3' to 5' exonuclease activity in DNA polymerases provides proofreading to correct misincorporated bases. Exonucleases participate in mismatch repair and in resection steps that generate 3' overhangs for homologous recombination. In RNA metabolism, exoribonucleases regulate RNA stability and quality control, contributing to decay pathways and processing of ribosomal and messenger RNA.

Commonly used examples in research and biotechnology include Exonuclease I and Exonuclease III for DNA digestion, and lambda exonuclease for strand-specific processing of double-stranded DNA. Exonuclease-mediated strategies are employed to generate defined DNA ends, remove damaged termini, or trim substrates in sequencing and cloning workflows.