DNA Ligases: It play an essential role in maintaining genomic integrity by joining breaks in the phosphodiester backbone of DNA that occur during replication and recombination, and as a consequence of DNA damage and its repair. Three human genes, LIG1, LIG3 and LIG4 encode ATP-dependent DNA ligases. These enzymes have related catalytic regions that catalyze the same three-step ligation reaction but different flanking domains that mediate protein:protein interactions with different partners.

Functions of DNA Ligases

• It play an essential role in DNA replication, repair, and recombination and are classified as ATP-dependent or NAD-dependent based on their adenylation cofactor requirement.
• It helps to maintain genomic integrity is immense. It does so by joining the breaks in the DNA’s phosphodiester backbone occurring while recombination and replication take place in addition to the result of DNA damage and its repairing.
• The primary role is to ligate two strands of DNA, which could be single or double strands despite the fact that ligases are differently used for various purposes in vitro and vivo processes.

Types of DNA Ligase

• DNA Ligase I – It ligates the nascent DNA on the lagging strand particularly the gaps between the Okazaki fragments.
• DNA Ligase II – These are not deemed to be true ligases as it does not possess its own gene. The eukaryotic DNA ligase II is generated from gene encoding DNA ligase III. Primarily, it participates in the DNA repair pathway.
• DNA Ligase III – Participates in the DNA repair, particularly the nucleotide excision repair. This ligase is the one found in the mitochondrial DNA also.
• DNA Ligase IV – It joins double-stranded DNA and does take part in double-strand break repair pathway, specially, the non-homologous end-joining.

DNA Ligases in Biotechnology

It is used to join two fragments of DNA to seal the gaps between them. Thus, they are known as molecular glues. Only the matching DNA fragments with complementary ends can be joined with DNA ligase. Ligation is a natural process during replication process where Okazaki fragments are joined together. Ligation is carried out for the purpose of cloning in the laboratory.

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By Team Learning Mantras