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DNA ligase is a type of enzyme that facilitates the joining of DNA strands together by catalyzing the formation of a phosphodiester bond.It plays a role in repairing single-strand breaks in duplex DNA in living organisms, but some forms (such as DNA ligase IV) may specifically repair double-strand breaks (i.e. a break in both complementary strands of DNA).
Eukaryotic DNA ligase 1 catalyzes a reaction that is chemically universal to all ligases. DNA ligase 1 utilizes adenosine triphosphate (ATP) to catalyze the energetically favorable ligation events in both DNA replication and repair. During the synthesis phase (S-phase) of the eukaryotic cell cycle, DNA replication occurs.
The cell cycle is a series of complex, ordered, sequential events that control how a single cell divides into two cells, and involves several different phases. The phases include the G1 and G2 phases, DNA replication or S phase, and the actual process of cell division, mitosis or M phase. [1]
S phase (Synthesis phase) is the phase of the cell cycle in which DNA is replicated, occurring between G 1 phase and G 2 phase. [1] Since accurate duplication of the genome is critical to successful cell division, the processes that occur during S-phase are tightly regulated and widely conserved.
The mechanism of the ligation reaction was first elucidated in the laboratory of I. Robert Lehman. [4] [5] Two fragments of DNA may be joined by DNA ligase which catalyzes the formation of a phosphodiester bond between the 3'-hydroxyl group (-OH) at one end of a strand of DNA and the 5'-phosphate group (-PO4) of another.
In biochemistry, a ligase is an enzyme that can catalyze the joining of two molecules by forming a new chemical bond. This is typically via hydrolysis of a small pendant chemical group on one of the molecules, typically resulting in the formation of new C-O, C-S, or C-N bonds.
Instead, the pre-RC that is formed during the G 1 of the cell cycle is only activated to unwind the DNA and initiate replication after the cells pass from the G 1 to the S phase of the cell cycle. [2] Once the initiation complex is formed and the cells pass into the S phase, the complex then becomes a replisome.
In molecular biology and biochemistry, processivity is an enzyme's ability to catalyze "consecutive reactions without releasing its substrate". [1]For example, processivity is the average number of nucleotides added by a polymerase enzyme, such as DNA polymerase, per association event with the template strand.