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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).
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.
DNA ligase 1 also DNA ligase I, is an enzyme that in humans is encoded by the LIG1 gene. DNA ligase 1 is the only known eukaryotic DNA ligase involved in both DNA replication and repair , making it the most studied of the ligases .
The smallest known eukaryotic ligase is Chlorella virus DNA ligase (ChVLig). It contains only 298 amino acids. When ChVLig is the only source of ligase in the cell, it can continue to support mitotic development, and nonhomologous end joining in budding yeasts. [34] DNA Ligase I (Lig1) is accountable for Okazaki Fragments ligation.
Pathway preference may differ between organisms, as well. While human cells utilize both short- and long-patch BER, the yeast Saccharomyces cerevisiae was long thought to lack a short-patch pathway because it does not have homologs of several mammalian short-patch proteins, including pol β, DNA ligase III, XRCC1, and the kinase domain of PNKP.
[26] [27] While the precise role of XLF is unknown, it interacts with the XRCC4/DNA ligase IV complex and likely participates in the ligation step. [28] Recent evidence suggests that XLF promotes re-adenylation of DNA ligase IV after ligation, recharging the ligase and allowing it to catalyze a second ligation. [29]
In humans, mutational defects in the ERCC5(XPG) gene can cause either the cancer-prone condition xeroderma pigmentosum (XP) alone, or in combination with the severe neurodevelopmental disorder Cockayne syndrome (CS) or the infantile lethal cerebro-oculo-facio-skeletal syndrome. [24]
DNA ligase 3 also DNA ligase III, is an enzyme that, in humans, is encoded by the LIG3 gene. [ 5 ] [ 6 ] LIG3 encodes ATP -dependent DNA ligases that seal interruptions in the phosphodiester backbone of duplex DNA .