Ligase eukaryotic

The third type of E3 ligases is represented by the polycomb protein 2 (Pc2), which was reported to enhance sumoylation of the substrate CtBP. N- and C-terminal domains in Pc2 that have been implicated in CtBP sumoylation do not resemble known E3 ligases. Like RanBP2, Pc2 expression is restricted to higher eukaryotes. 

Conserved catalytic (adenylation) domain in NAD-dependent (bacterial) and ATP-dependent (archaeal-eukaryotic) DNA ligases (Aravind and Koonin, 1999) Conserved nucleotide joining-cleaving domain in type I and II topoisomerases, DnaG-type primases, OLD nucleases, and RecR (Toprim domain) (Aravind et al, 1998b)... 

DNA ligase catalyzes the formation of a phosphodi-ester bond between a 3 hydroxyl at the end of one DNA strand and a 5 phosphate at the end of another strand. The phosphate must be activated by adenylyla-tion. DNA ligases isolated from viruses and eukaryotes use ATP for this purpose. DNA ligases from bacteria are unusual in that they generally use NAD+—a cofactor that normally functions in hydride transfer reactions... 

Know the roles of DNA polymerase I, II, III, and eukaryotic DNA polymerases, the roles of primers, helicases, single-stranded binding proteins (SSB), topoisomerases (gyrase), ligases, primase, and RNA polymerases, and the differences between the leading and lagging strands of DNA. 

Fig. 16-13 The reaction catalyzed by DNA ligase in E. coli. (NMN = nicotinamide mononucleotide.) Eukaryotic ligases use ATP instead of NAD+ as the coreactant.

DNA strand. At the expense of one molecule of ATP, two DNA strands are joined via a phosphodi-ester bond. Although eukaryotic and T4 phage DNA ligase use ATP as the adenyl group donor in this reaction, E. coli DNA ligase utilizes NAD+ (Fig. V-16). 

In NHEJ in eukaryotes, the Ku heterodimer binds to both ends of the double-strand break (32) and recruits DNA-PKcs and the ligase IV-XRCC4 heterodimer. These then ligate both ends of the double-strand break regardless of whether they actually come from the same chromosome (33). In NHEJ, Artemis is the end-processing nuclease (34) (Fig. 8). 

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