full issue - Association of Biotechnology and Pharmacy
full issue - Association of Biotechnology and Pharmacy
full issue - Association of Biotechnology and Pharmacy
You also want an ePaper? Increase the reach of your titles
YUMPU automatically turns print PDFs into web optimized ePapers that Google loves.
Current Trends in <strong>Biotechnology</strong> <strong>and</strong> <strong>Pharmacy</strong><br />
Vol. 5 (3) 1206-1232 July 2011, ISSN 0973-8916 (Print), 2230-7303 (Online)<br />
1224<br />
Fig. 5. Signaling pathways in NHEJ repair mechanism prokaryotes with Ku protein <strong>and</strong> LigD. Possible mechanisms<br />
that could be a drug target in the Ku protein. A. Pathway: Ku homodimer binds DBS, then LigD binds to a phosphate 5´<br />
<strong>and</strong> promotes end-synapsis, which with the nuclease process break termini <strong>and</strong> finally nick ligation. B. Target: Ku<br />
homodimer binds DBS, then Ku target bind to Ku <strong>and</strong> disrupts repair.<br />
by homologous recombination cannot function<br />
during the germination <strong>of</strong> spores (78).<br />
A different repair pathway to HR for DSB<br />
induced in spore DNA, nonhomologous-end<br />
joining (NHEJ) has recently been identified in<br />
B. subtilis, a Ku homolog (encoded by the ykoV<br />
gene). The bacterial Ku recruits a DNA ligase<br />
(encoded by ykoU) to DNA ends <strong>and</strong> in this<br />
manner stimulates DNA ligation (78). Bacillus<br />
subtilis has a heterodimer Ku 70/80 YkoU <strong>and</strong> a<br />
protein with few homologies to ADN ligase IV<br />
YkoV.<br />
5.2.2.2. Mycobacterium sp. Case: Nonhomologous<br />
end-joining (NHEJ) pathway with protein<br />
Ku <strong>and</strong> DNA ligase (LigD) is used by<br />
Mycobacteria to repair DNA double-str<strong>and</strong><br />
breaks (DSBs). The mechanisms <strong>of</strong><br />
mycobacterial NHEJ depend on the structures<br />
<strong>of</strong> the DSBs <strong>and</strong> end-processing <strong>and</strong> end-sealing<br />
components (77). The Ku like genes are <strong>of</strong>ten<br />
genetically linked in operons with another gene<br />
that encodes an ATP-dependent DNA ligase. It<br />
has been also established in Mycobacterium<br />
tuberculosis that Ku (Mt-Ku) <strong>and</strong> ligase (Mt-lig)<br />
proteins, together reconstitute a mechanism with<br />
capacity for ligation (79). Ku in Mycobacterium<br />
tuberculosis is a homodimer, which binds only<br />
to linear DNA ends.<br />
5.2.2.3. E. coli: Other bacteria, where Ku-like<br />
<strong>and</strong> Ligase-D-like proteins have not been found,<br />
DNA repair mechanisms in prokaryotes