The Mechanism Of OGG1 In Regulating NF-κB RelA/P65 Ser276 Phosphorylation

The genomes of living organisms are continuously exposed to reactive oxygen species(ROS)derived from the normal metabolism,as well as from pathophysiological processes caused by exposure to physical,chemical,or infectious agents.ROS inflict oxidative damage on various macromolecules,including proteins,lipids,and nucleic acids.Repair of DNA lesions is crucial for maintaining genomic integrity,whereas other oxidatively damaged macromolecules undergo degradation.One of the most abundant oxidized DNA lesions is 8-oxo-7,8-dihydroguanine(8-oxoG),as guanine has the lowest oxidation potential among the four bases in DNA.The repair of 8-oxoG is important because it can mispair with adenine,which results in a G:C to T:A transversion during replication,leading to mutations.In mammalian cells the enzyme catalyzing the excision of the 8-oxoG base from the DNA duplex is 8-oxoguanine DNA glycosylase-1.8-oxoG is primarily repaired via the 8-oxoguanine DNA glycosylase1(OGG1)-initiated base excision repair pathway.Vertebrate genome evolutionarily has a high GC content in the promoter regions of RNA polymerase(Pol)II–transcribed genes,despite guanine’s vulnerability to be oxidizedto the mutagenic 8-oxoG and subjected to DNA repair.For instance,a genomic-wide survey revealed that 72% of promoters belong to a class with high CpG content.Also,the consensus binding sites for many transcription factors(e.g.,specificity protein 1 [Sp1] and NF-?B)are guanine-rich.We thus speculate that the high GC content in promoter regions is an advantage for transcriptional regulation due to nonproductive binding of OGG1 to 8-oxoG under conditions of oxidative stress.We also showed that TNF-α–induced phosphorylation of NF-?B/RelA at Ser276(p–NF-?B/RelA)and its nuclear translocation are tightly associated with ROS signaling,and that inhibition of TNF-α–induced ROS blocks the activities of kinases and decreases NF-?B/p-RelA levels.Importantly,we showed that p–NF-?B/RelA stable enhanceosome formation with p300 and p-RNA Pol II and binding to the gene promoter are ROS dependent.Our data show that exposure of cells to TNF-α altered cellular redox,increased the 8-oxoG level in DNA,recruited OGG1 to promoter sequences,and transiently inhibited base excision repair of 8-oxoG.Promoter-associated OGG1 then enhanced NF-?B/RelA binding to cis-elements and facilitated recruitment of specificity protein 1,transcription initiation factor II-D,and p-RNA polymerase II,resulting in the rapid expression of chemokines/cytokines and inflammatory cell accumulation in mouse airways.Small interfering RNA depletion of OGG1 or prevention of guanine oxidation significantly decreased TNF-α–induced inflammatory responses.Our preliminary data also show that the deficent of ogg1 will reduce the phosphorylation level of NF-?B/RelA Ser276.We hypothesized that OGG1 may be involved in the post-translational modification of NF-?B.This arrangement of the presence of oxidative-reduction,inactivationrepair time between proteins and DNA should be a mechanism for the clever use of ROS signaling in gene transcription regulation.In this study,we conducted the following experiments: TNF-α induced ROS-sensitive NF-κB-dependent expression of inflammatory genes,OGG1 interacts with MSK1 to participate in the regulation of the process and so on.We found that TNF-α stimulation not only activated NF-κB p50-RelA / p65 dimer into the nucleus,but also induced NF-κB post-translational modification,that NF-?B/RelA Ser276 phosphorylation.However,the entry of NF-κB RelA / p65 does not depend on the phosphorylation of NF-?B/RelA S276,suggesting that our post-translational modification of NF-κB is more important and may contribute to the binding of NF-κB to DNA,Facilitating the assembly of transcription initiation complexes and extension of transcription.the primary ablation repair function temporarily inactivated OGG1 did not participate in the regulation of TNF-α stimulation induced NF-κB p50-RelA / p65 dimer into the nucleus process.OGG1,which is predominantly located in the nucleus,rapidly recognizes and binds to 8-oxoG in the promoter region of the oxygen-sensitive gene,recruiting NF-κB to recognize its conserved sequence.under oxidative stress,We also found that OGG1 indirectly interacts with MSK1 kinase to regulate the post-translational modification of NF-κB,the phosphorylation of RelA / p65 Ser276.The above results reveal the new molecular function of OGG1 in DNA transcription events,but the specific molecular mechanisms of interaction between the two proteins,as well as the specific signaling pathways involved in this process,are unclear and require more experiments and a large number ofdata to be described.it could be proposed that modulation of OGG1 activity might be a therapeutic target in the resolution of inflammatory processes that impair organ integrity and promote aging processes,as increased OGG1 activity would be expected to decrease the expression of proinflammatory genes and recruitment of inflammatory cells.