Cooperation of PprI and DrRRA in response to extreme ionizing radiation in Deinococcus radiodurans

Effects of anger and trigger identity on triggered displaced aggression among college students: based on the "kicking the barking dog effect"

BACKGROUND

Drawing on the "kicking the barking dog effect", this study investigated the individual and group-level mechanisms underlying triggered displaced aggression (TDA).

METHODS

Three experiments were conducted to investigate the effects of anger and hostile attribution on TDA, examining these factors at both the individual and group levels. The preliminary experiment investigated how emotions affect subsequent cognition at an individual level with the aim of understanding the underlying generative process of TDA. Experiment 1 explored the relationship between anger, hostile attribution, and subsequent aggressive behaviors at an individual level, while also discussing the underlying generative process of TDA. Experiment 2 investigated the relationship between anger, hostile attribution, and subsequent aggressive behaviors from a group-level perspective, while also delving into the impact of trigger identity on the underlying generative process of TDA.

RESULTS

When individuals were exposed to both a provocation and a subsequent triggering situation, they demonstrated stronger hostile attribution and displayed more aggressive behavior directed toward the trigger. This study found that hostile attribution played a complete mediating role in the influence of anger on TDA, while the triggering situation itself had a moderating role. In the presence of triggering situations, individuals exhibited stronger hostile attribution as their level of anger increased. In the absence of a triggering situation, changes in anger level did not have a significant effect. In the presence of a triggering situation, the identity of the trigger played a moderating role in the process of "anger → hostile attribution → TDA". When the trigger belonged to an in-group, individuals exhibited stronger hostile attribution toward the out-group and subsequently displayed greater TDA.

CONCLUSION

These findings expand the applicability of the "kicking the barking dog effect" and offer suggestions for controlling the escalation of intergroup conflicts.

PprI: The Key Protein in Response to DNA Damage in Deinococcus

Deoxyribonucleic acid (DNA) damage response (DDR) pathways are essential for maintaining the integrity of the genome when destabilized by various damaging events, such as ionizing radiation, ultraviolet light, chemical or oxidative stress, and DNA replication errors. The PprI–DdrO system is a newly identified pathway responsible for the DNA damage response in Deinococcus, in which PprI (also called IrrE) acts as a crucial component mediating the extreme resistance of these bacteria. This review describes studies about PprI sequence conservation, regulatory function, structural characteristics, biochemical activity, and hypothetical activation mechanisms as well as potential applications.

Structural and Functional Characterization of a Unique AP Endonuclease From Deinococcus radiodurans

Various endogenous and exogenous agents cause DNA damage, including apurinic/apyrimidinic (AP) sites. Due to their cytotoxic effects, AP sites are usually cleaved by AP endonuclease through the base excision repair (BER) pathway. Deinococcus radiodurans, an extraordinary radiation-resistant bacterium, is known as an ideal model organism for elucidating DNA repair processes. Here, we have investigated a unique AP endonuclease (DrXth) from D. radiodurans and found that it possesses AP endonuclease, 3'-phosphodiesterase, 3'-phosphatase, and 3'-5' exonuclease but has no nucleotide incision repair (NIR) activity. We also found that Mg²⁺ and Mn²⁺ were the preferred divalent metals for endonuclease and exonuclease activities, respectively. In addition, DrXth were crystallized and the crystals diffracted to 1.5 Å. Structural and biochemical analyses demonstrated that residue Gly198 is the key residue involved in the substrate DNA binding and cleavage. Deletion of the drxth gene in D. radiodurans caused elevated sensitivity to DNA damage agents and increased spontaneous mutation frequency. Overall, our results indicate that DrXth is an important AP endonuclease involved in BER pathway and functions in conjunction with other DNA repair enzymes to maintain the genome stability.

Improved tolerance of Escherichia coli to oxidative stress by expressing putative response regulator homologs from Antarctic bacteria

Response regulator (RR) is known a protein that mediates cell's response to environmental changes. The effect of RR from extremophiles was still under investigation. In this study, response regulator homologs were mined from NGS data of Antarctic bacteria and overexpressed in Escherichia coli. Sixteen amino acid sequences were annotated corresponding to response regulators related to the two-component regulatory systems; of these, 3 amino acid sequences (DRH632, DRH1601 and DRH577) with high homology were selected. These genes were cloned in pRadGro and expressed in E. coli. The transformant strains were subjected to various abiotic stresses including oxidative, osmotic, thermal stress, and acidic stress. There was found that the robustness of E. coli to abiotic stress was increased in the presence of these response regulator homologs. Especially, recombinant E. coli overexpressing drh632 had the highest survival rate in oxidative, hypothermic, osmotic, and acidic conditions. Recombinant E. coli overexpressing drh1601 showed the highest tolerance level to osmotic stress. These results will be applicable for development of recombinant strains with high tolerance to abiotic stress.

Antioxidative system of Deinococcus radiodurans

Deinococcus radiodurans is famous for its extreme resistance to various stresses such as ionizing radiation (IR), desiccation and oxidative stress. The underlying mechanism of exceptional resistance of this robust bacterium still remained unclear. However, the antioxidative system of D. radiodurans has been considered to be the determinant factor for its unparalleled resistance and protects the proteome during stress, then the DNA repair system and metabolic system exert their functions to restore the cell to normal physiological state. The antioxidative system not only equipped with the common reactive oxygen species (ROS) scavenging enzymes (e.g., catalase and superoxide dismutase) but also armed with a variety of non-enzyme antioxidants (e.g., carotenoids and manganese species). And the small manganese complexes play an important role in the antioxidative system of D. radiodurans. Recent studies have characterized several regulators (e.g., PprI and PprM) in D. radiodurans, which play critical roles in the protection of the bacteria from various stresses. In this review, we offer a panorama of the progress regarding the characteristics of the antioxidative system in D. radiodurans and its application in the future.

Proteomic insights into the functional basis for the response regulator DrRRA of Deinococcus radiodurans

Purpose To investigate the function basis of the recently discovered response regulator, drRRA (DNA damage response regulator A) in Deinococcus radiodurans, we compared the proteomic profile of the radiation-sensitive drRRA mutant with that of wild-type strain under both non-stress and gamma radiation treatment. Materials and methods Total proteins of D. radiodurans cells were subjected to two-dimension electrophoresis. Protein spots in 2-Dimension gels were silver stained and scanned. Spots that changed significantly in expression levels were selected for mass spectrometry analysis. Seven genes encoding representative proteins were knocked out for stress resistance analysis. Results A total of 52 proteins displayed significant expression level changes at least 1.5-fold in the mutant relative to wild-type strain under non-stress conditions, with 31 repressed and 21 induced proteins, which might affect the cell response of D. radiodurans to gamma radiation. The proteins were distributed into functional groups including stress response, metabolism, and function unknown. Disruptions of several altered proteins including DRA0259 (Catalase E) and DR1538 (Osmotically inducible protein C), reduced the antioxidant activity of D. radiodurans. Conclusion Combined with our previous result of transcriptional profile, we further confirmed that inactivation of DrRRA affects the expression of various stress response systems.

DNA repair in hyperthermophilic and hyperradioresistant microorganisms

The genome of a living cell is continuously under attack by exogenous and endogenous genotoxins. Especially, life at high temperature inflicts additional stress on genomic DNA, and very high rates of potentially mutagenic DNA lesions, including deamination, depurination, and oxidation, are expected. However, the spontaneous mutation rates in hyperthermophiles are similar to that in Escherichia coli, and it is interesting to determine how the hyperthermophiles preserve their genomes under such grueling environmental conditions. In addition, organisms with extremely radioresistant phenotypes are targets for investigating special DNA repair mechanisms in extreme environments. Multiple DNA repair mechanisms have evolved in all organisms to ensure genomic stability, by preventing impediments that result in genome destabilizing lesions.

Expression and mutational analysis of DinB-like protein DR0053 in Deinococcus radiodurans

In order to understand the mechanism governing radiation resistance in Deinococcus radiodurans, current efforts are aimed at identifying potential candidates from a large repertoire of unique Deinococcal genes and protein families. DR0053 belongs to the DinB/YfiT protein family, which is an over-represented protein family in D. radiodurans. We observed that dr0053 transcript levels were highly induced in response to gamma radiation (γ-radiation) and mitomycin C (MMC) exposure depending on PprI, RecA and the DrtR/S two-component signal transduction system. Protein profiles demonstrated that DR0053 is a highly induced protein in cultures exposed to 10 kGy γ-radiation. We were able to determine the transcriptional start site of dr0053, which was induced upon irradiation, and to assign the 133-bp promoter region of dr0053 as essential for radiation responsiveness through primer extension and promoter deletion analyses. A dr0053 mutant strain displayed sensitivity to γ-radiation and MMC exposure, but not hydrogen peroxide, suggesting that DR0053 helps cells recover from DNA damage. Bioinformatic analyses revealed that DR0053 is similar to the Bacillus subtilis protein YjoA, which is a substrate of bacterial protein-tyrosine kinases. Taken together, the DNA damage-inducible (din) gene dr0053 may be regulated at the transcriptional and post-translational levels.

A PerR-like protein involved in response to oxidative stress in the extreme bacterium Deinococcus radiodurans

Response and defense systems against reactive oxygen species (ROS) contribute to the remarkable resistance of Deinococcus radiodurans to oxidative stress induced by oxidants or radiation. However, mechanisms involved in ROS response and defense systems of D. radiodurans are not well understood. Fur family proteins are important in ROS response. Only a single Fur homolog is predicted by sequence similarity in the current D. radiodurans genome database. Our bioinformatics analysis demonstrated an additional guanine nucleotide in the genome of D. radiodurans that is not in the database, leading to the discovery of another Fur homolog DrPerR. Gene disruption mutant of DrPerR showed enhanced resistance to hydrogen peroxide (H2O2) and increased catalase activity in cell extracts. Real-time PCR results indicated that DrPerR functions as a repressor of the catalase gene katE. Meanwhile, derepression of dps (DNA-binding proteins from starved cells) gene under H2O2 stress by DrPerR point to its regulatory role in metal ions hemostasis. Thus, DrPerR might function as a Fur homolog protein which is involved in ROS response and defense. These results help clarify the complicated regulatory network that responds to ROS stress in D. radiodurans.