BRD4 inhibitors broadly promote erastin-induced ferroptosis in different cell lines by targeting ROS and FSP1.

Ferroptosis, an iron-dependent form of programmed cell death, is a promising strategy for cancer treatment. Bromodomain-containing protein 4 (BRD4) is an epigenetic reader and a promising target for cancer therapeutics. However, the role of BRD4 in ferroptosis is controversial and the value of the interaction between BRD4 inhibitors and ferroptosis inducers remains to be explored. Here, we found that BRD4 inhibition greatly enhanced erastin-induced ferroptosis in different types of cells, including HEK293T, HeLa, HepG2, RKO, and PC3 cell lines. Knocking down BRD4 in HEK293T and HeLa cells also promoted erastin-induced cell death. BRD4 inhibition by JQ-1 and I-BET-762 or BRD4 knockdown resulted in substantial accumulation of reactive oxygen species (ROS) in both HEK293T and HeLa cells. The effect of BRD4 inhibition on ferroptosis-associated genes varied in different cells. After using BRD4 inhibitors, the expression of FTH1, Nrf2, and GPX4 increased in HEK293T cells, while the levels of VDAC2, VDAC3, and FSP1 decreased. In HeLa cells, the expression of FTH1, VDAC2, VDAC3, Nrf2, GPX4, and FSP1 was reduced upon treatment with JQ-1 and I-BET-762. Consistently, the level of FSP1 was greatly reduced in HEK293T and HeLa cells with stable BRD4 knockdown compared to control cells. Furthermore, ChIP-sequencing data showed that BRD4 bound to the promoter of FSP1, but the BRD4 binding was greatly reduced upon JQ-1 treatment. Our results suggest that ROS accumulation and FSP1 downregulation are common mechanisms underlying increased ferroptosis with BRD4 inhibitors. Thus, BRD4 inhibitors might be more effective in combination with ferroptosis inducers, especially in FSP1-dependent cancer cells.

Triad3A involved in the regulation of endotoxin tolerance and mycobactericidal activity through the NFκB-nitric oxide pathway.

INTRODUCTION: Sepsis is characterized by an endotoxin tolerance phenotype that occurs in the stage of infection. Persistent bacterial infection can lead to immune cell exhaustion. Triad3A, an E3 ubiquitin ligase, negatively regulates its activation by TLR4. However, the effect of Triad3A on endotoxin tolerance and bactericidal ability in the state of endotoxin tolerance remains unclear. METHODS: Using single dose LPS and repeated LPS stimulated macrophage cell lines at indicated times, we investigated miR-191, Tirad3A, TRAF3, TLR4, p-P65, TNF-α, IL-1ß, and iNOS expression, the effect of miR-191 on Triad3A and TRAF3, gene loss-of-function analyses, the effect of Triad3A on TLR4, p-P65, cytokine, and mycobactericidal activity in endotoxin tolerant cells infected with Mycobacterium marinum. RESULTS: Here we found that Triad3A is involved in regulating endotoxin tolerance. Our result also displayed that miR-191 expression is downregulated in macrophages in the state of endotoxin tolerance. miR-191 can directly bind to Triad3A and TRAF3. Additionally, knockdown of Triad3A can reverse the effect of decreasing TNF-α and IL-1ß in endotoxin tolerant macrophages. Furthermore, we demonstrated that the TLR4-NF-κB-NO pathway was associated with Triad3A and responsible for the killing of intracellular mycobacteria in a tuberculosis sepsis model. CONCLUSIONS: These results provide new insight into the mechanisms of Triad3A induced tolerogenic phenotype in macrophages, which can help the better comprehension of the pathogenesis involved in septic shock with infection of Mycobacterium tuberculosis, and suggest that Triad3A may be a potential drug target for the treatment of severe septic tuberculosis.

Immune checkpoint modulating T cells and NK cells response to Mycobacterium tuberculosis infection.

Many subversive mechanisms promote the occurrence and development of chronic infectious diseases and cancer, among which the down-regulated expression of immune-activating receptors and the enhanced expression of immune-inhibitory receptors accelerate the occurrence and progression of the disease. Recently, the use of immune checkpoint inhibitors has shown remarkable efficacy in the treatment of tumors in multiple organs. However, the expression of immune checkpoint molecules on natural killer (NK) cells by Mycobacterium tuberculosis (Mtb) infection and its impact on NK cell effector functions have been poorly studied. In this review, we focus on what is currently known about the expression of various immune checkpoints in NK cells following Mtb infection and how it alters NK cell-mediated host cytotoxicity and cytokine secretion. Unraveling the function of NK cells after the infection of host cells by Mtb is crucial for a comprehensive understanding of the innate immune mechanism of NK cells involved in tuberculosis and the evaluation of the efficacy of immunotherapies using immune checkpoint inhibitors to treat tuberculosis. In view of some similarities in the immune characteristics of T cells and NK cells, we reviewed the molecular mechanism of the interaction between T cells and Mtb, which can help us to further understand and explore the specific interaction mechanism between NK cells and Mtb.

Upregulation of CD226 on subsets of T cells and NK cells is associated with upregulated adhesion molecules and cytotoxic factors in patients with tuberculosis.

Human T cells and natural killer (NK) cells are major effector cells of innate immunity exerting potential immune surveillance against tuberculosis infection. CD226 is an activating receptor playing vital roles in the functions of T cells and NK cells during HIV infection and tumorigenesis. However, CD226 is a less-studied activating receptor during Mycobacterium tuberculosis (Mtb) infection. In this study, we used peripheral blood from tuberculosis patients and healthy donors to evaluate CD226 immunoregulation functions from two independent cohorts using Flow cytometry. Here, we found that a subset of T cells and NK cells that constitutively express CD226 exhibit a distinct phenotype in TB patients. In fact, the proportions of CD226+ and CD226- cell subsets differ between healthy people and tuberculosis patients, and the expression of immune checkpoint molecules (TIGIT, NKG2A) and adhesion molecules (CD2, CD11a) in CD226+ and CD226- subsets of T cells and NK cells exhibits special regulatory roles. Furthermore, CD226+ subsets produced more IFN-γ and CD107a than CD226- subsets in tuberculosis patients. Our results imply that CD226 may be a potential predictor of disease progression and clinical efficacy in tuberculosis by mediating the cytotoxic capacity of T cells and NK cells.

The relationship between previous pulmonary tuberculosis and risk of lung cancer in the future.

Various investigations have expanded the views that tuberculosis is an important risk factor for lung cancer occurrence. Lung cancer originates from chronic inflammation and infection. It is becoming clearer that Mycobacterium tuberculosis (M.tb) in tuberculosis patients meticulously schemes multiple mechanisms to induce tumor formation and is indispensable to participate in the occurrence of lung cancer. In addition, some additional factors such as age, sex and smoking, accelerate the development of lung cancer after Mycobacterium tuberculosis infection. The clarification of these insights is fostering new diagnoses and therapeutic approaches to prevention of the patients developing from tuberculosis into lung cancer.

B and T lymphocyte attenuator as a C-reactive protein and IgA associated auxiliary diagnostic marker for pulmonary tuberculosis: a case-control study.

Background: Screening and identification of hematologic molecular indicators of pulmonary tuberculosis (PTB) is crucial for its diagnose and therapy. Therefore, our work aims to detect the diagnostic value of blood marker B and T lymphocyte attenuator (BTLA) in PTB, and provide a certain theoretical basis for the auxiliary diagnosis of PTB. Methods: Based on the inclusion criteria, 56 Patients with clinically confirmed pulmonary TB by clinical between January 2020 and December 2021 at our hospital were selected as the research objects of this study. Fifty-two matched healthy population at our hospital was used as the control group. Clinical characteristics were got from clinical laboratory. Real-time polymerase chain reaction (RT-PCR) was used to analyze changes in BTLA along with its ligand in peripheral blood. Changes in BTLA on the surface of different cells were analyzed by flow cytometry. The correlation test was used to determine the associations between BTLA and clinical indicators. Receiver operating characteristic (ROC) curve analysis was used to evaluate the auxiliary diagnostic value in PTB of BTLA expression from different sources. Results: Compared with the control, changes in peripheral blood BTLA in the PTB group were significantly increased (P=0.0187) rather than its ligand. Changes in BTLA on the surface of CD68 and antigen-presenting cell (APC) CD11c were significantly increased in the PTB group (P=0.0004, P<0.0001), while changes in BTLA on the surface of CD4+ T and CD8+ T cells were not significantly different (P=0.0792, P=0.8706). The expression of BTLA+CD11c+ was negatively correlated with the expression of immunoglobulin A (IgA) (r=-0.2934, P=0.0282) and positively related to C-reactive protein (r=0.3277, P=0.0137). ROC curve analysis suggested that the area under the curve (AUC), sensitivity and specificity of BTLA RT-PCR detection were 0.6315, 53.57%, 57.69% while for BTLA+CD11c+ detection were 0.8039, 88.46% and 73.21% and for BTLA+CD68+ detection were 0.6973, 60.71% and 61.54%. Conclusions: BTLA is highly expressed in peripheral blood and specific cell types of patients with PTB and is correlated with specific clinical indicators, which may be an important molecular marker for the auxiliary diagnosis of PTB.

Assessment of CD27 expression on T-cells as a diagnostic and therapeutic tool for patients with smear-negative pulmonary tuberculosis.

BACKGROUND: There is a global focus on illness diagnosis in smear-negative and latent tuberculosis infectious populations (SN-TB and LTBI). CD27 has been suggested to play a direct role in active TB. Little is known about smear-negative individuals. Here, we tried to investigate whether it has a role in smear-negative populations. The expression of CD27 and MTB-specific CD27 in CD4+ T cells ("CD27-CD4+" and "CD27-IFN-γ+CD4+") was evaluated in MTB-unexposed controls (HC), TB contacts (TB-C) and SN-TB individuals by flow cytometry. The sensitivity, specificity and AUC (area under curve) of "CD27-IFN-γ+CD4+" cells to distinguish SN-TBs from HCs and TB-Cs were determined by receiver operating characteristic (ROC) curve analysis. The clinical index was selected from the clinical laboratory and evaluated for correlation with "CD27-IFN-γ+CD4+" cells by Spearman statistical analysis. RESULTS: We observed that the percentages of "CD27-IFN-γ+CD4+" cells were significantly increased in the SN-TB group compared with the HC and TB-C groups (AUC was 0.88, sensitivity was 82.14%, specificity was 80.00%, and P < 0.0001). The percentage of "CD27-IFN-γ+CD4+" cells was negatively correlated with WBC (white blood cell count) (r = - 0.3019, P = 0.0182) and positively correlated with IgE (immunoglobulin E) (r = 0.2805, P = 0.0362). Furthermore, "CD27-IFN-γ+CD4+" cells were significantly decreased, especially in the > 50 years group, after clinical treatment. CONCLUSION: The present results demonstrated that the percentage of "CD27-IFN-γ+CD4+" cells might be a conceivable molecular indicator in the diagnosis of SN-TB and was influenced by its outcome of therapy.

Mean platelet volume (MPV): new diagnostic indices for co-morbidity of tuberculosis and diabetes mellitus.

BACKGROUND: Tuberculosis (TB) and type 2 diabetes mellitus (DM) are global health diseases with high morbidity and mortality. Few studies have focused on platelet indices in TB-DM coinfection patients. The objective of this work was to analyze the platelet indices in TB, DM and TB-DM patients to assess the predictive value of the platelet index for the risk of these diseases. METHODS: In total, 246 patients admitted to our hospital were distributed into three groups (113 TB, 59 DM and 74 TB + DM). A total of 133 individuals were also recruited as healthy controls (HC). Platelet indices, namely, platelet count (PC), mean platelet volume (MPV), plateletcrit (PCT) and platelet distribution width (PDW), were compared among the four groups, and the relationship with inflammatory markers was explored by using statistical software. RESULTS: Our study discovered that MPV and PCT were significantly downregulated in TB + DM patients (9.95 ± 1.25 fL, 0.20 ± 0.05%, P < 0.0001, P = 0.0121, separately) compared with DM individuals (10.92 ± 1.17 fL, 0.22 ± 0.04%). Moreover, the changes in MPV were significantly higher in TB + DM patients (9.95 ± 1.25 fL, P = 0.0041) than in TB patients (9.42 ± 1.01 fL). No differences were found in PLT and PDW among the four groups (P > 0.05). The sensitivity and specificity of MPV in the differential diagnosis of DM patients vs TB + DM patients were 64.9 and 66.1% (P < 0.0001), respectively, and the sensitivity and specificity of MPV between TB patients and TB + DM patients was 60.8 and 66.4%, respectively (P = 0.003). MPV improved the diagnosis sensitivity when it was combined with clinical parameters, such as fasting blood glucose in DM and Mycobacterium tuberculosis culture result in TB (76.3% vs 64.9, 72.6% vs 60.8%, P < 0.0001, P = 0.001, respectively). In addition, the sensitivity and specificity of PCT in the differential diagnosis of DM patients vs TB + DM patients were 69.5 and 59.4%, respectively (P = 0.008). PCT improved the diagnosis sensitivity when combined with fasting blood glucose in DM (72.9% vs 64.9%, P = 0.004). In addition, MPV was linked to CRP (C-reactive protein) and ESR (erythrocyte sedimentation rate) in the TB + DM patients (r = 0.3203, P = 0.0054, r = 0.2504, P = 0.0307) but PCT was not (r = 0.1905, r = 0.008675, P > 0.05, respectively). CONCLUSIONS: Our research shows that MPV and PCT might be good clinical laboratory markers to distinguish TB + DM patients from TB or DM individuals, thus providing support for earlier clinical diagnosis, prevention, and therapy.

Electrochemical Desulfurative Cyclization Accessing Oxazol-2-amine Derivatives via Intermolecular C-N/C-O Bond Formation.

A practical protocol has been established to access diverse oxazol-2-amine derivatives in one step via the electrochemical desulfurative cyclization of isothiocyanates and α-amino ketones. On the basis of the cycle of in situ generation of iodine/desulfurative cyclization/iodide anion regeneration, the reaction is performed under metal-free and external-oxidant-free electrolytic conditions to achieve the formation of intermolecular C-O and C-N bonds, providing oxazol-2-amines in moderate to excellent yields.

A Tumor-Specific Super-Enhancer Drives Immune Evasion by Guiding Synchronous Expression of PD-L1 and PD-L2.

PD-L1 and PD-L2 are important targets for immune checkpoint blockade, but how tumor cells achieve their expression remains to be addressed. Here, we find that PD-L1 and PD-L2 are co-expressed in cancer cell lines and tissues across different cancer types. In breast cancer, MDA-MB-231 and SUM-159 cells show high expression of both PD-L1 and PD-L2. The expression of both PD-L1 and PD-L2 is greatly reduced upon treatment of inhibitors of super-enhancers. Bioinformatic analysis identifies a potential super-enhancer (PD-L1L2-SE) that is located between the CD274 and CD273 genes. Genetic deletion of PD-L1L2-SE profoundly reduces the expression of PD-L1 and PD-L2. PD-L1L2-SE-deficient cancer cells fail to generate immune evasion and are sensitive to T cell-mediated killing. Notably, epigenetic activation of such a region (PD-L1L2-SE) is correlated with PD-L1 and PD-L2. Taken together, we identify a super-enhancer (PD-L1L2-SE) that is responsible for the overexpression of PD-L1 and PD-L2 as well as immune evasion in cancer.

Electrochemical vicinal aminotrifluoromethylation of alkenes: high regioselective acquisition of ß-trifluoromethylamines.

A novel vicinal aminotrifluoromethylation of alkenes using CF3SO2Na as a trifluoromethyl precursor and acetonitrile as an N-nucleophile has been achieved by an electrooxidative strategy. The present electrochemical protocol achieves efficient and highly regioselective difunctionalization of C[double bond, length as m-dash]C bonds under metal-free and external oxidant-free electrolysis conditions, leading to a series of ß-trifluoromethylamine compounds with good to excellent yields. It is confirmed that the reaction involves free radical processes since CF3 radicals are trapped by scavengers and the ß-trifluoromethylated radical is trapped by BHT, and the deuterium-labeling experiments prove that the oxygen in the product comes from water.

miR­145 suppresses ovarian cancer progression via modulation of cell growth and invasion by targeting CCND2 and E2F3.

MicroRNAs (miRNA/miRs) have been demonstrated to be critical post­transcriptional modulators of gene expression during tumorigenesis. Numerous miRNAs have been revealed to be downregulated in human epithelial ovarian cancer (EOC). In the present study, it was observed that the expression of miR­145 was decreased in EOC tissues and cell lines. Overexpression of miR­145 inhibited the proliferation, migration and invasion of EOC cells. The D­type cyclin 2, cyclin D2 (CCND2), and E2F transcription factor 3 (E2F3) were confirmed to be targets of miR­145. In addition, restoration of these 2 genes significantly reversed the tumor suppressive effects of miR­145. Collectively, the results indicated that miR­145 serves a critical role in suppressing the biological behavior of EOC cells by targeting CCND2 and E2F3. Therefore, miR­145 was suggested to be a potential miRNA­based therapeutic target in ovarian cancer.

Comprehensive transcriptome profiling in elderly cancer patients reveals aging-altered immune cells and immune checkpoints.

Aging is the single most significant risk factor for cancer development. However, the potential impact of aging on cancer microenvironment remains poorly understood. Here, we performed a pan-cancer transcriptome analysis to identify aging-specific molecular patterns across 18 cancer types. Strikingly, aging-specific molecular features define human cancers into two types, including the strong and weak aging-effect groups. Significant aging associated molecular signature was observed in 16 cancer types (strong aging-effect group) such as breast invasive carcinoma and acute myeloid leukemia. In such 16 cancer types, old patients showed obvious poor survival compared to young patients, but this observation was not found in the weak aging-effect cancers. Aging-associated cancer-relevant molecules significantly enriched in 23 pathways including EMT and KRAS signaling. More interestingly, in cancer microenvironment, aging significantly restrains adaptive immunity, but strikingly, increases the number of infiltrated innate immune cells. Further analysis shows that the expression of immune checkpoints including PD-1, PD-L1, PD-L2 and CTLA-4 are mostly correlated with age. In general, cancer cells in elderly patients show a more aggressive phenotype and their surrounding microenvironment is under a more immune suppression status compared to young patients. Our study provides a systematic understanding of aging-associated molecular features in pan-cancer and indicates a clinical requirement to develop aging-specific therapeutic strategies in a majority of cancer types. Furthermore, aging-altered immune cells and immune checkpoints should be considered in cancer immunotherapy.

Antibody Modified Nanoparticle-Mediated Delivery of miR-124 Regulates Apoptosis via Repression the Stat3 Signal in Mycobacterial-Infected Microglia.

The mechanism of Mycobacterium tuberculosis (M.tb) evasion of host cell remains elusive. Several microRNAs that are involved in this complex process were identified. miRNA interference-based therapeutics represents an attractive challenge and shows huge potential for disorder treatment. In this study, we found that miR-124-3p expression is significantly decreased in microglia after Mycobacterium marinum (M.m) infection. To achieve better target transfection effect, a CD11b antibody and PEI modified nanoparticles-based Nano platform had been developed. This system was equipped by conjugation of miRNA-124-3p onto the surface of nanoparticles with a PEI/CD11b antibody coating. Transfection with miR-124-3p promoted microglia apoptosis through upregulation of Caspase3 or downregulation of Bcl-2 and Bcl-xl. More importantly, transfection with miR-124-3p inhibitor increases the mycobacterium proliferation in microglia. Based on the above, we further found miRNA-124-3p to bind to 3'untranslated region of Stat3, resulting in the downregulation of its protein to trigger cells apoptosis through Stat3-related pathway. As such, our research might provide new insights towards target delivering miRNA through the bold-brain barrier (BBB) and exploiting highly effective anti-tuberculous meningitis drugs. Taken together, our findings suggest how Mycobacterium can manipulate host miRNA expression to regulate cell survival for its own proliferation, and highlight the importance to develop novel therapeutic strategies against tuberculous meningitis.

Inhibition of microRNA-155 modulates endotoxin tolerance by upregulating suppressor of cytokine signaling 1 in microglia.

Endotoxin tolerance is an immunohomeostatic reaction to reiterant lipopolysaccharide (LPS) exposure that maintains a state of altered responsiveness in immune cells, resulting in the inhibition of the pro-inflammatory response and the resolution of inflammation. Microglia constitutes the first line of defense against endogenous and external challenges in the brain. MicroRNAs (miRs) serve a critical function in the regulation of inflammation. The aim of the present study was to investigate whether miR-155 regulates endotoxin tolerance. miR-155 and suppressor of cytokine signaling-1 (SOCS1) mRNA expression was measured using RT-qPCR. The expression of SOCS1 was measured by western blotting and immunofluorescence. TNF-α levels were detected by an enzyme-linked immunosorbent assay. The results indicated that miR-155 expression was significantly downregulated in the microglia and cortex tissue following the induction of endotoxin tolerance. This was consistent with an increase in the expression of SOCS1, a predicted target of miR-155 and key inhibitor of the inflammatory reaction. Transfection with miR-155 inhibitor significantly enhanced SOCS1 expression in the microglia following the induction of endotoxin tolerance. SOCS1 knockdown using short hairpin RNA partly inhibited the anti-inflammatory process and promoted the inflammatory response during endotoxin tolerance. The results of the current study indicate that miR-155 inhibition contributes to the development of endotoxin tolerance. Understanding how miRs regulate inflammatory mechanisms may facilitate the development of novel therapeutic strategies to treat CNS disorders.

Mycobacterium marinum Infection in Zebrafish and Microglia Imitates the Early Stage of Tuberculous Meningitis.

Mycobacterium tuberculosis (M. tuberculosis) invading and activating microglia causes the most serious subtypes of tuberculosis called tubercular meningitis. However, the developmental process of tubercular meningitis, especially the early phase, is poorly understood due to lacking well-established and well-accepted visible models in vitro and in vivo. Here, consistent with one recent report, we found Mycobacterium marinum (M. marinum) invade the zebrafish brain and subsequently cause granuloma-like structures. We further showed that M. marinum, which shares similar characteristics with M. tuberculosis, can invade microglia and replicate in microglia, which subsequently promote the secretion of pro-inflammatory cytokines such as IL-1ß, IL-6, and TNF-α. M. marinum infection in microglia can also promote autophagy, which conversely limits the replication of M. marinum. Thus, pharmacological activation of autophagy by rapamycin could prevent M. marinum replication. Our study provides in vivo and in vitro models to study underlying pathogenic mechanisms of tubercular meningitis by using M. marinum. Our results also showed that activation of autophagy could be a meaningful way to prevent tubercular meningitis.

Identification and characterization of PP2C phosphatase SjPtc1 in Schistosoma japonicum.

Protein phosphorylation, regulated by protein kinases and protein phosphatases, is crucial for protein structure and function in eukaryotic organisms. Type 2C protein phosphatase (PP2C) belongs to the serine/threonine phosphatase family and its activities require the presence of a divalent magnesium or manganese ion. In the present study, a potential PP2C phosphatase (SjPtc1) was identified in Schistosoma japonicum. The SjPTC1 gene was found to be highly expressed in adult worms. A recombinant SjPtc1 protein showed typical PP2C phosphatase activity. Heterologous SjPTC1 expression reversed the sensitivity of yeast ptc1 null mutants toward H2O2, ZnCl2, cisplatin, and rapamycin. Collectively, the results suggest that SjPtc1 may take part in the regulation of cellular responses to oxidative stress, DNA damage stress, and the TOR (target of rapamycin) signaling pathway.

The N-terminal pY33XL motif of CaPsy2 is critical for the function of protein phosphatase 4 in CaRad53 deactivation, DNA damage-induced filamentation and virulence in Candida albicans.

Protein phosphatase PP4 is composed of one catalytic subunit and one or two regulatory subunits and conserved in eukaryotic cells. The catalytic subunit CaPph3 forms a complex with the regulatory subunit CaPsy2, which dephosphorylates activated CaRad53 during adaptation to and recovery from MMS-mediated DNA damage. We show here that the N-terminal Y33A mutation of CaPsy2 blocks the interaction between CaPph3 and CaRad53, the deactivation of CaRad53 and the morphologic switch in recovery from genotoxic stress. In Saccharomyces cerevisiae, the ScPph3-ScPsy2-ScPsy4 complex functions to dephosphorylate γH2A. In this study, we show that CaPsy4 is a functional homolog of ScPsy4 and not involved in the deactivation of CaRad53 or CaHta, the ortholog of H2A. However, deletion of CaPSY4 causes C. albicans cells a sensitivity to genotoxic reagents and a defect in DNA damage-induced filamentation. CaPsy4 interacts with both CaPph3 and CaPsy2, but the function of CaPsy4 is independent of CaPph3 and CaPsy2 in response to genotoxic stress. C. albicans cells lacking CaPPH3, CaPSY2 or CaPSY4, and C. albicans cells carrying the Y33A mutation of CaPSY2, show increased virulence to mice. Therefore, PP4 plays a negative role in regulating the DNA damage-induced filamentation and the virulence in C. albicans.