Plant Homeodomain Finger Protein 8 Research Articles

PHF8-GLUL axis in lipid deposition and tumor growth of clear cell renal cell carcinoma.

For clear cell renal cell carcinoma (ccRCC), lipid deposition plays important roles in the development, metastasis, and drug resistance. However, the molecular mechanisms underlying lipid deposition in ccRCC remain largely unknown. By conducting an unbiased CRISPR-Cas9 screening, we identified the epigenetic regulator plant homeodomain finger protein 8 (PHF8) as an important regulator in ccRCC lipid deposition. Moreover, PHF8 is regulated by von Hippel-Lindau (VHL)/hypoxia-inducible factor (HIF) axis and essential for VHL deficiency-induced lipid deposition. PHF8 transcriptionally up-regulates glutamate-ammonia ligase (GLUL), which promotes the lipid deposition and ccRCC progression. Mechanistically, by forming a complex with c-MYC, PHF8 up-regulates TEA domain transcription factor 1 (TEAD1) in a histone demethylation-dependent manner. Subsequently, TEAD1 up-regulates GLUL transcriptionally. Pharmacological inhibition of GLUL by l-methionine sulfoximine not only repressed ccRCC lipid deposition and tumor growth but also enhanced the anticancer effects of everolimus. Thus, the PHF8-GLUL axis represents a potential therapeutic target for ccRCC treatment.

Histone demethylase PHF8 facilitates the development of chronic myeloid leukaemia by directly targeting BCR::ABL1.

Although tyrosine kinase inhibitors (TKIs) have revolutionized the treatment of chronic myeloid leukaemia (CML), TKI resistance remains a major challenge. Here, we demonstrated that plant homeodomain finger protein 8 (PHF8), a histone demethylase was aberrantly enriched in CML samples compared to healthy controls. PHF8 inhibited CML cell differentiation and promoted CML cell proliferation. Furthermore, the proliferation-inhibited function of PHF8-knockdown have stronger effect on imatinib mesylate (IM)-resistant CML cells. Mechanistically, we identified that PHF8 as a transcriptional modulator interacted with the promoter of the BCR::ABL1 fusion gene and alters the methylation levels of H3K9me1, H3K9me2 and H3K27me1, thereby promoting BCR::ABL1 transcription. Overall, our study suggests that targeting PHF8, which directly regulates BCR::ABL1 expression, is a useful therapeutic approach for CML.

Effect of ribose-glycated BSA on histone demethylation.

A reducing sugar reacts with the protein, resulting in advanced glycation end-products (AGEs), which have been implicated in diabetes-related complications. Recently, it has been found that both type 1 and type 2 diabetic patients suffer from not only glucose but also ribose dysmetabolism. Here, we compared the effects of ribose and glucose glycation on epigenetics, such as histone methylation and demethylation. To prepare ribose-glycated (riboglycated) proteins, we incubated 150 μM bovine serum albumin (BSA) with 1 M ribose at different time periods, and we evaluated the samples by ELISAs, Western blot analysis, and cellular experiments. Riboglycated BSA, which was incubated with ribose for approximately 7 days, showed the strongest cytotoxicity, leading to a significant decrease in the viability of SH-SY5Y cells cultured for 24 h (IC50 = 1.5 μM). A global demethylation of histone 3 (H3K4) was observed in SH-SY5Y cells accompanied with significant increases in lysine-specific demethylase-1 (LSD1) and plant homeodomain finger protein 8 (PHF8) after treatment with riboglycated BSA (1.5 μM), but demethylation did not occur after treatment with glucose-glycated (glucoglycated) proteins or the ribose, glucose, BSA, and Tris–HCl controls. Moreover, a significant demethylation of H3K4, H3K4me3, and H3K4me2, but not H3K4me1, occurred in the presence of riboglycated proteins. A significant increase of formaldehyde was also detected in the medium of SH-SY5Y cells cultured with riboglycated BSA, further indicating the occurrence of histone demethylation. The present study provides a new insight into understanding an epigenetic mechanism of diabetes mellitus (DM) related to ribose metabolic disorders.

The histone demethylase PHF8 regulates TGFβ signaling and promotes melanoma metastasis.

The contribution of epigenetic dysregulation to metastasis remains understudied. Through a meta-analysis of gene expression datasets followed by a mini-screen, we identified Plant Homeodomain Finger protein 8 (PHF8), a histone demethylase of the Jumonji C protein family, as a previously unidentified prometastatic gene in melanoma. Loss- and gain-of-function approaches demonstrate that PHF8 promotes cell invasion without affecting proliferation in vitro and increases dissemination but not subcutaneous tumor growth in vivo, thus supporting its specific contribution to the acquisition of metastatic potential. PHF8 requires its histone demethylase activity to enhance melanoma cell invasion. Transcriptomic and epigenomic analyses revealed that PHF8 orchestrates a molecular program that directly controls the TGFβ signaling pathway and, as a consequence, melanoma invasion and metastasis. Our findings bring a mechanistic understanding of epigenetic regulation of metastatic fitness in cancer, which may pave the way for improved therapeutic interventions.

The role of PHF8 and TLR4 in osteogenic differentiation of periodontal ligament cells in inflammatory environment.

Histone methylation is considered to play an important role in the occurrence and development of periodontitis. Plant homeodomain finger protein 8 (PHF8), a histone demethylase, has been shown to regulate inflammation and osteogenic differentiation of bone marrow stromal cells (BMSCs). This study aimed to detect the functions of PHF8 and TLR4 in osteogenic differentiation in an inflammatory environment induced by Porphyromonas gingivalis lipopolysaccharide (Pg-LPS) METHODS: A periodontitis mouse model was established, and the mice were treated with TAK-242. Immunohistochemical staining was used to detect the expression of PHF8 in periodontal tissue. Periodontal ligament cells (PDLCs) were treated with mineralization induction medium supplemented with Pg-LPS and/or TAK-242, and a Cell Counting Kit-8 (CCK-8) assay was used to detect the proliferation of PDLCs. Real-time PCR and western blotting were used to detect the mRNA and protein expression levels, respectively, of PHF8, toll-like receptor 4 (TLR4) and the other osteogenic markers alkaline phosphatase (ALP), osteocalcin (OCN), Special AT-rich sequence-binding protein 2 (Satb2) and Runt-related transcription factor 2 (Runx2) RESULTS: Periodontitis reduced PHF8 expression in periodontal tissue, and TAK-242 partially reversed this downregulation. An in vitro experiment revealed that the mRNA and protein expression levels of PHF8 were significantly upregulated during the osteogenic differentiation of PDLCs. Alizarin red staining showed that the mineralized nodules of PDLCs in osteogenic induction group were more than those in control group. Real-time PCR and western blot results indicated that Pg-LPS inhibited PHF8 expression and upregulated TLR4 expression in PDLCs. TAK-242 inhibited TLR4 and partially reversed the inhibition of PHF8 expression and osteogenic differentiation induced by Pg-LPS in PDLCs CONCLUSION: PHF8 and TLR4 play important roles in periodontitis. Pg-LPS inhibits the expression of PHF8 via upregulation of TLR4 and might further inhibit the osteogenic differentiation of PDLCs. However, the specific mechanisms involved remain to be explored.

MYC Regulates PHF8, Which Promotes the Progression of Gastric Cancer by Suppressing miR-22-3p.

Plant homeodomain finger protein 8 (PHF8) has been reported to participate in cancer development and metastasis of various types of tumors. However, little is known about the functional mechanism of PHF8 in gastric cancer (GC). This study aimed to explore the PHF8 expression pattern and function, and the role of the MYC/miRNA/PHF8 axis in GC. PHF8 expression was upregulated in GC tissues and cells as measured using quantitative reverse transcription polymerase chain reaction and western blotting. PHF8 knockdown suppressed the proliferation, migration, and invasion of GC cells, as determined using the CCK-8 assay and Transwell assay. MicroRNA-22-3p targeted PHF8, as verified by a dual-luciferase reporter assay. MYC upregulated the protein expression of PHF8 but had no effect on PHF8 mRNA expression. MYC regulates PHF8 by affecting the stability of miR-22-3p. We identified a novel MYC/miR-22-3p/PHF8 regulatory axis in GC. Therefore, PHF8 may provide a new therapeutic target for patients with GC.

PHF8 Plays an Oncogene Function in Hepatocellular Carcinoma Formation.

Hepatocellular carcinoma (HCC) has high morbidity and mortality rates, and the number of new cases and deaths from liver cancer are increasing. However, the details of the regulation in HCC remain largely unknown. Plant homeodomain finger protein 8 (PHF8) is a JmjC domain-containing protein. Recently, PHF8 was reported to participate in several types of cancer. However, the biological function and clinical significance of PHF8 in HCC remain unknown. In this study, we investigate the role of PHF8 in HCC growth and metastasis. We used bioinformatics analysis and identified the differentially expressed PHF8 in primary HCC and metastasis HCC. Immunohistochemistry analysis demonstrated that PHF8 was expressed higher in human HCC tissues than in corresponding adjacent noncancerous tissues. Silencing PHF8 in HCC cells significantly decreased the cells’ ability of proliferation, migration, invasion, and sphere formation. On the contrary, overexpression of PHF8 promoted these properties. In addition, the analysis in vivo showed that PHF8 overexpression promoted tumor formation and metastasis in nude mice. In the end, the RNA-sequence assay showed that CUL4A is upregulated by the PHF8. Taken together, these results demonstrated that PHF8 was a novel oncogene in HCC, which may contribute to therapeutic approaches aimed at targeting components of the PHF8 and provide new insights into the mechanisms governing the developmental programs in HCC.

Short-Term Mitochondrial Permeability Transition Pore Opening Modulates Histone Lysine Methylation at the Early Phase of Somatic Cell Reprogramming

Reprogramming of somatic cells to induced pluripotent stem cells reconfigures chromatin modifications. Whether and how this process is regulated by signals originating in the mitochondria remain unknown. Here we show that the mitochondrial permeability transition pore (mPTP), a key regulator of mitochondrial homeostasis, undergoes short-term opening during the early phase of reprogramming and that this transient activation enhances reprogramming. In mouse embryonic fibroblasts, greater mPTP opening correlates with higher reprogramming efficiency. The reprogramming-promoting function of mPTP opening is mediated by plant homeodomain finger protein 8 (PHF8) demethylation of H3K9me2 and H3K27me3, leading to reduction in their occupancies at the promoter regions of pluripotency genes. mPTP opening increases PHF8 protein levels downstream of mitochondrial reactive oxygen species production and miR-101c and simultaneously elevates levels of PHF8's cofactor, α-ketoglutarate. Our findings represent a novel mitochondria-to-nucleus pathway in cell fate determination by mPTP-mediated epigenetic regulation.

The Histone Demethylase PHF8 Is Essential for Endothelial Cell Migration

Epigenetic marks critically control gene expression and thus the cellular activity state. The functions of many epigenetic modifiers in the vascular system have not yet been studied. We screened for histone modifiers in endothelial cells and observed a fairly high expression of the histone plant homeodomain finger protein 8 (PHF8). Given its high expression, we hypothesize that this histone demethylase is important for endothelial cell function. Overexpression of PHF8 catalyzed the removal of methyl-groups from histone 3 lysine 9 (H3K9) and H4K20, whereas knockdown of the enzyme increased H3K9 methylation. Knockdown of PHF8 by RNAi also attenuated endothelial proliferation and survival. As a functional readout endothelial migration and tube formation was studied. PHF8 siRNA attenuated the capacity for migration and developing of capillary-like structures. Given the impact of PHF8 on cell cycle genes, endothelial E2F transcription factors were screened, which led to the identification of the gene repressor E2F4 to be controlled by PHF8. Importantly, PHF8 maintains E2F4 but not E2F1 expression in endothelial cells. Consistently, chromatin immunoprecipitation revealed that PHF8 reduces the H3K9me2 level at the E2F4 transcriptional start site, demonstrating a direct function of PHF8 in endothelial E2F4 gene regulation. Conclusion: PHF8 by controlling E2F4 expression maintains endothelial function.

The histone demethylase PHF8 promotes prostate cancer cell growth by activating the oncomiR miR-125b.

AimsProstate cancer (PCa) is the most frequently diagnosed malignancy in men. However, the underlying mechanism is not fully understood. In this study, we aim to research the molecular mechanisms underlying the initiation and progression of PCa.ResultsPlant homeodomain finger protein 8 (PHF8) is upregulated in human PCa tissues and cell lines. PHF8 knockdown attenuates growth and cellular transformation of PCa cells. PHF8 depletion induces PCa cell apoptosis by activating proapoptotic proteins and inactivating antiapoptotic proteins. Furthermore, miR-125b is a target of PHF8, and miR-125b seems to be essential for the hyper proliferation of PCa cells in the presence of PHF8.ConclusionIn conclusion, we identify the histone demethylase PHF8 as an oncogenic protein in human PCa. These findings indicate PHF8 as a potential candidate for clinical intervention.

Oncogenic Features of PHF8 Histone Demethylase in Esophageal Squamous Cell Carcinoma

Esophageal cancer is the sixth leading cause of cancer-related deaths worldwide. It has been reported that histone demethylases are involved in the carcinogenesis of certain types of tumors. Here, we studied the role of one of the histone lysine demethylases, plant homeodomain finger protein 8 (PHF8), in the carcinogenesis of esophageal squamous cell carcinoma (ESCC). Using short hairpin RNA via lentiviral infection, we established stable ESCC cell lines with constitutive downregulation of PHF8 expression. Knockdown of PHF8 in ESCC cells resulted in inhibition of cell proliferation and an increase of apoptosis. Moreover, there were reductions of both anchorage-dependent and -independent colony formation. In vitro migration and invasion assays showed that knockdown of PHF8 led to a reduction in the number of migratory and invasive cells. Furthermore, downregulation of PHF8 attenuated the tumorigenicity of ESCC cells in vivo. Taken together, our study revealed the oncogenic features of PHF8 in ESCC, suggesting that PHF8 may be a potential diagnostic marker and therapeutic target for ESCC.

The Histone Demethylase PHF8 and Neural Development*

PHF8(PHD finger protein 8) is a Fe2+ and 2-oxoglutarate dependent histone lysine demethylase and belongs to a family of JmjC domain-containing proteins.PHF8 also contains a plant homeodomain(PHD) finger motif in its N-terminus,which involves in transcriptional regulation.PHF8 can demethylate H3K9me2/1,H4K20me1 and H3K27me2 with JmjC domain,and also act as a transcriptional coactivator through binding to H3K4me3 via PHD finger.PHF8 regulates expression of rRNA and many protein-coding genes involved in neural development such as JARID1C.Mutations in human PHF8 which are defective in histone demethylase activity can cause inherited X-linked mental retardation(XLMR) and cleft lip/cleft palate.These researches suggested that PHF8 is an important regulator of neural development,which deepens the understanding of histone methylation with gene expression and provides novel clues to understanding of XLMR.

Structural insights into a novel histone demethylase PHF8

Dynamic regulation of histone methylation/demethylation plays an important role during development. Mutations and truncations in human plant homeodomain (PHD) finger protein 8 (PHF8) are associated with X-linked mental retardation and facial anomalies, such as a long face, broad nasal tip, cleft lip/cleft palate and large hands, yet its molecular function and structural basis remain unclear. Here, we report the crystal structures of the catalytic core of PHF8 with or without alpha-ketoglutarate (alpha-KG) at high resolution. Biochemical and structural studies reveal that PHF8 is a novel histone demethylase specific for di- and mono-methylated histone H3 lysine 9 (H3K9me2/1), but not for H3K9me3. Our analyses also reveal how human PHF8 discriminates between methylation states and achieves sequence specificity for methylated H3K9. The in vitro demethylation assay also showed that the F279S mutant observed in clinical patients possesses no demethylation activity, suggesting that loss of enzymatic activity is crucial for pathogenesis of PHF8 patients. Taken together, these results will shed light on the molecular mechanism underlying PHF8-associated developmental and neurological diseases.

Autism‐associated familial microdeletion of Xp11.22

We describe two brothers with autistic disorder, intellectual disability (ID) and cleft lip/palate with a microdeletion of Xp11.22 detected through screening individuals with autism spectrum disorders (ASDs) for microdeletions and duplications using 1-Mb resolution array comparative genomic hybridization. The deletion was confirmed by fluorescence in situ hybridization/real-time quantitative polymerase chain reaction (RT-qPCR) and shown to be inherited from their unaffected mother who had skewed (100%) X inactivation of the aberrant chromosome. RT-qPCR characterization of the del(X)(p11.22) region ( approximately 53,887,000-54,359,000 bp) revealed complete deletion of the plant homeodomain finger protein 8 (PHF8) gene as well as deletions of the FAM120C and WNK lysine-deficient protein kinase 3 (WNK3) genes, for which a definitive phenotype has not been previously characterized. Xp11.2 is a gene-rich region within the critical linkage interval for several neurodevelopmental disorders. Rare interstitial microdeletions of Xp11.22 have been recognized with ID, craniofacial dysmorphism and/or cleft lip/palate and truncating mutations of the PHF8 gene within this region. Despite evidence implicating genes within Xp11.22 with language and cognitive development that could contribute to an ASD phenotype, their involvement with autism has not been systematically evaluated. Population screening of 481 (319 males/81 females) and 282 X chromosomes (90 males/96 females) in respective ASD and control cohorts did not identify additional subjects carrying this deletion. Our findings show that in addition to point mutations, a complete deletion of the PHF8 gene is associated with the X-linked mental retardation Siderius-Hamel syndrome (OMIM 300263) and further suggest that the larger size of the Xp11.22 deletion including genes FAM120C and WNK3 may be involved in the pathogenesis of autism.

A novel mutation in the PHF8 gene is associated with X‐linked mental retardation with cleft lip/cleft palate

Recently, two truncating mutations in the PHF8 (plant homeodomain finger protein 8) gene have been found to cause X-linked mental retardation associated with cleft lip/cleft palate (CL/P). One of the truncating mutations was found in the original family with Siderius-Hamel CL/P syndrome where only two of the three affected individuals had mental retardation (MR) with CL/P and one individual had mild MR. The second mutation was present in a family with four affected men, three of whom had MR and CL/P, while the fourth individual had mild MR without clefting. Here, we report a novel nonsense mutation (p.K177X) in a male patient who has MR associated with CL/P. The mutation results in a truncated PHF8 protein lacking the Jumonji-like C terminus domain and five nuclear localization signals. Our finding further supports the hypothesis that the PHF8 protein may play an important role in cognitive function and midline formation.