Inhibitor Of Growth 5 Research Articles

ING5 inhibits aerobic glycolysis of lung cancer cells by promoting TIE1-mediated phosphorylation of pyruvate dehydrogenase kinase 1 at Y163.

Aerobic glycolysis is critical for tumor growth and metastasis. Previously, we have found that the overexpression of the inhibitor of growth 5 (ING5) inhibits lung cancer aggressiveness and epithelial-mesenchymal transition (EMT). However, whether ING5 regulates lung cancer metabolism reprogramming remains unknown. Here, by quantitative proteomics, we showed that ING5 differentially regulates protein phosphorylation and identified a new site (Y163) of the key glycolytic enzyme PDK1 whose phosphorylation was upregulated 13.847-fold. By clinical study, decreased p-PDK1Y163 was observed in lung cancer tissues and correlated with poor survival. p-PDK1Y163 represents the negative regulatory mechanism of PDK1 by causing PDHA1 dephosphorylation and activation, leading to switching from glycolysis to oxidative phosphorylation, with increasing oxygen consumption and decreasing lactate production. These effects could be impaired by PDK1Y163F mutation, which also impaired the inhibitory effects of ING5 on cancer cell EMT and invasiveness. Mouse xenograft models confirmed the indispensable role of p-PDK1Y163 in ING5-inhibited tumor growth and metastasis. By siRNA screening, ING5-upregulated TIE1 was identified as the upstream tyrosine protein kinase targeting PDK1Y163. TIE1 knockdown induced the dephosphorylation of PDK1Y163 and increased the migration and invasion of lung cancer cells. Collectively, ING5 overexpression-upregulated TIE1 phosphorylates PDK1Y163, which is critical for the inhibition of aerobic glycolysis and invasiveness of lung cancer cells.

The Antitumor and Sorafenib-resistant Reversal Effects of Ursolic Acid on Hepatocellular Carcinoma via Targeting ING5.

Inhibitor of growth 5 (ING5) has been reported to be involved in the malignant progression of cancers. Ursolic acid (UA) has shown remarkable antitumor effects. However, its antitumor mechanisms regarding of ING5 in hepatocellular carcinoma (HCC) remain unclear. Herein, we found that UA significantly suppressed the proliferation, anti-apoptosis, migration and invasion of HCC cells. In addition, ING5 expression in HCC cells treated with UA was obviously downregulated in a concentration- and time-dependent manner. Additionally, the pro-oncogenic role of ING5 was confirmed in HCC cells. Further investigation revealed that UA exerted antitumor effects on HCC by inhibiting ING5-mediated activation of PI3K/Akt pathway. Notably, UA could also reverse sorafenib resistance of HCC cells by suppressing the ING5-ACC1/ACLY-lipid droplets (LDs) axis. UA abrogated ING5 transcription and downregulated its expression by reducing SRF and YY1 expression and the SRF-YY1 complex formation. Alb/JCPyV T antigen mice were used for in vivo experiments since T antigen upregulated ING5 expression by inhibiting the ubiquitin-mediated degradation and promoting the T antigen-SRF-YY1-ING5 complex-associated transcription. UA suppressed JCPyV T antigen-induced spontaneous HCC through inhibiting ING5-mediated PI3K/Akt signaling pathway. These findings suggest that UA has the dual antitumoral functions of inhibiting hepatocellular carcinogenesis and reversing sorafenib resistance of HCC cells through targeting ING5, which could serve as a potential therapeutic strategy for HCC.

Tctp, a unique Ing5-binding partner, inhibits the chromatin binding of Enok in Drosophila

The MOZ/MORF histone acetyltransferase complex is highly conserved in eukaryotes and controls transcription, development, and tumorigenesis. However, little is known about how its chromatin localization is regulated. Inhibitor of growth 5 (ING5) tumor suppressor is a subunit of the MOZ/MORF complex. Nevertheless, the invivo function of ING5 remains unclear. Here, we report an antagonistic interaction between Drosophila Translationally controlled tumor protein (TCTP) (Tctp) and ING5 (Ing5) required for chromatin localization of the MOZ/MORF (Enok) complex and H3K23 acetylation. Yeast two-hybrid screening using Tctp identified Ing5 as a unique binding partner. Invivo, Ing5 controlled differentiation and down-regulated epidermal growth factor receptor signaling, whereas it is required in the Yorkie (Yki) pathway to determine organ size. Ing5 and Enok mutants promoted tumor-like tissue overgrowth when combined with uncontrolled Yki activity. Tctp depletion rescued the abnormal phenotypes of the Ing5 mutation and increased the nuclear translocation of Ing5 and chromatin binding of Enok. Nonfunctional Enok promoted the nuclear translocation of Ing5 by reducing Tctp, indicating a feedback mechanism between Tctp, Ing5, and Enok to regulate histone acetylation. Therefore, Tctp is essential for H3K23 acetylation by controlling the nuclear translocation of Ing5 and chromatin localization of Enok, providing insights into the roles of human TCTP and ING5-MOZ/MORF in tumorigenesis.

BRPF1-KAT6A/KAT6B Complex: Molecular Structure, Biological Function and Human Disease.

Simple SummaryBRPF1 (also named as BR140) was identified 28 years ago, and it was not until the past 5 years that its mutations in humans caught increasing attention. Those patients with BRPF1 mutations often display intellectual disability or suffer from leukemia or medulloblastoma. BRPF1 is an activator and a scaffold protein of a multiunit complex, with other members being KAT6A/KAT6B, ING5 or ING4 and MEAF6. This review summarizes the molecular structure, biological function and human diseases associated with the BRPF1-KAT6A/KAT6B complex and summarizes the development of inhibitors for targeting specific domains of BRPF1.The bromodomain and PHD finger–containing protein1 (BRPF1) is a member of family IV of the bromodomain-containing proteins that participate in the post-translational modification of histones. It functions in the form of a tetrameric complex with a monocytic leukemia zinc finger protein (MOZ or KAT6A), MOZ-related factor (MORF or KAT6B) or HAT bound to ORC1 (HBO1 or KAT7) and two small non-catalytic proteins, the inhibitor of growth 5 (ING5) or the paralog ING4 and MYST/Esa1-associated factor 6 (MEAF6). Mounting studies have demonstrated that all the four core subunits play crucial roles in different biological processes across diverse species, such as embryonic development, forebrain development, skeletal patterning and hematopoiesis. BRPF1, KAT6A and KAT6B mutations were identified as the cause of neurodevelopmental disorders, leukemia, medulloblastoma and other types of cancer, with germline mutations associated with neurodevelopmental disorders displaying intellectual disability, and somatic variants associated with leukemia, medulloblastoma and other cancers. In this paper, we depict the molecular structures and biological functions of the BRPF1-KAT6A/KAT6B complex, summarize the variants of the complex related to neurodevelopmental disorders and cancers and discuss future research directions and therapeutic potentials.

LncRNA CASC2 inhibits hypoxia-induced pulmonary artery smooth muscle cell proliferation and migration by regulating the miR-222/ING5 axis

BackgroundPulmonary arterial hypertension (PAH) is often characterized by cell proliferation and migration of pulmonary arterial smooth muscle cells (PASMCs). LncRNA cancer susceptibility candidate 2 (CASC2) has been revealed to be involved in PASMC injury in hypoxia-induced pulmonary hypertension. However, the exact molecular mechanisms whereby CASC2 regulates PASMC proliferation and migration are still incompletely understood.MethodsThe expression levels of CASC2, miR-222 and inhibitor of growth 5 (ING5) were measured using quantitative real-time polymerase chain reaction (qRT-PCR) or western blot, respectively. Cell proliferation was analyzed by Cell Counting Kit-8 (CCK-8) assay. Wound healing assay was used to analyze cell migration ability. The relationship between miR-222 and CASC2 or ING5 was confirmed using bioinformatics analysis, luciferase reporter assay and RNA immunoprecipitation assay.ResultsCASC2 was down-regulated in hypoxia-induced PASMCs in a dose- and time-dependent manner. Functional experiments showed that CASC2 overexpression could reverse hypoxia-induced proliferation and migration of PASMCs. Bioinformatics analysis indicated that CASC2 acted as a competing endogenous RNA of miR-222, thereby regulating the expression of ING5, the downstream target of miR-222, in PASMCs. In addition, rescue assay suggested that the inhibition mediated by CASC2 of hypoxia-induced PASMC proliferation and migration could be attenuated by miR-222 inhibition or ING5 overexpression.ConclusionCASC2 attenuated hypoxia-induced PASMC proliferation and migration by regulating the miR-222/ING5 axis to prevent vascular remodeling and the development of PAH, providing a novel insight and therapeutic strategy for hypoxia-induced PAH.

Upregulation of miR-376c-3p alleviates oxygen\u2013glucose deprivation-induced cell injury by targeting ING5

BackgroundThe expression level of miR-376c-3p is significantly lower in infants with neonatal hypoxic-ischemic encephalopathy (HIE) than in healthy infants. However, the biological function of this microRNA remains largely elusive.MethodsWe used PC-12 and SH-SY5Y cells to establish an oxygen–glucose deprivation (OGD) cell injury model to mimic HIE in vitro. The miR-376c-3p expression levels were measured using quantitative reverse transcription PCR. The CCK-8 assay and flow cytometry were utilized to evaluate OGD-induced cell injury. The association between miR-376c-3p and inhibitor of growth 5 (ING5) was validated using the luciferase reporter assay. Western blotting was conducted to determine the protein expression of CDK4, cyclin D1, Bcl-2 and Bax.ResultsMiR-376c-3p was significantly downregulated in the OGD-induced cell injury model. Its overexpression elevated cell viability and impaired cell cycle G0/G1 phase arrest and apoptosis in PC-12 and SH-SY5Y cells after OGD. Downregulation of miR-376c-3p gave the opposite results. We further demonstrated that ING5 was a negatively regulated target gene of miR-376c-3p. Importantly, ING5 knockdown had a similar effect to miR-376c-3p-mediated protective effects against cell injury induced by OGD. Its overexpression abolished these protective effects.ConclusionOur data suggest that miR-376c-3p downregulated ING5 to exert protective effects against OGD-induced cell injury in PC-12 and SH-SY5Y cells. This might represent a novel therapeutic approach for neonatal HIE treatment.

ING5-mediated antineuroblastoma effects of suberoylanilide hydroxamic acid.

Neuroblastoma is the most common extracranial solid neuroendocrine cancer and is one of the leading causes of death in children. To improve clinical outcomes and prognosis, discovering new promising drugs and targeted medicine is essential. We found that applying Suberoylanilide hydroxamic acid (SAHA; Vorinostat, a histone deacetylase inhibitor) and MG132 (a proteasome inhibitor) to SH‐SY5Y cells synergistically suppressed proliferation, glucose metabolism, migration, and invasion and induced apoptosis and cell cycle arrest. These effects occurred both concentration and time dependently and were associated with the effects observed with inhibitor of growth 5 (ING5) overexpression. SAHA and MG132 treatment increased the expression levels of ING5, PTEN, p53, Caspase‐3, Bax, p21, and p27 but decreased the expression levels of 14‐3‐3, MMP‐2, MMP‐9, ADFP, Nanog, c‐myc, CyclinD1, CyclinB1, and Cdc25c concentration dependently, similar to ING5. SAHA may downregulate miR‐543 and miR‐196‐b expression to enhance the translation of ING5 protein, which promotes acetylation of histones H3 and H4. All three proteins (ING5 and acetylated histones H3 and H4) were recruited to the promoters of c‐myc, Nanog, CyclinD1, p21, and p27 for complex formation, thereby regulating the mRNA expression of downstream genes. ING5 overexpression and SAHA and/or MG132 administration inhibited tumor growth in SH‐SY5Y cells by suppressing proliferation and inducing apoptosis. The expression of acetylated histones H3 and ING5 may be closely linked to the tumor size of neuroblastomas. In summary, SAHA and/or MG132 can synergistically suppress the malignant phenotypes of neuroblastoma cells through the miRNA‐ING5‐histone acetylation axis and via proteasomal degradation, respectively. Therefore, the two drugs may serve as potential treatments for neuroblastoma.

ING5 inhibits cell proliferation and invasion in esophageal squamous cell carcinoma through regulation of the Akt/NF-κB/MMP-9 signaling pathway

The inhibitor of growth 5 (ING5) is a new candidate tumor suppressor gene (TSG) of the ING family. So far, there have been many reports about its functions related to cancer development. However, the biological roles of ING5 in esophageal squamous cell carcinoma (ESCC) remain unclear. In the present study, we demonstrated that ING5 was lowly expressed in ESCC tissues and cell lines. Overexpression of ING5 inhibited ESCC cell proliferation and invasion in vitro as well as suppressed tumor growth and metastasis in vivo. We also found that overexpression of ING5 significantly decreased the levels of p-AKT, NF-κB and MMP-9 in ECA109 cells. Taken together, these findings demonstrated that ING5 inhibited cell proliferation and invasion in ESCC through regulation of the Akt/NF-κB/MMP-9 signaling pathway. Thus, ING5 might be considered a promising target for ESCC treatment.

Overexpression of ING5 inhibits HGF-induced proliferation, invasion and EMT in thyroid cancer cells via regulation of the c-Met/PI3K/Akt signaling pathway

The inhibitor of growth 5 (ING5), a novel member of the ING family, is involved in diverse biological processes such as cell growth, apoptosis and DNA repair. Recently, ING5 has been reported to be associated with cancer development. However, its specific role in thyroid cancer has yet to be elucidated. In this study, we found that the expression of ING5 was significantly down-regulated in human thyroid cancer tissues and cell lines. In addition, overexpression of ING5 markedly inhibited hepatocyte growth factor (HGF)-induced proliferation, invasion and epithelial-mesenchymal transition (EMT) of thyroid cancer cells as well as suppressed the tumor growth and metastasis in vivo. Furthermore, our data showed that the c-Met/PI3K/Akt signaling pathway was responsible for the inhibitory effect of ING5 on the thyroid cancer. Taken together, these findings provided an essential basis for the tumor-suppression role of ING5 in thyroid cancer.

The miR-193a-3p-regulated ING5 gene activates the DNA damage response pathway and inhibits multi-chemoresistance in bladder cancer.

As the major barrier to curative cancer chemotherapy, chemoresistance presents a formidable challenge to both cancer researchers and clinicians. We have previously shown that the bladder cancer (BCa) cell line 5637 is significantly more sensitive to the cytoxicity of five chemotherapeutic agents than H-bc cells. Using an RNA-seq-based omic analysis and validation at both the mRNA and protein levels, we found that the inhibitor of growth 5 (ING5) gene was upregulated in 5637 cells compared with H-bc cells, indicating that it has an inhibitory role in BCa chemoresistance. siRNA-mediated inhibition of ING5 increased the chemoresistance and inhibited the DNA damage response pathway in 5637 cells. Conversely, forced expression of EGFP-ING5 decreased the chemoresistance of and activated the DNA damage response pathway in H-bc cells. We also showed that ING5 gene expression is inhibited by miR-193a-3p and is instrumental in miR-193a-3p's role in activating BCa chemoresistance. Our results demonstrate both the role and mechanism of inhibition of BCa chemoresistance by ING5.

EG-16 * ABERRANT Myst4/Brpf1 SIGNALING MISDIRECTS REGIONAL NEUROGENESIS PROGRAMS, SUSTAINING EXPRESSION OF SELF-RENEWAL GENES IN PEDIATRIC BRAIN CANCERS

The Myst family of acetyltransferase proteins has been shown to play important role in development and self-renewal, primarily through lysine acetylation on Histones H3 and H4. In neural development, Myst4 (Morf/KAT6B) has been found to be critical for self-renewal and for neuron generation in the developing nervous system and during adult neurogenesis. This chromatin modifier exists in a complex with Myst3 (Moz/KAT6A), the bromodomain factor Brpf1, which acts as a protein scaffold, targeting histone acetyltransferases to chromatin, as well as Inhibitor of Growth 5 (ING5) and Esa1-associated factor 6 (EAF6). Our laboratories have found alteration of these elements in pediatric brain cancers, suggesting a pathological role in abnormal neural progenitor growth. Exon-specific microarrays, DNA methylation studies and functional perturbation were performed to study the impact on tumor behavior. RNA interference in tumors and neural progenitors led to loss of H3K4acetylation in target genes and altered expression, including Spondin-1. Conversely, exogenous over-expression of targeting factors, such as Brpf1, enhanced expression of target genes, assessed by quantitative PCR analysis. Furthermore, expression of Myst3/4 and Brpf1 positively correlated with tumor malignancy markers in large patient cohorts, including Ki67, PCNA, and MELK, and with decreased overall survival. Assessment of direct functional relationships with tumor markers using ChIP-Seq approaches is currently being pursued to investigate direct Myst3/4/Brpf1-mediated promoter activity at known and novel target genes. These studies aim to elucidate the role of an important epigenetic mechanism in neurogenesis, the alteration of which may underlie global chromatin changes that contribute to tumor growth or initiation. Sustained progenitor growth may be suppressed by targeted therapies that disrupt these factors.

The MOZ Histone Acetyltransferase in Epigenetic Signaling and Disease

The monocytic leukemic zinc finger (MOZ) histone acetyltransferase (HAT) plays a role in acute myeloid leukemia (AML). It functions as a quaternary complex with the bromodomain PHD finger protein 1 (BRPF1), the human Esa1-associated factor 6 homolog (hEAF6), and the inhibitor of growth 5 (ING5). Each of these subunits contain chromatin reader domains that recognize specific post-translational modifications (PTMs) on histone tails, and this recognition directs the MOZ HAT complex to specific chromatin substrates. The structure and function of these epigenetic reader modules has now been elucidated, and a model describing how the cooperative action of these domains regulates HAT activity in response to the epigenetic landscape is proposed. The emerging role of epigenetic reader domains in disease, and their therapeutic potential for many types of cancer is also highlighted.

Molecular basis of histone acetyllysine recognition by the BRPF1 bromodomain (537.1)

Covalent modifications on histone tails play a key role in determining the outcome of many nuclear processes including transcription, DNA repair, recombination, and replication. In humans, translocation of the monocytic leukemia zinc finger (MOZ) histone acetyltransferase (HAT) complex has been linked to a subtype of acute myeloid leukemia (AML). MOZ forms tetrameric complexes with ING5 (inhibitor of growth 5), EAF6 (Esa1‐associated factor 6 ortholog), and the bromodomain‐PHD finger protein. BRPF proteins have been shown to bridge the association of MOZ with ING5 and EAF6. Deletion mapping studies have also revealed that the acetyltransferase domain of MOZ is sufficient for the interaction with BRPF1. BRPF proteins therefore play a key role in assembling and activating MOZ acetyltransferase complexes. BRPF1 contains a unique combination of domains typically found in chromatin‐associated factors, including PHD (plant homeodomain) fingers, a bromodomain and a PWWP (Pro‐Trp‐Trp‐Pro) domain. The bromodomain and PWWP domain of BRPF1 help recruit MOZ to distinct sites of active chromatin. Bromodomains are highly conserved motifs generally known to acetylated lysines on the histone tail, but the ligands recognized by BRPF1 bromodomain are currently unknown. In this study we identified the N‐terminal histone tail ligands for the BRPF1 bromodomain, characterized the protein‐ligand binding affinities and determined the functional importance of these interactions. We also used extensive molecular dynamics simulations to generate structural models of bromodomain‐histone ligand complexes, to analyze H‐bonding and other interactions, and to calculate the binding free energies. Our results outline the molecular mechanism driving binding specificity of the BRPF1 bromodomain for discrete acetyllysine residues on the N‐terminal histone tails. A better understanding of this process will be important for the development of drugs to treat acute myeloid leukemia and other cancers.Grant Funding Source: NIH

Molecular Insights into the Recognition of N-Terminal Histone Modifications by the BRPF1 Bromodomain

The monocytic leukemic zinc finger (MOZ) histone acetyltransferase (HAT) acetylates free histones H3, H4, H2A, and H2B in vitro and is associated with up-regulation of gene transcription. The MOZ HAT functions as a quaternary complex with the bromodomain-PHD finger protein 1 (BRPF1), inhibitor of growth 5 (ING5), and hEaf6 subunits. BRPF1 links the MOZ catalytic subunit to the ING5 and hEaf6 subunits, thereby promoting MOZ HAT activity. Human BRPF1 contains multiple effector domains with known roles in gene transcription, as well as chromatin binding and remodeling. However, the biological function of the BRPF1 bromodomain remains unknown. Our findings reveal novel interactions of the BRPF1 bromodomain with multiple acetyllysine residues on the N-terminus of histones and show that it preferentially selects for H2AK5ac, H4K12ac, and H3K14ac. We used chemical shift perturbation data from NMR titration experiments to map the BRPF1 bromodomain ligand binding pocket and identified key residues responsible for coordination of the post-translationally modified histones. Extensive molecular dynamics simulations were used to generate structural models of bromodomain–histone ligand complexes, to analyze hydrogen bonding and other interactions, and to calculate the binding free energies. Our results outline the molecular mechanism driving binding specificity of the BRPF1 bromodomain for discrete acetyllysine residues on the N-terminal histone tails. Together, these data provide insights into how histone recognition by the bromodomain directs the biological function of BRPF1, ultimately targeting the MOZ HAT complex to chromatin substrates.

Aberrant Expression miR-196a Is Associated With Abnormal Apoptosis, Invasion, and Proliferation of Pancreatic Cancer Cells

MiR-196a levels inversely correlated with survival in pancreatic adenocarcinoma patients. However, the functional contributions of miR-196a to pancreatic cancer remain unclear. Three lentiviral vectors encoding microRNA miR-196a precursor, inhibitor, and scrambled microRNA oligomer were transfected into Panc-1 cells, respectively. Then we explored the regulation of inhibitor of growth 5 (ING5) expression by miR-196a and its impact on apoptosis, invasion, and growth of pancreatic cancer cells. The lentiviral transfected Panc-1 cells were surgically implanted into the pancreas of mice. In vivo tumor growth and ING5 expression were measured. Down-regulation of ING5 expression was detected in cells transfected with miR-196a precursor (P < 0.01), accompanied by less apoptosis, increased invasion, and proliferation compared with control cells (P < 0.05). Cells transfected with miR-196a inhibitor revealed an opposite trend. Smaller detectable tumors were found in only 60% of mice after implantation of Lenti.miR-196a inhibitor-transfected Panc-1 cells compared with controls (360.7 ± 303.6 mm vs 511.58 ± 365.9 mm in controls; P < 0.01). Our results provide experimental evidence to support aberrant expression of miR-196a is associated with abnormal apoptosis, invasion, and proliferation of pancreatic cancer cells.

Molecular Basis of Histone Acetyllysine Recognition by the BRPF1 Bromodomain

The monocytic leukemic zinc‐finger (MOZ) histone acetyltransferase (HAT) was first identified as a fusion partner with the CREB binding protein (CBP) in a chromosomal translocation found in acute myeloid leukemia (AML). Disruption of MOZ HAT activity leads to leukemogenic transformations and oncogenesis. Bromodomain‐PHD finger protein 1 (BRPF1) is essential for MOZ HAT activity and links the MOZ catalytic subunit to the inhibitor of growth 5 (ING5) and hEaf6 subunits in the complex. BRPF1 also contains multiple epigenetic reader domains including a unique double plant homeodomain (PHD), a bromodomain (BRD) and a PWWP domain. These chromatin reader domains recognize post‐translationally modified histones and are often found in nuclear proteins that control fundamental cellular processes including gene transcription, DNA replication and recombination. Retention of these domains in leukemic fusion proteins is speculated to direct aberrant HAT activity and may be responsible for oncogenic transformations. However, the histone target(s) of the BRPF1 BRD are unknown, and its role in modulating the activity of the MOZ HAT complex is not well understood. A unique combination of peptide array, nuclear magnetic resonance, isothermal titration calorimetry and molecular docking experiments were used to identify the BRPF1 BRD ligands and characterize the molecular determinants driving histone recognition.

The clinicopathological significance of REIC expression in colorectal carcinomas.

REIC is down-regulated in immortalized cell lines compared with the parental normal counterparts, and could inhibit colony formation, tumor growth and induce apoptosis. Here, its expression was examined by immunohistochemistry on tissue microarray containing colorectal non-neoplastic mucosa (NNM), adenoma and adenocarcinoma. Colorectal carcinoma tissue and cell lines were studied for REIC expression or its secretory level by Western blot, RT-PCR or enzyme-linked immunosorbent assay (ELISA). The results demonstrated that REIC was differentially expressed in Colo201, Colo205, DLD-1, HCT-15, HCT-116, HT-29, KM-12, SW480, SW620, and WiDr with its secretion concentration less than 300 pg/mL. Carcinomas showed statistically lower REIC expression than matched NNM with no difference for protein content. Immunohistochemically, REIC expression was significantly decreased from NNM, adenoma to adenocarcinoma (p<0.05). REIC expression was negatively correlated with depth of invasion, TNM staging, dedifferentiation, Capase-3 and nuclear inhibitor of growth 5 (ING5) expression (p<0.05), while not with age, sex, tumor size, lymphatic or venous invasion, or lymph node metastasis (p>0.05). Kaplan-Meier analysis indicated that REIC expression was not associated with the prognosis of colorectal carcinomas (p>0.05). Cox's analysis demonstrated that lymphatic and venous invasion, lymph node metastasis, and UICC staging were independent prognostic factors for carcinoma (p<0.05). Our study indicated that down-regulated REIC expression might play an important role in colorectal adenoma-adenocarcinoma sequence and subsequent progression. Aberrant REIC expression might be employed as a good marker of pathogenesis and development of colorectal carcinomas.

Molecular Architecture of Quartet MOZ/MORF Histone Acetyltransferase Complexes

The monocytic leukemia zinc finger protein MOZ and the related factor MORF form tetrameric complexes with ING5 (inhibitor of growth 5), EAF6 (Esa1-associated factor 6 ortholog), and the bromodomain-PHD finger protein BRPF1, -2, or -3. To gain new insights into the structure, function, and regulation of these complexes, we reconstituted them and performed various molecular analyses. We found that BRPF proteins bridge the association of MOZ and MORF with ING5 and EAF6. An N-terminal region of BRPF1 interacts with the acetyltransferases; the enhancer of polycomb (EPc) homology domain in the middle part binds to ING5 and EAF6. The association of BRPF1 with EAF6 is weak, but ING5 increases the affinity. These three proteins form a trimeric core that is conserved from Drosophila melanogaster to humans, although authentic orthologs of MOZ and MORF are absent in invertebrates. Deletion mapping studies revealed that the acetyltransferase domain of MOZ/MORF is sufficient for BRPF1 interaction. At the functional level, complex formation with BRPF1 and ING5 drastically stimulates the activity of the acetyltransferase domain in acetylation of nucleosomal histone H3 and free histones H3 and H4. An unstructured 18-residue region at the C-terminal end of the catalytic domain is required for BRPF1 interaction and may function as an "activation lid." Furthermore, BRPF1 enhances the transcriptional potential of MOZ and a leukemic MOZ-TIF2 fusion protein. These findings thus indicate that BRPF proteins play a key role in assembling and activating MOZ/MORF acetyltransferase complexes.