The apoptosis-associated protein BNIPL interacts with two cell proliferation-related proteins, MIF and GFER

BNIPL is a promising biomarker of laryngeal cancer: novel insights from bioinformatics analysis and experimental validation

BACKGROUND

Laryngeal cancer (LC) is a malignant tumor with high incidence and mortality. We aim to explore key genes as novel biomarkers to find potential target of LC in clinic diagnosis and treatment.

METHODS

We retrieved GSE143224 and GSE84957 datasets from the Gene Expression Omnibus database to screen the differentially expressed genes (DEGs). Hub genes were identified from protein-protein interaction networks and further determined using receiver operating characteristic curves and principal component analysis. The expression of hub gene was verified by quantitative real time polymerase chain reaction. The transfection efficiency of BCL2 interacting protein like (BNIPL) was measured by western blot. Proliferation, migration, and invasion abilities were detected by Cell Counting Kit-8, wound-healing, and transwell assays, respectively.

RESULTS

Total 96 overlapping DEGs were screened out from GSE143224 and GSE84957 datasets. Six hub genes (BNIPL, KRT4, IGFBP3, MMP10, MMP3, and TGFBI) were identified from PPI network. BNIPL was selected as the target gene. The receiver operating characteristic curves of BNIPL suggested that the false positive rate was 18.5% and the true positive rate was 81.5%, showing high predictive values for LC. The expression level of BNIPL was downregulated in TU212 and TU686 cells. Additionally, overexpression of BNIPL suppressed the proliferation, migration, and invasion of TU212 and TU686 cells.

CONCLUSION

BNIPL is a novel gene signature involved in LC progression, which exerts an inhibitory effect on LC development. These findings provide a novel insight into the pathogenesis of LC.

Augmenter of liver regeneration: Essential for growth and beyond

Liver regeneration is a well-orchestrated process that is triggered by tissue loss due to trauma or surgical resection and by hepatocellular death induced by toxins or viral infections. Due to the central role of the liver for body homeostasis, intensive research was conducted to identify factors that might contribute to hepatic growth and regeneration. Using a model of partial hepatectomy several factors including cytokines and growth factors that regulate this process were discovered. Among them, a protein was identified to specifically support liver regeneration and therefore was named ALR (Augmenter of Liver Regeneration). ALR protein is encoded by GFER (growth factor erv1-like) gene and can be regulated by various stimuli. ALR is expressed in different tissues in three isoforms which are associated with multiple functions: The long forms of ALR were found in the inner-mitochondrial space (IMS) and the cytosol. Mitochondrial ALR (23 kDa) was shown to cooperate with Mia40 to insure adequate protein folding during import into IMS. On the other hand short form ALR, located mainly in the cytosol, was attributed with anti-apoptotic and anti-oxidative properties as well as its inflammation and metabolism modulating effects. Although a considerable amount of work has been devoted to summarizing the knowledge on ALR, an investigation of ALR expression in different organs (location, subcellular localization) as well as delineation between the isoforms and function of ALR is still missing. This review provides a comprehensive evaluation of ALR structure and expression of different ALR isoforms. Furthermore, we highlight the functional role of endogenously expressed and exogenously applied ALR, as well as an analysis of the clinical importance of ALR, with emphasis on liver disease and in vivo models, as well as the consequences of mutations in the GFER gene.

Macrophage migration inhibitory factor: A multifaceted cytokine implicated in multiple neurological diseases

Macrophage migration inhibitory factor (MIF) is a conserved cytokine found as a homotrimer protein. It is found in a wide spectrum of cell types in the body including neuronal and non-neuronal cells. MIF is implicated in several biological processes; chemo-attraction, cytokine activity, and receptor binding, among other functions. More recently, a chaperone-like activity has been added to its repertoire. In this review, we focus on the implication of MIF in the central nervous system and peripheries, its role in neurological disorders, and the mechanisms by which MIF is regulated. Numerous studies have associated MIF with various disease settings. MIF plays an important role in advocating tumorigenic processes, Alzheimer's disease, and is also upregulated in autism-spectrum disorders and spinal cord injury where it contributes to the severity of the injured area. The protective effect of MIF has been reported in amyotrophic lateral sclerosis by its reduction of aggregated misfolded SOD1, subsequently reducing the severity of this disease. Interestingly, a protective as well as pathological role for MIF has been implicated in stroke and cerebral ischemia, as well as depression. Thus, the role of MIF in neurological disorders appears to be diverse with both beneficial and adversary effects. Furthermore, its modulation is rather complex and it is regulated by different proteins, either on a molecular or protein level. This complexity might be dependent on the pathophysiological context and/or cellular microenvironment. Hence, further clarification of its diverse roles in neurological pathologies is warranted to provide new mechanistic insights which may lead in the future to the development of therapeutic strategies based on MIF, to fight some of these neurological disorders.

Macrophage migration inhibitory factor interacts with thioredoxin-interacting protein and induces NF-κB activity

The nuclear factor kappa B (NF-κB) pathway is pivotal in controlling survival and apoptosis of cancer cells. Macrophage migration inhibitory factor (MIF), a cytokine that regulates the immune response and tumorigenesis under inflammatory conditions, is upregulated in various tumors. However, the intracellular functions of MIF are unclear. In this study, we found that MIF directly interacted with thioredoxin-interacting protein (TXNIP), a tumor suppressor and known inhibitor of NF-κB activity, and MIF significantly induced NF-κB activation. MIF competed with TXNIP for NF-κB activation, and the intracellular MIF induced NF-κB target genes, including c-IAP2, Bcl-xL, ICAM-1, MMP2 and uPA, by inhibiting the interactions between TXNIP and HDACs or p65. Furthermore, we identified the interaction motifs between MIF and TXNIP via site-directed mutagenesis of their cysteine (Cys) residues. Cys⁵⁷ and Cys⁸¹ of MIF and Cys³⁶ and Cys¹²⁰ of TXNIP were responsible for the interaction. MIF reversed the TXNIP-induced suppression of cell proliferation and migration. Overall, we suggest that MIF induces NF-κB activity by counter acting the inhibitory effect of TXNIP on the NF-κB pathway via direct interaction with TXNIP. These findings reveal a novel intracellular function of MIF in the progression of cancer.

Macrophage migration inhibitory factor has a permissive role in concanavalin A-induced cell death of human hepatoma cells through autophagy

Concanavalin A (ConA) is a lectin and T-cell mitogen that can activate immune responses. In recent times, ConA-induced cell death of hepatoma cells through autophagy has been reported and its therapeutic effect was confirmed in a murine in situ hepatoma model. However, the molecular mechanism of ConA-induced autophagy is still unclear. As macrophage migration inhibitory factor (MIF), which is a proinflammatory cytokine, can trigger autophagy in human hepatoma cells, the possible involvement of MIF in ConA-induced autophagy was investigated in this study. We demonstrated that cell death is followed by an increment in MIF expression and secretion in the ConA-stimulated human hepatoma cell lines, HuH-7 and Hep G2. In addition, ConA-induced autophagy and cell death of hepatoma cells were blocked in the presence of an MIF inhibitor. Knockdown of endogenous MIF by small hairpin RNA confirmed that MIF is required for both ConA-induced autophagy and death of hepatoma cells. Furthermore, signal pathway studies demonstrated that ConA induces signal transducer and activator of transcription 3 (STAT3) phosphorylation to trigger MIF upregulation, which in turn promotes Bcl-2/adenovirus E1B 19 kDa-interacting protein 3 (BNIP3)-dependent autophagy. By using a murine in situ hepatoma model, we further demonstrated that MIF contributes to anti-hepatoma activity of ConA by regulating STAT3-MIF-BNIP3-dependent autophagy. In summary, our findings uncover a novel role of MIF in lectin-mediated anti-hepatoma activities by regulating autophagy.

Phylogeny and evolution of plant macrophage migration inhibitory factor/D-dopachrome tautomerase-like proteins

Background

The human (Homo sapiens) chemokine-like protein macrophage migration inhibitory factor (HsMIF) is a pivotal mediator of inflammatory, infectious and immune diseases including septic shock, colitis, malaria, rheumatoid arthritis, and atherosclerosis, as well as tumorigenesis. HsMIF has been found to exhibit several sequential and three-dimensional sequence motifs that in addition to its receptor binding sites include catalytic sites for oxidoreductase and tautomerase activity, which provide this 12.5 kDa protein with a remarkable functional complexity. A human MIF paralog, D-dopachrome tautomerase (HsDDT), has been identified, but its physiological relevance is incompletely understood. MIF/DDT-like proteins have been described in animals, protists and bacteria. Although based on sequence data banks the presence of MIF/DDT-like proteins has also been recognized in the model plant species Arabidopsis thaliana, details on these plant proteins have not been reported.

Results

To broaden the understanding of the biological role of these proteins across kingdoms we performed a comprehensive in silico analysis of plant MIF/DDT-like (MDL) genes/proteins. We found that the A. thaliana genome harbors three MDL genes, of which two are chiefly constitutively expressed in aerial plant organs, while the third gene shows stress-inducible transcript accumulation. The product of the latter gene likely localizes to peroxisomes. Structure prediction suggests that all three Arabidopsis proteins resemble the secondary and tertiary structure of human MIF. MIF-like proteins are found in all species across the plant kingdom, with an increasing family complexity towards evolutionarily advanced plant taxa. Plant MDL proteins are predicted to lack oxidoreductase activity, but possibly share tautomerase activity with human MIF/DDT.

Conclusions

Peroxisome localization seems to be a specific feature of a subset of MIF/DDT orthologs found in dicotyledonous plant species, which together with its stress-inducible gene expression might point to convergent evolution in higher plants and vertebrates towards neofunctionalization of MIF/MDL proteins in stress response pathways including innate immunity.

Electronic supplementary material

The online version of this article (doi:10.1186/s12862-015-0337-x) contains supplementary material, which is available to authorized users.

Airway gene expression in COPD is dynamic with inhaled corticosteroid treatment and reflects biological pathways associated with disease activity

Background

A core feature of chronic obstructive pulmonary disease (COPD) is the accelerated decline in forced expiratory volume in one second (FEV₁). The recent Groningen and Leiden Universities study of Corticosteroids in Obstructive Lung Disease (GLUCOLD) study suggested that particular phenotypes of COPD benefit from fluticasone±salmeterol by reducing the rate of FEV₁ decline, yet the underlying mechanisms are unknown.

Methods

Whole-genome gene expression profiling using the Affymetrix Gene ST array (V.1.0) was performed on 221 bronchial biopsies available from 89 COPD patients at baseline and after 6 and 30 months of fluticasone±salmeterol and placebo treatment in GLUCOLD.

Results

Linear mixed effects modelling revealed that the expression of 138 genes decreased, whereas the expression of 140 genes significantly upregulated after both 6 and 30 months of treatment with fluticasone±salmeterol versus placebo. A more pronounced treatment-induced change in the expression of 50 and 55 of these 278 genes was associated with a lower rate of decline in FEV₁ and Saint George Respiratory Questionnaire, respectively. Genes decreasing with treatment were involved in pathways related to cell cycle, oxidative phosphorylation, epithelial cell signalling, p53 signalling and T cell signalling. Genes increasing with treatment were involved in pathways related to focal adhesion, gap junction and extracellular matrix deposition. Finally, the fluticasone-induced gene expression changes were enriched among genes that change in the airway epithelium in smokers with versus without COPD in an independent data set.

Conclusions

The present study suggests that gene expression in biological pathways of COPD is dynamic with treatment and reflects disease activity. This study opens the gate to targeted and molecular phenotype-driven therapy of COPD.

Structure of the human sulfhydryl oxidase augmenter of liver regeneration and characterization of a human mutation causing an autosomal recessive myopathy

The sulfhydryl oxidase augmenter of liver regeneration (ALR) binds FAD in a helix-rich domain that presents a CxxC disulfide proximal to the isoalloxazine ring of the flavin. Head-to-tail interchain disulfide bonds link subunits within the homodimer of both the short, cytokine-like, form of ALR (sfALR), and a longer form (lfALR) which resides in the mitochondrial intermembrane space (IMS). lfALR has an 80-residue N-terminal extension with an additional CxxC motif required for the reoxidation of reduced Mia40 during oxidative protein folding within the IMS. Recently, Di Fonzo et al. [Di Fonzo, A., Ronchi, D., Lodi, T., Fassone, E., Tigano, M., Lamperti, C., Corti, S., Bordoni, A., Fortunato, F., Nizzardo, M., Napoli, L., Donadoni, C., Salani, S., Saladino, F., Moggio, M., Bresolin, N., Ferrero, I., and Comi, G. P. (2009) Am. J. Hum. Genet. 84, 594-604] described an R194H mutation of human ALR that led to cataract, progressive muscle hypotonia, and hearing loss in three children. The current work presents a structural and enzymological characterization of the human R194H mutant in lf- and sfALR. A crystal structure of human sfALR was determined by molecular replacement using the rat sfALR structure. R194 is located at the subunit interface of sfALR, close to the intersubunit disulfide bridges. The R194 guanidino moiety participates in three H-bonds: two main-chain carbonyl oxygen atoms (from R194 itself and from C95 of the intersubunit disulfide of the other protomer) and with the 2'-OH of the FAD ribose. The R194H mutation has minimal effect on the enzyme activity using model and physiological substrates of short and long ALR forms. However, the mutation adversely affects the stability of both ALR forms: e.g., by decreasing the melting temperature by about 10 degrees C, by increasing the rate of dissociation of FAD from the holoenzyme by about 45-fold, and by strongly enhancing the susceptibility of sfALR to partial proteolysis and to reduction of its intersubunit disulfide bridges by glutathione. Finally, a comparison of the TROSY-HSQC 2D NMR spectra of wild-type sfALR and its R194H mutant reveals a significant increase in conformational flexibility in the mutant protein. In sum, these in vitro data document the major impact of the seemingly conservative R194H mutation on the stability of dimeric ALR and complement the in vivo observations of Di Fonzo et al.

The fission yeast inhibitor of growth (ING) protein Png1p functions in response to DNA damage

In budding yeast and human cells, ING (inhibitor of growth) tumor suppressor proteins play important roles in response to DNA damage by modulating chromatin structure through collaborating with histone acetyltransferase or histone deacetylase complexes. However, the biological functions of ING family proteins in fission yeast are poorly defined. Here, we report that Png1p, a fission yeast ING homolog protein, is required for cell growth under normal and DNA-damaged conditions. Png1p was further confirmed to regulate histone H4 acetylation through collaboration with the MYST family histone acetyltransferase 1 (Mst1). Additionally, both fission yeast PNG1 and MST1 can functionally complement their budding yeast correspondence homologs YNG2 and ESA1, respectively. These results suggest that ING proteins in fission yeast might also conserve function, similar to ING proteins in budding yeast and human cells. We also showed that decreased acetylation in Deltapng1 cells resulted in genome-wide down-regulation of 756 open reading frames, including the central DNA repair gene RAD22. Overexpression of RAD22 partially rescued the png1 mutant phenotype under both normal and DNA-damaged conditions. Furthermore, decreased expression of RAD22 in Deltapng1 cells was confirmed to be caused by decreased H4 acetylation at its promoter. Altogether, these results indicate that Png1p is required for histone H4 acetylation and functions upstream of RAD22 in the DNA damage response pathway.

Transcriptome analysis of mammary epithelial subpopulations identifies novel determinants of lineage commitment and cell fate

Background

Understanding the molecular control of cell lineages and fate determination in complex tissues is key to not only understanding the developmental biology and cellular homeostasis of such tissues but also for our understanding and interpretation of the molecular pathology of diseases such as cancer. The prerequisite for such an understanding is detailed knowledge of the cell types that make up such tissues, including their comprehensive molecular characterisation. In the mammary epithelium, the bulk of the tissue is composed of three cell lineages, namely the basal/myoepithelial, luminal epithelial estrogen receptor positive and luminal epithelial estrogen receptor negative cells. However, a detailed molecular characterisation of the transcriptomic differences between these three populations has not been carried out.

Results

A whole transcriptome analysis of basal/myoepithelial cells, luminal estrogen receptor negative cells and luminal estrogen receptor positive cells isolated from the virgin mouse mammary epithelium identified 861, 326 and 488 genes as highly differentially expressed in the three cell types, respectively. Network analysis of the transcriptomic data identified a subpopulation of luminal estrogen receptor negative cells with a novel potential role as non-professional immune cells. Analysis of the data for potential paracrine interacting factors showed that the basal/myoepithelial cells, remarkably, expressed over twice as many ligands and cell surface receptors as the other two populations combined. A number of transcriptional regulators were also identified that were differentially expressed between the cell lineages. One of these, Sox6, was specifically expressed in luminal estrogen receptor negative cells and functional assays confirmed that it maintained mammary epithelial cells in a differentiated luminal cell lineage.

Conclusion

The mouse mammary epithelium is composed of three main cell types with distinct gene expression patterns. These suggest the existence of a novel functional cell type within the gland, that the basal/myoepithelial cells are key regulators of paracrine signalling and that there is a complex network of differentially expressed transcription factors controlling mammary epithelial cell fate. These data will form the basis for understanding not only cell fate determination and cellular homeostasis in the normal mammary epithelium but also the contribution of different mammary epithelial cell types to the etiology and molecular pathology of breast disease.

Direct interaction between NM23-H1 and macrophage migration inhibitory factor (MIF) is critical for alleviation of MIF-mediated suppression of p53 activity

Macrophage migration inhibitory factor (MIF) is a pluripotent cytokine that is involved in host immune and inflammatory responses, as well as tumorigenesis. However, the regulatory mechanism of MIF function is unclear. Here we report that the NM23-H1 interacts with MIF in cells, as demonstrated by cotransfection and coimmunoprecipitation experiments. Analysis of cysteine (Cys) to serine (Ser) substitution mutants of NM23-H1 (C4S, C109S, and C145S) and MIF (C57S, C60S, and C81S) revealed that Cys(145) of NM23-H1 and Cys(60) of MIF are responsible for complex formation. NM23-H1-MIF complexes were dependent on reducing conditions, such as the presence of dithiothreitol or beta-mercaptoethanol, but not H(2)O(2). NM23-H1 alleviated the MIF-mediated suppression of p53-induced apoptosis and cell cycle arrest by promoting the dissociation of MIF from MIF-p53 complexes. In addition, NM23-H1 significantly inhibited the MIF-induced proliferation of quiescent NIH 3T3 cells through a direct interaction with MIF, and decreased the MIF-induced activation of phosphatidylinositol 3-kinase/PDK1 and p44/p42 extracellular signal-regulated (ERK) mitogen-activated protein kinase. The results of the current study suggest that the NM23-H1 functions as a negative regulator of MIF.

Identification of interaction between hepatopoietin 205 and cytochrome C

AIM: To identify the interaction between hepatopoietin 205 (HPO205) and cytochrome C (Cytc).

METHODS: The coding genes of HPO205 and Cytc, amplified by polymerase chain reaction, were cloned into pDBLeu and pPC86 vector respectively. The interaction was confirmed by co-transformation with the recombinant plasmids into MaV203 of yeast two-hybrid system (Y2H), and verified by GST-Pull down assay simultaneously.

RESULTS: The coding genes of HPO205 and Cytc were successfully cloned into relevant vectors, and the obtained vectors were named as pDBLeu-GRER, pDBLeu-CYCS, pPC86-GFER and pPC86-CYCS. After Y2H identification, we found that co-transformation of pDBLeu-GFER pPC86-CYCS activated reporter genes Ura and His, but co-transformation of pDBLeu-CYCS and pPC86-GFER activated no reporter genes. GST-Pull down assay showed that HPO205 was deposited by GST-CYCS, but not by GST, verifying the interaction between HPO205 and Cytc.

CONCLUSION: The interaction between HPO205 and Cytc suggests that HPO205 participates in the biology processes of electron transfer or (and) apoptosis via Cytc.

Mitochondrial protein targets of thiol-reactive electrophiles

Mitochondria serve a pivotal role in the regulation of apoptosis or programmed cell death. Recent studies have demonstrated that reactive electrophiles induce mitochondrion-dependent apoptosis. We hypothesize that covalent modification of specific mitochondrial proteins by reactive electrophiles serves as a trigger leading to the initiation of apoptosis. In this study, we identified protein targets of the model biotin-tagged electrophile probes N-iodoacetyl- N-biotinylhexylene-diamine (IAB) and 1-biotinamido-4-(4'-[maleimidoethylcyclohexane]carboxamido)butane (BMCC) in HEK293 cell mitochondrial fractions by liquid chromatography-tandem mass spectrometry (LC-MS-MS). These electrophiles reproducibly adducted a total of 1693 cysteine residues that mapped to 809 proteins. Protein modifications were selective in that only 438 cysteine sites in 1255 cysteinyl peptide adducts (35%) and 362 of the 809 identified protein targets (45%) were adducted by both electrophiles. Of these, approximately one-third were annotated to the mitochondria following protein database analysis. IAB initiated apoptotic events including cytochrome c release, caspase-3 activation, and poly(ADP-ribose)polymerase (PARP) cleavage, whereas BMCC did not. Of the identified targets of IAB and BMCC, 44 were apoptosis-related proteins, and adduction site specificity on these targets differed between the two probes. Differences in sites of modification between these two electrophiles may reveal alkylation sites whose modification triggers apoptosis.

Acetyl-Coenzyme A acyltransferase 2 attenuates the apoptotic effects of BNIP3 in two human cell lines

BNIP3 is a unique pro-apoptotic protein which belongs to the BH3-only subset of the Bcl-2 family and localizes on mitochondrial membrane. Despite the inherent difficulty of identifying binding partners for membrane proteins, several binding partners for BNIP3 have been identified. In this study, a modified split-ubiquitin membrane yeast two-hybrid system was constructed and used to identify acetyl-Coenzyme A acyltransferase 2 (ACAA2) as a new BNIP3 binding partner. The interaction between BNIP3 and ACAA2 was confirmed by pull-down and co-immunoprecipitation assays. ACAA2 was also found to co-localize with BNIP3 in mitochondria. Furthermore, the apoptosis induced by over-expressed BNIP3 via transfection or hypoxia treatment was abolished by ACAA2 in human hepatocellular carcinoma HepG2 cells and osteosarcoma U-2 OS cells. These results strongly suggest that ACAA2 be a functional BNIP3 binding partner and provide a possible linkage between fatty acid metabolism and apoptosis of cells.

Macrophage migration inhibitory factor governs endothelial cell sensitivity to LPS-induced apoptosis

Human endothelial cells (EC) are typically resistant to the apoptotic effects of stimuli associated with lung disease. The determinants of this resistance remain incompletely understood. Macrophage migration inhibitory factor (MIF) is a proinflammatory cytokine produced by human pulmonary artery EC (HPAEC). Its expression increases in response to various death-inducing stimuli, including lipopolysaccharide (LPS). We show here that silencing MIF expression by RNA interference (MIF siRNA) dramatically reduces MIF mRNA expression and the LPS-induced increase in MIF protein levels, thereby sensitizing HPAECs to LPS-induced cell death. Addition of recombinant human MIF (rhMIF) protein prevents the death-sensitizing effect of MIF siRNA. A common mediator of apoptosis resistance in ECs is the death effector domain (DED)-containing protein, FLIP (FLICE-like inhibitory protein). We show that LPS induces a transcription-independent increase in the short isoform of FLIP (FLIP(s)). This increase is blocked by MIF siRNA but restored with the addition of recombinant MIF protein (rHMIF). While FLIP(s) siRNA also sensitizes HPAECs to LPS-induced death, the addition of rhMIF does not affect this sensitization, placing MIF upstream of FLIP(s) in preventing HPAEC death. These studies demonstrate that MIF is an endogenous pro-survival factor in HPAECs and identify a novel mechanism for its role in apoptosis resistance through the regulation of FLIP(s). These results show that MIF can protect vascular endothelial cells from inflammation-associated cell damage.

The orphan nuclear receptor Rev-erbbeta recruits Tip60 and HDAC1 to regulate apolipoprotein CIII promoter

Nuclear hormone receptors function as ligand activated transcription factors. Ligand binding and modification such as acetylation have been reported to regulate nuclear hormone receptors. The orphan receptors, Rev-erbalpha and Rev-erbbeta, are members of the nuclear receptor superfamily and act as transcriptional repressors. In this study, the role of recruitment of co-factors by Rev-erbbeta and acetylation of Rev-erbbeta in modulating apolipoprotein CIII (apoCIII) transcription were investigated. Rev-erbbeta was found to transcriptionally repress apoCIII after binding to the apoCIII promoter. Tip60, a histone acetyl-transferase (HAT), was a novel binding partner for Rev-erbbeta and recruited to the apoCIII promoter by Rev-erbbeta. Tip60 was able to acetylate Rev-erbbeta and relieve the apoCIII repression mediated by Rev-erbbeta. This de-repression effect depended on acetylation of Rev-erbbeta at its RXKK motif by Tip60. In addition, histone deacetylase 1 (HDAC1) interacted with Rev-erbbeta and was recruited to the apoCIII promoter by Rev-erbbeta to antagonize Tip60's activity. Taken together, we have provided evidence that Rev-erbbeta modulates the apoCIII gene expression by recruiting different transcription co-activator or co-repressor.

A zinc finger HIT domain-containing protein, ZNHIT-1, interacts with orphan nuclear hormone receptor Rev-erbbeta and removes Rev-erbbeta-induced inhibition of apoCIII transcription

The orphan receptors, Rev-erbalpha and Rev-erbbeta, are members of the nuclear receptor superfamily and specifically repress apolipoprotein CIII (apoCIII) gene expression in rats and humans. Moreover, Rev-erbalpha null mutant mice have elevated very low density lipoprotein triacylglycerol and apoCIII levels. However, ligands for Rev-erb are unknown and the regulatory mechanism of Rev-erb is poorly understood. Conceivably, cofactors for Rev-erb may play an important role in the regulation of lipid metabolism. In this study, a zinc finger HIT domain-containing protein, ZNHIT-1, interacted with Rev-erbbeta. ZNHIT-1 was found to be a conserved protein in eukaryotes and was highly abundant in human liver. Furthermore, ZNHIT-1 was identified as a nuclear protein. Serial truncated fragments and substitution mutations established a putative nuclear localization signal at amino acids 38-47 of ZNHIT-1. A putative ligand-binding domain of Rev-erbbeta and the FxxLL motif of ZNHIT-1 were required for their interaction. Finally, ZNHIT-1 was recruited by Rev-erbbeta to the apoCIII promoter and removed the Rev-erbbeta-induced inhibition of apoCIII transcription. These findings demonstrate that ZNHIT-1 functions as a cofactor to regulate the activity of Rev-erbbeta, and may play a role in lipid metabolism.

Characterization of human dopamine responsive protein DRG-1 that binds to p75NTR-associated cell death executor NADE

Expression of human dopamine responsive gene-1 (DRG-1) is up-regulated in response to treatment of dopamine in the rat astrocytes. However, its functions are not clear up to now. In the presented studies, DRG-1 was identified to be a conserved gene in the vertebrate and expressed abundantly in human testis, brain and skeletal muscle. DRG-1 was shown to interact with human p75NTR-associated cell death executor (NADE) in vivo and in vitro, and the interaction occurred in cytoplasm. The regions required for the interaction were subsequently mapped to the N-terminal of DRG-1 and the C-terminal of NADE. Furthermore, MTT assay showed that stable expression of DRG-1 in 293 cells could promote cell proliferation, and this promotion was suppressed by overexpression of NADE. In flow cytometry cell cycle analysis, overexpression of DRG-1 in 293 or PC12 cells increased the population of cells in the S phase with a concomitant decrease in G0/G1 population. These findings suggest that DRG-1 may contribute to the dopamine-induced cell growth, which is negatively regulated by NADE.

BCL2 family of apoptosis-related genes: functions and clinical implications in cancer

One of the most effective ways to combat different types of cancer is through early diagnosis and administration of effective treatment, followed by efficient monitoring that will allow physicians to detect relapsing disease and treat it at the earliest possible time. Apoptosis, a normal physiological form of cell death, is critically involved in the regulation of cellular homeostasis. Dysregulation of programmed cell death mechanisms plays an important role in the pathogenesis and progression of cancer as well as in the responses of tumours to therapeutic interventions. Many members of the BCL2 (B-cell CLL/lymphoma 2; Bcl-2) family of apoptosis-related genes have been found to be differentially expressed in various malignancies, and some are useful prognostic cancer biomarkers. We have recently cloned a new member of this family, BCL2L12, which was found to be differentially expressed in many tumours. Most of the BCL2 family genes have been found to play a central regulatory role in apoptosis induction. Results have made it clear that a number of coordinating alterations in the BCL2 family of genes must occur to inhibit apoptosis and provoke carcinogenesis in a wide variety of cancers. However, more research is required to increase our understanding of the extent to which and the mechanisms by which they are involved in cancer development, providing the basis for earlier and more accurate cancer diagnosis, prognosis and therapeutic intervention that targets the apoptosis pathways. In the present review, we describe current knowledge of the function and molecular characteristics of a series of classic but also newly discovered genes of the BCL2 family as well as their implications in cancer development, prognosis and treatment.

Expression profiling reveals meiotic male germ cell mRNAs that are translationally up- and down-regulated

Gametes rely heavily on posttranscriptional control mechanisms to regulate their differentiation. In eggs, maternal mRNAs are stored and selectively activated during development. In the male, transcription ceases during spermiogenesis, necessitating the posttranscriptional regulation of many paternal mRNAs required for spermatozoan assembly and function. To date, most of the testicular mRNAs known to be translationally regulated are initially transcribed in postmeiotic cells. Because protein synthesis occurs on polysomes and translationally inactive mRNAs are sequestered as ribonucleoproteins (RNPs), movement of mRNAs between these fractions is indicative of translational up- and down-regulation. Here, we use microarrays to analyze mRNAs in RNPs and polysomes from testis extracts of prepuberal and adult mice to characterize the translation state of individual mRNAs as spermatogenesis proceeds. Consistent with published reports, many of the translationally delayed postmeiotic mRNAs shift from the RNPs into the polysomes, establishing the validity of this approach. In addition, we detect another 742 mouse testicular transcripts that show dramatic shifts between RNPs and polysomes. One subgroup of 35 genes containing the known, translationally delayed phosphoglycerate kinase 2 (Pgk2) is initially transcribed during meiosis and is translated in later-stage cells. Another subgroup of 82 meiotically expressed genes is translationally down-regulated late in spermatogenesis. This high-throughput approach defines the changing translation patterns of populations of genes as male germ cells differentiate and identifies groups of meiotic transcripts that are translationally up- and down-regulated.

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Macrophage migration inhibitory factor directly interacts with hepatopoietin and regulates the proliferation of hepatoma cell

Macrophage migration inhibitory factor (MIF) is a pluripotent cytokine involved in inflammation and immune responses as well as in growth factor-dependent cell proliferation, cell cycle, angiogenesis, and tumorigenesis. Several studies have documented MIF expression in the sera following hepatic resection or in the course of liver cancer progression, but there is a paucity of information regarding the effect of MIF on hepatoma cells and relating mechanisms. In this paper, by [3H] thymidine incorporation, we found that exogenously added MIF could promote the proliferation of HepG2 in a dose-dependent manner. Hepatopoietin (HPO), as a liver-specific regeneration augmenter, could be induced by the expression of MIF in hepatoma cells. The activity of HPO promoter was increased, and its levels were enhanced after MIF was overexpressed in hepatoma cells. The similarities between HPO and MIF in structure and action led us to investigate their interaction and the inducing biological significance. Using yeast two-hybrid identification, we found that HPO interacted with MIF in yeast cells, and their binding ability was higher than that between HPO and JAB1 (Jun activation domain binding protein) or MIF and JAB1 in yeast cells. Their interaction was further verified by His pull-down assay in vitro and coimmunoprecipitation experiment in vivo. They were colocalized in the cytoplasm. Both HPO and MIF could bind to JAB1 and modulate the AP-1 pathway. When HPO and MIF were cotransfected into HepG2 cells, the binding activity of MIF to JAB1 was reduced, and the activity of AP-1 was improved. In contrast, MIF overexpressed in HepG2 was unable to interfere with the binding activity of HPO to JAB1, but its potentiation on AP-1 activity was reduced significantly. Taken together, these results indicate that MIF plays an important role in the proliferation of hepatoma cells, and the effect of MIF is in concert with HPO.

Large-scale cDNA transfection screening for genes related to cancer development and progression

A large-scale assay was performed by transfecting 29,910 individual cDNA clones derived from human placenta, fetus, and normal liver tissues into human hepatoma cells and 22,926 cDNA clones into mouse NIH 3T3 cells. Based on the results of colony formation in hepatoma cells and foci formation in NIH 3T3 cells, 3,806 cDNA species (8,237 clones) were found to possess the ability of either stimulating or inhibiting cell growth. Among them, 2,836 (6,958 clones) were known genes, 372 (384 clones) were previously unrecognized genes, and 598 (895 clones) were unigenes of uncharacterized structure and function. A comprehensive analysis of the genes and the potential mechanisms for their involvement in the regulation of cell growth is provided. The genes were classified into four categories: I, genes related to the basic cellular mechanism for growth and survival; II, genes related to the cellular microenvironment; III, genes related to host-cell systemic regulation; and IV, genes of miscellaneous function. The extensive growth-regulatory activity of genes with such highly diversified functions suggests that cancer may be related to multiple levels of cellular and systemic controls. The present assay provides a direct genomewide functional screening method. It offers a better understanding of the basic machinery of oncogenesis, including previously undescribed systemic regulatory mechanisms, and also provides a tool for gene discovery with potential clinical applications.

BNIPL-2, a novel homologue of BNIP-2, interacts with Bcl-2 and Cdc42GAP in apoptosis

The execution phase of apoptosis is characterized by marked changes in cell morphology that include contraction and membrane blebbing. Little is known about the mechanisms underlying this process. We report here the identification of a novel member of BNIPL family, designated Bcl-2/adenovirus E1B 19kDa interacting protein 2 like-2 (BNIPL-2), which interacts with Bcl-2 and Cdc42GAP. We found that the human BNIPL-2 shares homology to human BNIP-2 and also possesses a BNIP-2 and Cdc42GAP homology (BCH) domain. Deletion experiments indicated that the BCH domain of BNIPL-2 is critical for its interactions with the Bcl-2 and Cdc42GAP and also for its cell death-inducing function. Our data showed that BNIPL-2 may be a linker protein located at the front end of Bcl-2 pathway for DNA fragmentation and Cdc42 signaling for morphological changes during apoptosis. We propose that BNIPL-2 protein may play an important role in regulation of both pathways for DNA fragmentation and for formation of membrane blebs in apoptotic cells.