SFA-2, a novel bZIP transcription factor induced by human T-cell leukemia virus type I, is highly expressed in mature lymphocytes

An activating mutation of interferon regulatory factor 4 (IRF4) in adult T-cell leukemia

The human T-cell leukemia virus-1 (HTLV-1) oncoprotein Tax drives cell proliferation and resistance to apoptosis early in the pathogenesis of adult T-cell leukemia (ATL). Subsequently, probably as a result of specific immunoediting, Tax expression is down-regulated and functionally replaced by somatic driver mutations of the host genome. Both amplification and point mutations of interferon regulatory factor 4 (IRF4) have been previously detected in ATL., K59R is the most common single-nucleotide variation of IRF4 and is found exclusively in ATL. High-throughput whole-exome sequencing revealed recurrent activating genetic alterations in the T-cell receptor, CD28, and NF-κB pathways. We found that IRF4, which is transcriptionally activated downstream of these pathways, is frequently mutated in ATL. IRF4 RNA, protein, and IRF4 transcriptional targets are uniformly elevated in HTLV-1-transformed cells and ATL cell lines, and IRF4 was bound to genomic regulatory DNA of many of these transcriptional targets in HTLV-1-transformed cell lines. We further noted that the K59R IRF4 mutant is expressed at higher levels in the nucleus than WT IRF4 and is transcriptionally more active. Expression of both WT and the K59R mutant of IRF4 from a constitutive promoter in retrovirally transduced murine bone marrow cells increased the abundance of T lymphocytes but not myeloid cells or B lymphocytes in mice. IRF4 may represent a therapeutic target in ATL because ATL cells select for a mutant of IRF4 with higher nuclear expression and transcriptional activity, and overexpression of IRF4 induces the expansion of T lymphocytes in vivo.

Increased BATF expression is associated with the severity of liver damage in patients with chronic hepatitis B

T helper (Th) 17 cells have a critical role in the pathogenesis of chronic hepatitis B virus (HBV) infection, and basic leucine zipper transcription factor, ATF-like (BATF) is a newly identified transcriptional factor regulating the differentiation of Th17 cells. However, its precise role in patients with chronic hepatitis B remains unclear. Sixty chronic hepatitis B (CHB) patients, twenty-two acute-on-chronic hepatitis B liver failure (ACHBLF) patients and seventeen healthy controls were included in our study. Both peripheral and intrahepatic expressions of BATF were analyzed by flow cytometry, quantitative real-time polymerase chain reaction and immunohistochemical staining. Peripheral BATF mRNA and protein expression levels were higher in CHB patients than those in healthy controls. Particularly in ACHBLF patients, the BATF mRNA and protein levels were further increased over those in CHB patients. Intrahepatic BATF-positive infiltrating cells were enriched in portal area of CHB patients, and more positive cells were found in patients with higher inflammation grade. Peripheral BATF expression was positively correlated with serum parameters of liver injury and plasma HBV DNA load. Furthermore, a positive correlation was found between the frequency of BATF-positive CD3⁺ T cells and the increased Th17 response in chronic HBV-infected patients. BATF over-expression might augment Th17 cell response and relate to the disease progression of CHB.

Targeting Batf2 for infectious diseases and cancer. Oncotarget. 2015;6:26575-26582. [PMID: 26376615 PMCID: PMC4694937 DOI: 10.18632/oncotarget.5576]

The family members Batf, Batf2 and Batf3 belong to a class of transcription factors containing basic leucine zipper domains that regulate various immunological functions and control the development and differentiation of immune cells. Functional studies by others demonstrated a predominant role for Batf in controlling Th2 cell functions and lineage development of T lymphocytes as well as a critical role of Batf, Batf2 and Batf3 in CD8α+dendritic cell development. Moreover, Batf family member expression was measured in a vast collection of mouse and human cell types by cap analysis gene expression (CAGE), a recent developed sequencing technology, showing reasonable expression spectrum in immune cells consistent with previously published expression profiles. Batf and Batf3 were highly expressed in lymphocytes and the earlier moderately expressed in myeloid lineages. Batf2 was predominantly expressed in monocytes/macrophages. Functional studies in mice demonstrated that Batf2 has a central role in macrophage activation by regulating inflammatory responses during lipopolysaccharides stimulation and mycobacterial infection. Hence, Batf2 could be used as a biomarker and a potential host directed drug target in tuberculosis. Moreover, Batf2 act as a tumor suppressor gene and augmenting Batf2 in malignant cells might be an encouraging therapeutic treatment against cancer.

The transcription factor BATF modulates cytokine-mediated responses in T cells

The transcription factor BATF (basic leucine zipper transcription factor, ATF-like), belongs to the AP-1 family of transcription factors and has been shown to be predominantly expressed in cells of haematopoietic origin, especially in B and T cells. In studies using Batf-deficient mice, a profound defect in the differentiation of T helper cells type 17 (Th17) and follicular T helper cells (Tfh) was described, as well as an impairment of antibody production with switched isotypes. More recently BATF has been described to influence also Th2 and Th9 responses in models of murine experimental asthma. In CD8(+) T cells BATF has been found associated with anti-viral responses. This review summarizes the role of BATF in CD4(+) T cell subsets and in CD8(+) T cells, with particular focus on this transcription factor in the setting of allergic asthma.

Basic leucine zipper transcription factor, ATF-like (BATF) regulates epigenetically and energetically effector CD8 T-cell differentiation via Sirt1 expression

CD8 T cells play a critical role in protection against viral infections. During effector differentiation, CD8 T cells dramatically change chromatin structure and cellular metabolism, but how energy production increases in response to these epigenetic changes is unknown. We found that loss of basic leucine zipper transcription factor, ATF-like (BATF) inhibited effector CD8 T-cell differentiation. At the late effector stage, BATF was induced by IL-12 and required for IL-12-mediated histone acetylation and survival of effector T cells. BATF, together with c-Jun, transcriptionally inhibited expression of the nicotinamide adenine dinucleotide (NAD(+))-dependent deacetylase Sirt1, resulting in increased histone acetylation of the T-bet locus and increased cellular NAD(+), which increased ATP production. In turn, high levels of T-bet expression and ATP production promoted effector differentiation and cell survival. These results suggest that BATF promotes effector CD8 T-cell differentiation by regulating both epigenetic remodeling and energy metabolism through Sirt1 expression.

Nucleolin binds specifically to an AP-1 DNA sequence and represses AP1-dependent transactivation of the matrix metalloproteinase-13 gene

Transcriptional regulation via activator protein-1 (AP-1) protein binding to AP-1 binding sites within gene promoter regions of AP-1 target genes plays a key role in controlling cellular invasion, proliferation, and oncogenesis, and is important to pathogenesis of arthritis and cardiovascular disease. To identify new proteins that interact with the AP-1 DNA binding site, we performed the DNA affinity chromatography-based Nucleotide Affinity Preincubation Specificity TEst of Recognition (NAPSTER) assay, and discovered a 97 kDa protein that binds in vitro to a minimal AP-1 DNA sequence element. Mass spectrometric fragmentation sequencing determined that p97 is nucleolin. Immunoblotting of DNA affinity-purified material with anti-nucleolin antibodies confirmed this identification. Nucleolin also binds the AP-1 site in gel shift assays. Nucleolin interacts in NAPSTER with the AP-1 site within the promoter sequence of the metalloproteinase-13 gene (MMP-13), and binds in vivo in chromatin immunoprecipitation assays in the vicinity of the AP-1 site in the MMP-13 promoter. Overexpression of nucleolin in human HeLa cervical carcinoma cells significantly represses AP-1 dependent gene transactivation of a minimal AP-1 reporter construct and of an MMP-13 promoter reporter sequence. This is the first report of nucleolin binding and transregulation at the AP-1 site.

YB-1 binds to the MMP-13 promoter sequence and represses MMP-13 transactivation via the AP-1 site

Matrix metalloproteinases (MMPs) are key enzymes that implement degradation of the extracellular matrix during cellular invasion in development, tissue remodeling, and pathogenic disease states. MMP-13 has pivotal roles in the pathogenesis of invasive cancers and arthritis. Here we report the identification of Y-box binding protein-1 (YB-1) as a new repressor of MMP-13 transactivation. YB-1 binds in vitro in DNA affinity chromatography to the activator protein-1 (AP-1) DNA sequence within the MMP-13 promoter. Chromatin immunoprecipitation assays reveal that YB-1 binds in living cells to the MMP-13 gene promoter to a region of the MMP-13 promoter containing the AP-1 site. YB-1 represses tumor promoter-induced MMP-13 promoter transactivation at the AP-1 site. This is the first report demonstrating YB-1 binding in vitro and in living cells to a mammalian AP-1 target gene, and the first report of YB-1 regulation of the MMP-13 promoter.

YB-1 represses AP1-dependent gene transactivation and interacts with an AP-1 DNA sequence

Involvement of the AP-1 (activator protein-1) transcription factor has been demonstrated previously in the regulation of cell proliferation and cell-cycle progression, in the control of cell migration, invasion and metastasis, and in signal transduction, stress responsiveness, DNA replication and DNA repair. YB-1 (Y-box-binding protein-1) has also been implicated in many of these processes. However, the mechanism by which YB-1 mediates these processes is poorly understood. In the present study, we report that overexpression of a transfected gene encoding YB-1 in human HeLa cervical carcinoma cells significantly represses the transactivation of a minimal AP-1 reporter construct in response to the tumour promoter PMA. YB-1 also represses mRNA expression and PMA-induced promoter transactivation of the endogenous AP-1 target gene encoding matrix metalloproteinase-12 (metalloelastase). YB-1 transrepression of both the minimal and matrix metalloproteinase-12 promoter reporter constructs is dependent on the AP-1 sequence. To identify new nuclear proteins that bind specifically to the AP-1 DNA-binding site, we devised a DNA-affinity-chromatography-based assay termed NAPSTER (nucleotide-affinity preincubation specificity test of recognition) and discovered a 49 kDa protein from human cancer cells that binds in a sequence-specific manner to the AP-1 DNA sequence. By tandem MS fragmentation sequencing analyses we determined that p49 is a YB-1. Immunoblotting of the NAPSTER-purified p49 protein using anti-YB-1 antibodies confirmed YB-1 binding to the AP-1 DNA sequence, as did gel mobility-supershift assays using YB-1 antibodies. This is the first report of YB-1 transrepression and interaction at the AP-1 DNA-binding site.

Tumor model-specific proviral insertional mutagenesis of the Fos/Jdp2/Batf locus

Retroviral activation of the AP-1/ATF super family member Jdp2 was recently reported to be a common event in M-MLV-induced T cell lymphoma in p27-null C57x129 mice as compared to wild type-inoculated mice but has not been found important in other models. On the basis of retroviral tag retrieval from 1190 individual Akv- and SL3-3-induced lymphomas, we here report that insertional mutagenesis into the 250-kb Fos/Jdp2/Batf locus is associated with SL3-3 MLV-induced T but not Akv-induced B cell lymphomas of NMRI and SWR mice. Integration pattern and clonality analyses suggest that Jdp2 participates in SL3-3-induced tumorigenesis distinctly as compared to the M-MLV setting. Northern blot analysis showed Jdp2 to be alternatively spliced in various normal tissues as well as MLV-induced lymphomas. Interestingly, in some tumors, proviral insertion seems to activate different mRNA sub-species. Whereas elevated mRNA levels of the Fos gene could not be correlated with provirus presence, in one case, Northern blot analysis as well as quantitative real-time PCR indicated proviral activation of the AP-1 super family member Batf, a gene not previously reported to be a target of insertional mutagenesis. A novel integration cluster between Jdp2 and Batf apparently did not influence the expression level of either gene, underscoring the importance of addressing expression effects to identify target genes of insertion. Altogether, such distinct insertion patterns point to different mechanism of activation of specific proto-oncogenes and are consequently of importance for the understanding of proviral activation mechanisms as well as the specific role of individual oncogenes in tumor development.

Phosphorylation of BATF regulates DNA binding: a novel mechanism for AP-1 (activator protein-1) regulation

BATF is a member of the AP-1 (activator protein-1) family of bZIP (basic leucine zipper) transcription factors that form transcriptionally inhibitory, DNA binding heterodimers with Jun proteins. In the present study, we demonstrate that BATF is phosphorylated in vivo on multiple serine and threonine residues and at least one tyrosine residue. Reverse-polarity PAGE revealed that serine-43 and threonine-48 within the DNA binding domain of BATF are phosphorylated. To model phosphorylation of the BATF DNA binding domain, serine-43 was replaced by an aspartate residue. BATF(S43D) retains the ability to dimerize with Jun proteins in vitro and in vivo, and the BATF(S43D):Jun heterodimer localizes properly to the nucleus of cells. Interestingly, BATF(S43D) functions like wild-type BATF to reduce AP-1-mediated gene transcription, despite the observed inability of the BATF(S43D):Jun heterodimer to bind DNA. These data demonstrate that phosphorylation of serine-43 converts BATF from a DNA binding into a non-DNA binding inhibitor of AP-1 activity. Given that 40% of mammalian bZIP transcription factors contain a residue analogous to serine-43 of BATF in their DNA binding domains, the phosphorylation event described here represents a mechanism that is potentially applicable to the regulation of many bZIP proteins.

EBNA2 and activated Notch induce expression of BATF

The immortalization of human B lymphocytes by Epstein-Barr virus (EBV) requires the virus-encoded transactivator EBNA2 and the products of both viral and cellular genes which serve as EBNA2 targets. In this study, we identified BATF as a cellular gene that is up-regulated dramatically within 24 h following the infection of established and primary human B cells with EBV. The transactivation of BATF is mediated by EBNA2 in a B-cell-specific manner and is duplicated in non-EBV-infected B cells by the expression of mammalian Notch proteins. In contrast to other target genes activated by EBNA2, the BATF gene encodes a member of the AP-1 family of transcription factors that functions as a negative regulator of AP-1 activity and as an antagonist of cell growth. A potential role for BATF in promoting EBV latency is supported by studies in which BATF was shown to negatively impact the expression of a BZLF1 reporter gene and to reduce the frequency of lytic replication in latently infected cells. The identification of BATF as a cellular target of EBV provides important new information on how programs of viral and cellular gene expression may be coordinated to promote viral latency and control lytic-cycle entry.

B-ATF functions as a negative regulator of AP-1 mediated transcription and blocks cellular transformation by Ras and Fos

B-ATF is a nuclear basic leucine zipper protein that belongs to the AP-1/ATF superfamily of transcription factors. Northern blot analysis reveals that the human B-ATF gene is expressed most highly in hematopoietic tissues. Interaction studies in vitro and in vivo show that the leucine zipper of B-ATF mediates dimerization with members of the Jun family of proteins. Chimeric proteins consisting of portions of B-ATF and the DNA binding domain of the yeast activator GAL4 do not stimulate reporter gene expression in mammalian cells, indicating that B-ATF does not contain a conventional transcription activation domain. Jun/B-ATF dimers display similar DNA binding profiles as Jun/Fos dimers, with a bias toward binding TRE (12-O-tetradecanolyphorbol-13-acetate-response element) over CRE (cyclic AMP-response element) DNA sites. B-ATF inhibits transcriptional activation of a reporter gene containing TRE sites in a dose-dependent manner, presumably by competing with Fos for Jun and forming transcriptionally inert Jun/B-ATF heterodimers. Stable expression of B-ATF in C3H10T1/2 cells does not reduce cell viability, but does result in a reduced cellular growth rate when compared to controls. This effect is dominant in the presence of the growth promoting effects of the H-Ras or the v-Fos oncoproteins, since expression of B-ATF restricts the efficiency of focus formation by these transforming agents. These findings demonstrate that B-ATF is a tissue-specific transcription factor with the potential to function as a dominant-negative to AP-1.

Increased chemokine receptor CCR7/EBI1 expression enhances the infiltration of lymphoid organs by adult T-cell leukemia cells

Adult T-cell leukemia (ATL) is characterized by infiltration of various tissues by circulating ATL cells, a finding often associated with a poor prognosis. Leukocyte migration from the circulation into tissues depends on integrin-mediated adhesion to the endothelium, and integrins are tightly regulated by several factors, such as chemokines. In this study, we focused on the interaction between chemokines and chemokine receptors on ATL cells to understand factors involved in ATL cell infiltration of lymphoid organs. We compared freshly isolated ATL cells from patients with and without lymphoid organ involvement for the expression of the chemokine receptor CCR7/EBI1, the functional receptor for secondary lymphoid-tissue chemokine (SLC), which is expressed at high levels by high endothelial venules of lymph nodes and Peyer's patches. Reverse transcriptase-polymerase chain reaction and flow cytometric analysis, using anti-CCR7 monoclonal antibody (CCR7.6B3), revealed that ATL cells from patients with lymphoid organ involvement expressed significantly more CCR7/EBI1 than control CD4+CD45RO+ T cells and ATL cells from patients without lymphoid organ involvement. Consequently, significantly more ATL cells from patients with lymphoid organ involvement than control CD4+CD45RO+ T cells and ATL cells from patients without lymphoid organ involvement adhered to surfaces coated with ICAM-1 and SLC or EBI1-ligand chemokine (ELC), another ligand for CCR7/EBI1, under static and flow conditions and migrated toward SLC or ELC at a low concentration (30 ng/ml). These findings suggest that increased CCR7/EBI1 expression plays a role in lymphoid organ infiltration of ATL cells. (Blood. 2000; 30-38)

Increased chemokine receptor CCR7/EBI1 expression enhances the infiltration of lymphoid organs by adult T-cell leukemia cells

Adult T-cell leukemia (ATL) is characterized by infiltration of various tissues by circulating ATL cells, a finding often associated with a poor prognosis. Leukocyte migration from the circulation into tissues depends on integrin-mediated adhesion to the endothelium, and integrins are tightly regulated by several factors, such as chemokines. In this study, we focused on the interaction between chemokines and chemokine receptors on ATL cells to understand factors involved in ATL cell infiltration of lymphoid organs. We compared freshly isolated ATL cells from patients with and without lymphoid organ involvement for the expression of the chemokine receptor CCR7/EBI1, the functional receptor for secondary lymphoid-tissue chemokine (SLC), which is expressed at high levels by high endothelial venules of lymph nodes and Peyer's patches. Reverse transcriptase-polymerase chain reaction and flow cytometric analysis, using anti-CCR7 monoclonal antibody (CCR7.6B3), revealed that ATL cells from patients with lymphoid organ involvement expressed significantly more CCR7/EBI1 than control CD4+CD45RO+ T cells and ATL cells from patients without lymphoid organ involvement. Consequently, significantly more ATL cells from patients with lymphoid organ involvement than control CD4+CD45RO+ T cells and ATL cells from patients without lymphoid organ involvement adhered to surfaces coated with ICAM-1 and SLC or EBI1-ligand chemokine (ELC), another ligand for CCR7/EBI1, under static and flow conditions and migrated toward SLC or ELC at a low concentration (30 ng/ml). These findings suggest that increased CCR7/EBI1 expression plays a role in lymphoid organ infiltration of ATL cells. (Blood. 2000; 30-38)

SFA-1/PETA-3 (CD151), a Member of the Transmembrane 4 Superfamily, Associates Preferentially with α5β1 Integrin and Regulates Adhesion of Human T Cell Leukemia Virus Type 1-Infected T Cells to Fibronectin

In this study we have analyzed the adhesion molecules associated with and the biologic function of SFA-1/PETA-3 (CD151) in human T cell leukemia virus type 1 (HTLV-1)-infected T cells and in freshly isolated adult T cell leukemia (ATL) cells using an anti-CD151 mAb. The anti-CD151 mAb coprecipitated α5β1 integrin from HTLV-1-infected T cells. Conversely, an anti-α5 integrin mAb coprecipitated CD151. The anti-CD151 mAb inhibited the adhesion of HTLV-1-infected T cells to fibronectin but did not have any effect on their adhesion to laminin, collagen type I, or collagen type IV. Moreover, antisense CD151 oligonucleotide-treated HTLV-1-infected T cells showed significant inhibition of adhesion to fibronectin. These findings showed that the CD151 molecule was associated with the α5β1 integrin molecule and that it enhanced α5β1 integrin-mediated adhesion to fibronectin. In addition, the expression levels of CD151, α4β1 integrin, and α5β1 integrin on ATL cells from lymph nodes of lymphoma-type ATL patients were significantly higher than those on circulating ATL cells from leukemia-type ATL patients. This suggests that the increased expression of these integrins may contribute to lymphoma formation through the adhesion of ATL cells to the extracellular matrix and dendritic cells, rather than contributing to transmigration.

Molecular cloning and expression of mouse homologue of SFA-1/PETA-3 (CD151), a member of the transmembrane 4 superfamily

We have isolated mouse SFA-1 (CD151) cDNA from a mouse myelomonocytic leukemia cell line, WEHI-3. Mouse CD151 mRNA comprises approximately 1.8 kb, has 253 amino acid residues with 93% identity to human CD151 and contains four putative transmembrane domains, a number of cysteine residues and one potential N-glycosylation site located at a site corresponding to that in human CD151. Mouse CD151 gene expression was observed in many cell types, but was either absent or present at a low level in brain and lymphoid cells and tissues, including thymus and spleen. The expression patterns of mouse and human CD151 genes are similar.