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Structures of heterodimeric POZ domains of Miz1/BCL6 and Miz1/NAC1.

ABSTRACT: The POZ domain is an evolutionarily conserved protein-protein interaction domain that is found in approximately 40 mammalian transcription factors. POZ domains mediate both homodimerization and the heteromeric interactions of different POZ-domain transcription factors with each other. Miz1 is a POZ-domain transcription factor that regulates cell-cycle arrest and DNA-damage responses. The activities of Miz1 are altered by its interaction with the POZ-domain transcriptional repressors BCL6 and NAC1, and these interactions have been implicated in tumourigenesis in B-cell lymphomas and in ovarian serous carcinomas that overexpress BCL6 and NAC1, respectively. A strategy for the purification of tethered POZ domains that form forced heterodimers is described, and crystal structures of the heterodimeric POZ domains of Miz1/BCL6 and of Miz1/NAC1 are reported. These structures will be relevant for the design of therapeutics that target POZ-domain interaction interfaces.

SUBMITTER: Stead MA

PROVIDER: S-EPMC4259219 | biostudies-literature | 2014 Dec

REPOSITORIES: biostudies-literature

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Structures of heterodimeric POZ domains of Miz1/BCL6 and Miz1/NAC1.

Stead Mark Alexander MA Wright Stephanie Claire SC

Acta crystallographica. Section F, Structural biology communications 20141114 Pt 12

The POZ domain is an evolutionarily conserved protein-protein interaction domain that is found in approximately 40 mammalian transcription factors. POZ domains mediate both homodimerization and the heteromeric interactions of different POZ-domain transcription factors with each other. Miz1 is a POZ-domain transcription factor that regulates cell-cycle arrest and DNA-damage responses. The activities of Miz1 are altered by its interaction with the POZ-domain transcriptional repressors BCL6 and NAC ...[more]

PMID: 25484205

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Nac1 interacts with the POZ-domain transcription factor, Miz1.

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Structure of the human Nac1 POZ domain.

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NAC1 attenuates BCL6 negative autoregulation and functions as a BCL6 coactivator of FOXQ1 transcription in cancer cells.

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The ansamycin antibiotic, rifamycin SV, inhibits BCL6 transcriptional repression and forms a complex with the BCL6-BTB/POZ domain.

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BCL6 suppression of BCL2 via Miz1 and its disruption in diffuse large B cell lymphoma.

Project description:The BCL6 proto-oncogene encodes a transcriptional repressor that is required for germinal center (GC) formation and whose deregulation by genomic lesions is implicated in the pathogenesis of GC-derived diffuse large B cell lymphoma (DLBCL) and, less frequently, follicular lymphoma (FL). The biological function of BCL6 is only partially understood because no more than a few genes have been functionally characterized as direct targets of BCL6 transrepression activity. Here we report that the anti-apoptotic proto-oncogene BCL2 is a direct target of BCL6 in GC B cells. BCL6 binds to the BCL2 promoter region by interacting with the transcriptional activator Miz1 and suppresses Miz1-induced activation of BCL2 expression. BCL6-mediated suppression of BCL2 is lost in FL and DLBCL, where the 2 proteins are pathologically coexpressed, because of BCL2 chromosomal translocations and other mechanisms, including Miz1 deregulation and somatic mutations in the BCL2 promoter region. These results identify an important function for BCL6 in facilitating apoptosis of GC B cells via suppression of BCL2, and suggest that blocking this pathway is critical for lymphomagenesis.

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Effect of Miz1 POZ domain deletion on expression profiles of B and T leukemia cells

Project description:Acute lymphoblastic leukemia (ALL) is an aggressive blood cancer mainly affecting children. Relapse rates are high and toxic chemotherapies that block DNA replication and induce DNA damage cause health problems later in life, underlining the need for improved therapies. c-Myc is a transcription factor that is hyperactive in a large proportion of cancers including leukemia but is difficult to target in therapy. We show that ablation of the function of the BTB/POZ domain factor Miz-1, an important co-factor of c-Myc, significantly delays T- and B-ALL/lymphoma in mice and interferes with c-Myc oncogenic transcriptional activity. Leukemic cells that still emerge in this system activate DNA replication pathways, which are those targeted by current chemotherapeutic drugs such as cytarabine. We found that the combination of acute ablation of the Miz-1 POZ domain enhances the effect of cytarabine treatment. This combination was effective in both Eµ-Myc and Notch ICN driven leukemia models and prolonged survival of tumor bearing animals by accelerating apoptosis of leukemic cells. These observations suggest that targeting Miz-1 could render current ALL chemotherapies more effective with a better outcome for patients.

2019-09-30 | GSE120001 | GEO

All in the family: the BTB/POZ, KRAB, and SCAN domains.

Project description: Not available

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BTB/POZ zinc finger protein ZBTB16 inhibits breast cancer proliferation and metastasis through upregulating ZBTB28 and antagonizing BCL6/ZBTB27.

Project description:BackgroundBreast cancer remains in urgent need of reliable diagnostic and prognostic markers. Zinc finger and BTB/POZ domain-containing family proteins (ZBTBs) are important transcription factors functioning as oncogenes or tumor suppressors. The role and regulation of ZBTB16 in breast cancer remain to be established.MethodsReverse-transcription PCR and methylation-specific PCR were applied to detect expression and methylation of ZBTB16 in breast cancer cell lines and tissues. The effects of ZBTB16 in breast cancer cells were examined via cell viability, CCK8, Transwell, colony formation, and flow cytometric assays. Xenografts and immunohistochemistry analyses were conducted to determine the effects of ZBTB16 on tumorigenesis in vivo. The specific mechanisms of ZBTB16 were further investigated using Western blot, qRT-PCR, luciferase assay, and co-IP.ResultsZBTB16 was frequently downregulated in breast cancer cell lines in correlation with its promoter CpG methylation status. Restoration of ZBTB16 expression led to induction of G2/M phase arrest and apoptosis, inhibition of migration and invasion, reversal of EMT, and suppression of cell proliferation, both in vitro and in vivo. Furthermore, ectopically expressed ZBTB16 formed heterodimers with ZBTB28 or BCL6/ZBTB27 and exerted tumor suppressor effects through upregulation of ZBTB28 and antagonistic activity on BCL6.ConclusionsLow expression of ZBTB16 is associated with its promoter hypermethylation and restoration of ZBTB16 inhibits tumorigenesis. ZBTB16 functions as a tumor suppressor through upregulating ZBTB28 and antagonizing BCL6. Our findings also support the possibility of ZBTB16 being a prognostic biomarker for breast cancer.

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