ZBTB34, a novel human BTB/POZ zinc finger protein, is a potential transcriptional repressor

Our work has identified a cancer-specific, cell surface and growth-related quinol oxidase with both NADH oxidase and protein disulfide-thiol interchange activities, a member of the ECTO-NOX protein family designated tNOX. We provide evidence for tNOX as an alternative drug target to COX-2 to explain the anticancer activity of COX inhibitors. Non-steroidal anti-inflammatory drugs (NSAIDS), piroxicam, aspirin, ibuprofen, naproxen and celecoxib all specifically inhibited tNOX activity of HeLa (human cervical carcinoma) and BT-20 (human mammary carcinoma) cells (IC₅₀ in the nanomolar range) without effect on ECTO-NOX activities of non-cancer MCF-10A mammary epithelial cells. With cancer cells, rofecoxib was less effective and two NSAIDS selective for COX-1 were without effect in inhibiting NOX activity. The IC₅₀ for inhibition of tNOX activity of HeLa cells and the IC₅₀ for inhibition of growth of HeLa cells in culture were closely correlated. The findings provide evidence for a new drug target to account for anticancer effects of NSAIDS that occur independent of COX-2.     

Identification and characterization of a novel Drosophila melanogaster glutathione S-transferase-containing FLYWCH zinc finger protein

Glutathione SH-transferase (GST) is a 25-kDa protein and a member of a large family that plays a critical role in the cellular homeostasis of all organisms. In this report, we describe a novel GST-containing protein identified and cloned from Drosophila. This 1045 amino acid protein possesses a zinc finger domain with a tandem array of four FLYWCH zinc finger motifs at its N-terminus and a C-terminal domain that shares a 46% homology with GST. The gene maps to chromosome 3 at position 84C6. Further characterization of this protein shows that it localizes to the cytoplasm of fly cells and is expressed through all stages of fly embryonic development. It binds to glutathione-S agarose beads in vitro. These results indicate that this new protein belongs to the GST family, thus named a Drosophila GST-containing FLYWCH zinc finger protein (dGFZF).     

ribbon encodes a novel BTB/POZ protein required for directed cell migration in Drosophila melanogaster

During development, directed cell migration is crucial for achieving proper shape and function of organs. One well-studied example is the embryonic development of the larval tracheal system of Drosophila, in which at least four signaling pathways coordinate cell migration to form an elaborate branched network essential for oxygen delivery throughout the larva. FGF signaling is required for guided migration of all tracheal branches, whereas the DPP, EGF receptor, and Wingless/WNT signaling pathways each mediate the formation of specific subsets of branches. Here, we characterize ribbon, which encodes a BTB/POZ-containing protein required for specific tracheal branch migration. In ribbon mutant tracheae, the dorsal trunk fails to form, and ventral branches are stunted; however, directed migrations of the dorsal and visceral branches are largely unaffected. The dorsal trunk also fails to form when FGF or Wingless/WNT signaling is lost, and we show that ribbon functions downstream of, or parallel to, these pathways to promote anterior-posterior migration. Directed cell migration of the salivary gland and dorsal epidermis are also affected in ribbon mutants, suggesting that conserved mechanisms may be employed to orient cell migrations in multiple tissues during development.     

Characterization of two novel nuclear BTB/POZ domain zinc finger isoforms. Association with differentiation of hippocampal neurons, cerebellar granule cells, and macroglia.

BTB/POZ (broad complex tramtrack bric-a-brac/poxvirus and zinc finger) zinc finger factors are a class of nuclear DNA-binding proteins involved in development, chromatin remodeling, and cancer. However, BTB/POZ domain zinc finger factors linked to development of the mammalian cerebral cortex, cerebellum, and macroglia have not been described previously. We report here the isolation and characterization of two novel nuclear BTB/POZ domain zinc finger isoforms, designated HOF(L) and HOF(S), that are specifically expressed in early hippocampal neurons, cerebellar granule cells, and gliogenic progenitors as well as in differentiated glia. During embryonic development of the murine cerebral cortex, HOF expression is restricted to the hippocampal subdivision. Expression coincides with early differentiation of presumptive CA1 and CA3 pyramidal neurons and dentate gyrus granule cells, with a sharp decline in expression at the CA1/subicular border. By using bromodeoxyuridine labeling and immunohistochemistry, we show that HOF expression coincides with immature non-dividing cells and is down-regulated in differentiated cells, suggesting a role for HOF in hippocampal neurogenesis. Consistent with the postulated role of the POZ domain as a site for protein-protein interactions, both HOF isoforms are able to dimerize. The HOF zinc fingers bind specifically to the binding site for the related promyelocytic leukemia zinc finger protein as well as to a newly identified DNA sequence.     

Isolation, characterization, and mapping of a novel human KRAB zinc finger protein encoding gene ZNF463

A novel human KRAB (Krüppel associated box) type zinc finger protein encoding gene, ZNF463, was obtained by mRNA differential display and RACE. It consists of 1904 nucleotides and encodes a protein of 463 amino acids with an amino-terminal KRAB domain and 12 carboxy-terminal C2H2 zinc finger units. The gene is mapped to chromosome 19q13.3 approximately 4 by FISH. As from Northern blot analysis ZNF463 is only expressed in testis, RT-PCR indicates that ZNF463 is expressed more highly in normal fertile adults than in fetus and azoospermic patients suggesting that it may play a role in human spermatogenesis.     

Cloning and characterization of a novel human gene encoding a zinc finger protein with 25 fingers

This study reports cloning and characterization of a human cDNA encoding a novel human zinc finger protein, ZFD25. ZFD25 cDNA is 6118 bp long and has an open reading frame of 2352 bp that encodes a 783 amino acid protein with 25 C2H2-type zinc fingers. The ZFD25 cDNA also contains a region with high sequence similarity to the Krüppel-associated box A and B domain in the 5'-untranslated region, suggesting that ZFD25 belongs to the Krüppel-associated box zinc finger protein family. The ZFD25 gene was localized to chromosome 7q11.2. Northern blot analysis showed that ZFD25 was expressed in a wide range of human organs. In cultured endothelial cells, the mRNA level was decreased upon serum starvation.     

The novel BTB/POZ and zinc finger factor Zbtb45 is essential for proper glial differentiation of neural and oligodendrocyte progenitor cells

Understanding the regulatory mechanisms controlling the fate decisions of neural stem cells (NSCs) is a crucial issue to shed new light on mammalian central nervous system (CNS) development in health and disease. We have investigated a possible role for the previously uncharacterized BTB/POZ-domain containing zinc finger factor Zbtb45 in the differentiation of NSCs and postnatal oligodendrocyte precursors. In situ hybridization histochemistry and RT-qPCR analysis revealed that Zbtb45 mRNA was ubiquitously expressed in the developing CNS in mouse embryos at embryonic day (E) 12.5 and 14.5. Zbtb45 mRNA knockdown in embryonic forebrain NSCs by siRNA resulted in a rapid decrease in the expression of oligodendrocyte-characteristic genes after mitogen (FGF2) withdrawal, whereas the expression of astrocyte-associated genes such as CD44 and GFAP increased compared to control. Accordingly, the number of astrocytes was significantly increased seven days after Zbtb45 siRNA delivery to NSCs, in contrast to the numbers of neuronal and oligodendrocyte-like cells. Surprisingly, mRNA knockdown of the Zbtb45-associated factor Med31, a subunit of the Mediator complex, did not result in any detectable effect on NSC differentiation. Similar to NSCs, Zbtb45 mRNA knockdown in oligodendrocyte precursors (CG-4) reduced oligodendrocyte maturation upon mitogen withdrawal associated with down-regulation of the mRNA expression and protein levels of markers for oligodendrocytic differentiation. Zbtb45 mRNA knockdown did not significantly affect proliferation or cell death in any of the cell types. Based on these observations, we propose that Zbtb45 is a novel regulator of glial differentiation.