Hzf regulates adipogenesis through translational control of C/EBPalpha.

Adipocyte differentiation requires a well-defined programme of gene expression in which the transcription factor C/EBPalpha (CCAAT/enhancer-binding protein) has a central function. Here, we show that Hzf (haematopoietic zinc-finger), a previously identified p53 transcriptional target, regulates C/EBPalpha expression. Hzf is induced during differentiation of preadipocyte cell lines, and its suppression by short hairpin RNA disrupts adipogenesis. In Hzf's absence, expression of C/EBPalpha is severely impaired because of reduced translation of its mRNA. Hzf physically interacts with the 3' untranslated region of C/EBPalpha mRNA to enhance its translation. Taken together, these findings underscore a critical role of Hzf in the adipogenesis regulatory cascade.

The Runx3 transcription factor augments Th1 and down-modulates Th2 phenotypes by interacting with and attenuating GATA3.

Recently, it was reported that the expression of Runt-related transcription factor 3 (Runx3) is up-regulated in CD4(+) helper T cells during Th1 cell differentiation, and that Runx3 functions in a positive feed-forward manner with the T-box family transcription factor, T-bet, which is a master regulator of Th1 cell differentiation. The relative expression levels of IFN-gamma and IL-4 are also regulated by the Th2-associated transcription factor, GATA3. Here, we demonstrate that Runx3 was induced in Th2 as well as Th1 cells and that Runx3 interacted with GATA3 and attenuated GATA3 transcriptional activity. Ectopic expression of Runx3 in vitro in cultured cells or transgenic expression of Runx3 in mice accelerated CD4(+) cells to a Th1-biased population or down-modulated Th2 responses, in part by neutralizing GATA3. Our results suggest that the balance of Runx3 and GATA3 is one factor that influences the manifestation of CD4(+) cells as the Th1 or Th2 phenotypes.

Implication of p53-dependent cellular senescence related gene, TARSH in tumor suppression.

A novel target of NESH-SH3 (TARSH) was identified as a cellular senescence related gene in mouse embryonic fibroblasts (MEFs) replicative senescence, the expression of which has been suppressed in primary clinical lung cancer specimens. However, the molecular mechanism underlying the regulation of TARSH involved in pulmonary tumorigenesis remains unclear. Here we demonstrate that the reduction of TARSH gene expression by short hairpin RNA (shRNA) system robustly inhibited the MEFs proliferation with increase in senescence-associated beta-galactosidase (SA-beta-gal) activity. Using p53-/- MEFs, we further suggest that this growth arrest by loss of TARSH is evoked by p53-dependent p21(Cip1) accumulation. Moreover, we also reveal that TARSH reduction induces multicentrosome in MEFs, which is linked in chromosome instability and tumor development. These results suggest that TARSH plays an important role in proliferation of replicative senescence and may serve as a trigger of tumor development.

A novel p53-dependent apoptosis function of TARSH in tumor development.

A target of NESH-SH3/Abi3bp (TARSH) was originally identified as an SH3 domain-binding molecule of the NESH-SH3/Abi3 protein that is involved in Rac-dependent actin polymerization. In recent studies, TARSH gene expression was dramatically induced in mouse embryonic fibroblasts (MEFs) replicative senescence and suppressed in human lung carcinoma specimens and thyroid carcinomas. However, the molecular mechanism underlying the regulation of TARSH in tumorigenesis remains unclear. Here, we address a p53-dependent apoptosis function of the mouse TARSH gene using RNAi-mediated suppression of endogenous TARSH expression. Our results will be useful in the discovery of a novel therapeutic target in lung carcinoma.

Death-associated protein 3 regulates cellular senescence through oxidative stress response.

Death-associated protein 3 (DAP3) has been originally identified as a positive mediator of apoptosis. It has been revealed recently that the predominant localization of DAP3 to mitochondria implies its functional involvement in mitochondrial metabolism in addition to apoptosis. However, little is known about the molecular basis of these physiological functions of DAP3. Here, we demonstrate that DAP3 is reduced in both replicative and premature senescence induced by oxidative stress, and the DAP3 reduction induced by oxidative stress is observed mostly in a mitochondrial fraction. Using DAP3-specific short hairpin RNA (shRNA) in a clonogenic survival assay, we reveal that reduction of DAP3 induces resistance to oxidative stress and decreases intracellular reactive oxygen species (ROS) production. Furthermore, this strategy allows us to show that loss of DAP3 is involved in the avoidance of replicative senescence in mouse embryonic fibroblasts (MEFs). Thus, our study offers an insight into the potential regulatory function of mitochondrial DAP3 involved in cellular senescence.

Identification of transcripts expressed preferentially in hemocytes of Ciona intestinalis that can be used as molecular markers.

The immunity provided by ascidian hemocytes represents one prototype of innate immune function in vertebrates. However, there are currently no molecular markers of ascidian hemocytes. We accumulated a large number of ESTs of cDNAs derived from hemocytes of Ciona intestinalis, a cosmopolitan species of ascidian. By comparing these ESTs with those derived from other tissues and developmental stages of Ciona, we were able to extract 81 transcripts expressed abundantly and preferentially in hemocytes. Among them, the von Willebrand factor type A (vWA)-like and complement 6 (C6)-like transcripts were found to be expressed almost exclusively in hemocytes, based on RT-PCR analysis and whole mount in situ hybridization. We propose that vWA-like and C6-like can be used as molecular markers for Ciona hemocytes.