A C/EBP-like transcription factor, AGP/EBP, that binds to three distinct motifs in the 5'-flanking region of al-acid glycoprotein gene (AGP) has been identified. Here we report the cloning and properties of cDNA corresponding to mouse AGP/EBP. AGP/EBP and C/EBP share 87% amino acid sequence homology in the "leucine zipper" and its associated DNA-binding domains, while their sequences outside these domains and the sizes of their mRNAs are different. Unlike the limited expression of C/EBP in tissues and cells, AGP/EBP appears to be ubiquitously expressed in tissues like lung, spleen, kidney, heart, testis, and liver and cell lines like p388D1, 129P (hepatoma cell line of C3H/HeJ), FO (mouse myeloma), and L929. Antibody against cloned and expressed AGP/EBP which was raised in rabbits could recognize AGP/EBP from nuclear extract of a number of cells and tissues. On the basis of our findings about the structural relationship and the similarity of motif recognition, we propose that a family of C/EBP-like transcription factors exists. a,-Acid glycoprotein (AGP) is a liver-derived plasma glycoprotein which increases severalfold during acute-phase reaction (3-5, 37). AGP is transcriptionally regulated in rat, mouse, and human hepatocytes by interleukin-1 (IL-1) (31,34,36), hepatocyte-stimulating factor (beta interferon subtype 2 and IL-6) (6,13,16,24), and glucocorticoids (3,4,7,22,23,40). In the rat AGP gene, the hormonal stimulation by IL-1 and IL-6 is mediated by the distal regulatory element located at -5300 to -5150 (34), and the glucocorticoidresponsive element has been limited to positions -120 to -42 (7). The corresponding enhancer elements in the human and mouse AGP genes have not yet been defined. Unlike many glucocorticoid-responsive genes, such as those encoding the mouse mammary tumor virus (38, 40), human metallothionein (21), and tyrosine aminotransferase (33), the induction of AGP RNA by glucocorticoids is diminished in cells treated with protein synthesis inhibitor (e.g., cycloheximide) (3,22,23). It has been demonstrated that the rat AGP 5'-flanking region contains a DNA sequence (-121 to -107), exhibiting a high degree of homology to the glucocorticoid-responsive element consensus sequence 5'-GGTACAN3TGTTCT-3', which serves to specifically bind purified rat glucocorticoid receptor in vitro (22). A 15-bp oligonucleotide representing the rat AGP glucocorticoidresponsive element (5'-GGAACATTTTGTGCA-3') confers glucocorticoid responsiveness on a heterologous promoter; such regulation is not diminished by concurrent inhibition of protein synthesis. However, inclusion of the AGP sequences immediately downstream of the AGP glucocorticoid-responsive element (-106 to -42) renders the hormonal induction sensitive to inhibition of protein synthesis (22). DNase I footprinting with nuclear extracts prepared from HTC hepatoma cells indicates the presence of DNA-protein interactions spanning the region from -110 to -68 of the rat AGP gene (22).Three functional AGP genes (Agp-1, Agp-2, and Agp-3) have been isolated f...

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Abnormal regulation of apoptosis and cell proliferation is thought to be involved in tumor formation. The secreted Frizzled-related protein 2 (SFRP2) was detected in primary culture of canine mammary gland tumors but not in normal mammary tissues. Thus, to elucidate the role of SFRP2 in mammary tumorigenesis, we overexpressed SFRP2 in mammary gland tumor and MCF7 cells. The results indicated that SFRP2 is secreted and incorporated into the extracellular matrix (ECM) of the tumor and normal cells. In an attempt to understand the molecular basis underlying the interaction between SFRP2 and ECM, co-immunoprecipitation and cell adhesion assays were carried out. SFRP2 was found to be associated with the fibronectin-integrin protein complex and could promote cell adhesion. DNA fragmentation and caspase 3 activity analyses showed that the susceptibility of the cells to UV-induced apoptosis decreased in the context of SFRP2 overexpression. Upon disruption of the fibronectin-integrin connection, the antiapoptosis activity of SFRP2 was decreased. Moreover, SFRP2 was found to induce tumorous transformation in normal mammary epithelial cells and to inhibit apoptosis in a modified paracrine model. Collectively, our results emphasize the relevance of SFRP2 and ECM in mammary tumorigenesis and provide further insight into the mechanism of SFRP2 action.

Background: As an epigenetic regulator, the transcriptional intermediary factor 1β (TIF1β)/ KAP1/TRIM28) has been linked to gene expression and chromatin remodeling at specific loci by association with members of the heterochromatin protein 1 (HP1) family and various other chromatin factors. The interaction between TIF1β and HP1 is crucial for heterochromatin formation and maintenance. The HP1-box, PXVXL, of TIF1β is responsible for its interaction with HP1. However, the underlying mechanism of how the interaction is regulated remains poorly understood.

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Background: Salt-inducible kinase (SIK) 2 is an AMP-activated protein kinase family kinase that mediates hormonal and nutrient signaling but has no known link to cellular stress response. Results: p300/CBP and HDAC6 reciprocally regulates Lys-53 acetylation of SIK2, consequently impacting its activity and function in autophagosome maturation. Conclusion: SIK2 kinase activity, via a acetylation-based regulatory switch, contributes to autophagy progression. Significance: SIK2 may be linked to neurodegenerative or protein aggregate disorders.

Heterogeneous nuclear ribonucleoprotein K (hnRNP K), a component of hnRNP particles, is involved in several steps of gene expression regulation. Dengue (DEN) virus, a member of the Flaviviridae, is the primary cause of illnesses such as dengue fever, dengue hemorrhagic fever, and dengue shock syndrome. In mature DEN virus particles, the core protein is a structural protein that forms a nucleocapsid complex with genomic RNA. Very little of its biologic functions is known. Here, using an in vitro binding assay and coimmunoprecipitation analysis, we report a protein-protein interaction between the DEN virus core protein and hnRNP K. The C-terminal hydrophilic region of the DEN virus core protein, spanning amino acid residues 73 to 100, is required for such interaction. Results of glutathione-S transferase binding assays indicated that the core protein-hnRNP K interaction might be abolished in the presence of hnRNP K cognate nucleic acids. Furthermore, in a cotransfection experiment, the repressive effect of hnRNP K on C/EBPbeta-mediated transcription activation could be reversed by full-length DEN virus core protein but not by a truncated form containing amino acids 1-72. Our results suggest that, on DEN virus infection, the multiple functions of cellular hnRNP K may be affected by the virus core protein.