Among the many mammalian secreted phospholipase A 2 (sPLA 2 ) enzymes, PLA2G3 (group III secreted phospholipase A 2 ) is unique in that it possesses unusual N-and C-terminal domains and in that its central sPLA 2 domain is homologous to bee venom PLA 2 rather than to other mammalian sPLA 2 s. To elucidate the in vivo actions of this atypical sPLA 2 , we generated transgenic (Tg) mice overexpressing human PLA2G3. Despite marked increases in PLA 2 activity and mature 18-kDa PLA2G3 protein in the circulation and tissues, PLA2G3 Tg mice displayed no apparent abnormality up to 9 months of age. However, alterations in plasma lipoproteins were observed in PLA2G3 Tg mice compared with control mice. In vitro incubation of low density (LDL) and high density (HDL) lipoproteins with several sPLA 2 s showed that phosphatidylcholine was efficiently converted to lysophosphatidylcholine by PLA2G3 as well as by PLA2G5 and PLA2G10, to a lesser extent by PLA2G2F, and only minimally by PLA2G2A and PLA2G2E. PLA2G3-modified LDL, like PLA2G5-or PLA2G10-treated LDL, facilitated the formation of foam cells from macrophages ex vivo. Accumulation of PLA2G3 was detected in the atherosclerotic lesions of humans and apoE-deficient mice. Furthermore, following an atherogenic diet, aortic atherosclerotic lesions were more severe in PLA2G3 Tg mice than in control mice on the apoE-null background, in combination with elevated plasma lysophosphatidylcholine and thromboxane A 2 levels. These results collectively suggest a potential functional link between PLA2G3 and atherosclerosis, as has recently been proposed for PLA2G5 and PLA2G10.

Eukaryotic transcription is regulated by multiple DNA elements, such as promoter-proximal elements, and is often combined with distal enhancer elements, which are recognized by several transcription factors. Core promoter regions often contain TATA, GC, and CCAAT boxes. The CCAAT box is one of the most typical elements for transcriptional activation. Several proteins, such as transcription factors of the C/EBP family and NF-I, have been shown to bind to CCAAT sequences. Nuclear factor Y (NF-Y) also binds to CCAAT boxes on many promoter regions (8). NF-Y is a well-conserved, ubiquitous transcription factor that consists of three subunits, NF-YA, NF-YB, and NF-YC, all of which are necessary for CCAAT box binding. NF-YB and NF-YC contain histone-folding motifs similar to H2A and H2B, respectively, and a tight complex of NF-YB and NF-YC associates with NF-YA (25). It has been reported that NF-Y associates with TATA box binding protein (TBP) (5) and several TBP-associated factors (TAFs) (11). NF-Y also interacts with p300/CBP, PCAF, and GCN5 and mediates histone acetylation on several promoters through these interactions (6,15,24,33).Osteoclast differentiation factor (ODF) is an essential factor for differentiation and activation of osteoclasts that is expressed on the osteoblast membrane (22,43). ODF is also known as TRANCE (tumor necrosis factor [TNF]-related activation-induced cytokine) and RANKL (receptor activator of NF-B ligand) (3, 39). ODF knockout mice exhibit typical osteoporosis with total occlusion of bone marrow space within endosteal bone (21) and also fail to develop mammary glands (10). In ODFϪ/Ϫ mice, mature osteoclasts are not found, whereas osteoclast progenitor cells are present. These observations indicate that ODF is an essential factor for developing mature osteoclasts and inducing bone resorption.ODF gene expression is induced by vitamin D3, parathyroid hormone (PTH), interleukin-1 (IL-1), TNF-␣, and PGE in primary osteoblasts or stromal cells (12,27,35,43). The mouse ODF promoter region contains a vitamin D3 response element (VDRE) (19,20). A heterodimer of vitamin D3 receptor (VDR) and retinoid X receptor (RXR) mediates vitamin D3 response (30). VDR-RXR transactivates target genes by recruiting transcriptional coactivators and mediators, such as the DRIP complex, which mediates transcriptional initiation, and the SRC-1/p300 complexes, which induce histone acetylation on target genes (13,31,32). The mouse ODF promoter also contains a CCAAT sequence near the transcriptional start site, but its significance is not known.In this report, we show that NF-Y is essential for transcriptional regulation of the ODF promoter. NF-Y exhibits a synergistic effect with vitamin D3 in activating this promoter. Knockdown analysis for an NF-Y subunit reveals that NF-Y is essential for the recruitment of RNAPII prior to induction but not for histone acetylation after vitamin D3 induction on the ODF promoter. Furthermore, NF-Y is also required for RNA-PII recruitment onto other CCAAT box-containing promoters, suc...

Nitrogen-containing bisphosphonates are pyrophosphate analogs that have long been the preferred prescription for treating osteoporosis. Although these drugs are considered inhibitors of prenylation and are believed to exert their effects on bone resorption by disrupting the signaling pathways downstream of prenylated small GTPases, this explanation seems to be insufficient. Because other classes of prenylation inhibitors have recently emerged as potential antiviral therapeutic agents, we first investigated here the effects of bisphosphonates on simian virus 40 and adenovirus infections and, to our surprise, found that viral infections are suppressed by bisphosphonates through a prenylationindependent pathway. By in-house affinity-capture techniques, dynamin-2 was identified as a new molecular target of bisphosphonates. We present evidence that certain bisphosphonates block endocytosis of adenovirus and a model substrate by inhibiting GTPase activity of dynamin-2. Hence, this study has uncovered a previously unknown mechanism of action of bisphosphonates and offers potential novel use for these drugs.