Acetylation-dependent regulation of Skp2 function

Aberrant Skp2 signaling has been implicated as a driving event in tumorigenesis. Although the underlying molecular mechanisms remain elusive, cytoplasmic Skp2 correlates with more aggressive forms of breast and prostate cancers. Here, we report that Skp2 is acetylated by p300 at K68 and K71, which is a process that can be antagonized by the SIRT3 deacetylase. Inactivation of SIRT3 leads to elevated Skp2 acetylation, which leads to increased Skp2 stability through impairment of the Cdh1-mediated proteolysis pathway. As a result, Skp2 oncogenic function is increased, whereby cells expressing an acetylation-mimetic mutant display enhanced cellular proliferation and tumorigenesis in vivo. Moreover, acetylation of Skp2 in the nuclear localization signal (NLS) promotes its cytoplasmic retention, and cytoplasmic Skp2 enhances cellular migration through ubiquitination and destruction of E-cadherin. Thus, our study identifies an acetylation-dependent regulatory mechanism governing Skp2 oncogenic function and provides insight into how cytoplasmic Skp2 controls cellular migration.     

Telomeric 3' overhangs derive from resection by Exo1 and Apollo and fill-in by POT1b-associated CST

A 3' overhang is critical for the protection and maintenance of mammalian telomeres, but its synthesis must be regulated to avoid excessive resection of the 5' end, which could cause telomere shortening. How this balance is achieved in mammals has not been resolved. Here, we determine the mechanism for 3' overhang synthesis in mouse cells by evaluating changes in telomeric overhangs throughout the cell cycle and at leading- and lagging-end telomeres. Apollo, a nuclease bound to the shelterin subunit TRF2, initiates formation of the 3' overhang at leading-, but not lagging-end telomeres. Hyperresection by Apollo is blocked at both ends by the shelterin protein POT1b. Exo1 extensively resects both telomere ends, generating transient long 3' overhangs in S/G2. CST/AAF, a DNA polα.primase accessory factor, binds POT1b and shortens the extended overhangs produced by Exo1, likely through fill-in synthesis. 3' overhang formation is thus a multistep, shelterin-controlled process, ensuring functional telomeric overhangs at chromosome ends.     

Spatial distribution of viruses associated with planktonic and attached microbial communities in hydrothermal environments

Viruses play important roles in marine surface ecosystems, but little is known about viral ecology and virus-mediated processes in deep-sea hydrothermal microbial communities. In this study, we examined virus-like particle (VLP) abundances in planktonic and attached microbial communities, which occur in physical and chemical gradients in both deep and shallow submarine hydrothermal environments (mixing waters between hydrothermal fluids and ambient seawater and dense microbial communities attached to chimney surface areas or macrofaunal bodies and colonies). We found that viruses were widely distributed in a variety of hydrothermal microbial habitats, with the exception of the interior parts of hydrothermal chimney structures. The VLP abundance and VLP-to-prokaryote ratio (VPR) in the planktonic habitats increased as the ratio of hydrothermal fluid to mixing water increased. On the other hand, the VLP abundance in attached microbial communities was significantly and positively correlated with the whole prokaryotic abundance; however, the VPRs were always much lower than those for the surrounding hydrothermal waters. This is the first report to show VLP abundance in the attached microbial communities of submarine hydrothermal environments, which presented VPR values significantly lower than those in planktonic microbial communities reported before. These results suggested that viral lifestyles (e.g., lysogenic prevalence) and virus interactions with prokaryotes are significantly different among the planktonic and attached microbial communities that are developing in the submarine hydrothermal environments.     

Ciliates expel environmental legionella-laden pellets to stockpile food

When Tetrahymena ciliates are cultured with Legionella pneumophila, the ciliates expel bacteria packaged in free spherical pellets. Why the ciliates expel these pellets remains unclear. Hence, we determined the optimal conditions for pellet expulsion and assessed whether pellet expulsion contributes to the maintenance of growth and the survival of ciliates. When incubated with environmental L. pneumophila, the ciliates expelled the pellets maximally at 2 days after infection. Heat-killed bacteria failed to produce pellets from ciliates, and there was no obvious difference in pellet production among the ciliates or bacterial strains. Morphological studies assessing lipid accumulation showed that pellets contained tightly packed bacteria with rapid lipid accumulation and were composed of the layers of membranes; bacterial culturability in the pellets rapidly decreased, in contrast to what was seen in ciliate-free culture, although the bacteria maintained membrane integrity in the pellets. Furthermore, ciliates newly cultured with pellets were maintained and grew vigorously compared with those without pellets. In contrast, a human L. pneumophila isolate killed ciliates 7 days postinfection in a Dot/Icm-dependent manner, and pellets harboring this strain did not support ciliate growth. Also, pellets harboring the human isolate were resuscitated by coculturing with amoebae, depending on Dot/Icm expression. Thus, while ciliates expel pellet-packaged environmental L. pneumophila for stockpiling food, the pellets packaging the human isolate are harmful to ciliate survival, which may be of clinical significance.     

Synthesis of organosoluble chitosan derivatives with polyphenolic side chains

A one-pot synthesis was used to produce chitosan derivatives with polyphenolic side chains via a regioselective phenolic coupling reaction. Under Mannich reaction conditions, treatment of chitosan with formaldehyde and methyl 2,4-dihydroxybenzoate gave N-(2,6-dihydroxy-3-methoxycarbonylphenyl)methylated chitosan in good yield (87%). Formation of a CC bond occurred regioselectively at the C(3) position of methyl 2,4-dihydroxybenzoate. Chitosan derivatives having various phenolic compounds as a side chain were easily synthesized in a similar manner. The chitosan derivatives showed good biodegradability and improved their solubility in methanol (9.8mgmL(-1)) and 2-methoxyethanol (> 10mgmL(-1)). The UV protection provided by the derivatives with phenolic benzophenone side chain was evaluated using UV spectra of polyethylene terephthalate and poly(vinyl butyral-co-vinyl alcohol-co-vinyl acetate) films coated with the derivatives and the derivatives absorbed effectively in the UV-A region (<60%). Self-aggregation of the chitosan derivatives with the phenolic side chain was observed by using a fluorescent probe in aqueous solution.     

Genome sequence of Pantoea agglomerans strain IG1

Pantoea agglomerans is a gram-negative bacterium that grows symbiotically with various plants. Here we report the 4.8-Mb genome sequence of P. agglomerans strain IG1. The lipopolysaccharides derived from P. agglomerans IG1 have been shown to be effective in the prevention of various diseases, such as bacterial or viral infection, lifestyle-related diseases. This genome sequence represents a substantial step toward the elucidation of pathways for production of lipopolysaccharides.     

RAS oncogenic signal upregulates EZH2 in pancreatic cancer

The neoplastic transformation by mutant RAS is thought to require remodeling of expression of an entire set of genes. However, the underlying mechanism for initiation of gene expression remodeling in tumorigenesis remains elusive. This study was aimed to define the oncogenic role of EZH2, a histone modifier protein that is induced by oncogenic mutant RAS, using pancreatic cancers of transgenic rats exogenously expressing human mutant RAS. Immunohistochemical observation of preneoplastic or cancerous lesions in the animal model suggested that upregulation of Ezh2 protein is an initiating event in pancreatic carcinogenesis. MEK-inhibition or Elk-1-knockdown downregulated EZH2, and MEK-inhibition or EZH2-knockdown restored expression of a tumor suppressor, RUNX3 in human and rat pancreatic cancer cells activated by the oncogenic RAS. Furthermore, Elk-1- or EZH2-knockdown inhibited growth of the cancer cells. These results strongly suggested that the oncogenic RAS upregulates EZH2 through MEK-ERK signaling, resulted in downregulation of tumor suppressors including RUNX3 in pancreatic carcinogenesis.     

Iron overload inhibits calcification and differentiation of ATDC5 cells

There is a little information about the effects of iron overload on cartilage metabolism. In the present study, we examined the effects of excess iron on the differentiation and mineralization of cultured chondrocytes, ATDC5 cells. We used ferric ammonium citrate (FAC) as a ferric ion donor and desferrioxamine (DFO) as a ferric ion chelator. Neither chemical affected the production of proteoglycan, a marker of an early stage of ATDC5 differentiation. In contrast, FAC inhibited the deposition of calcium, a late-stage event in chondrocyte differentiation, by ATDC5 cells in a dose-dependent manner, and DFO accelerated it. Energy dispersive X-ray spectroscopy/scanning electron microscope analysis revealed that the levels of iron and calcium in cells treated with FAC were increased and decreased, respectively. Furthermore, FAC inhibited the expression of matrix metalloproteinase 13 mRNA, another marker of late-stage chondrocyte differentiation. In addition, we found that the heavy and light chains of ferritin were expressed specifically at a late stage of ATDC5 differentiation, and the levels of both proteins were enhanced by the addition of iron. These results suggest that iron overload might give rise to osteopenia and arthritis by inhibiting chondrocyte differentiation and mineralization.     

Distribution of pink-pigmented facultative methylotrophs on leaves of vegetables

The distribution of pink-pigmented facultative methylotrophs (PPFMs) on the leaves of various vegetables was studied. All kinds of vegetable leaves tested gave pink-pigmented colonies on agar plates containing methanol as sole carbon source. The numbers of PPFMs on the leaves, colony-forming units (CFU)/g of fresh leaves, differed among the plants, although they were planted and grown at the same farm. Commercial green perilla, Perilla frutescens viridis (Makino) Makino, gave the highest counts of PPFMs (2.0-4.1×10(7) CFU/g) of all the commercial vegetable leaves tested, amounting to 15% of total microbes on the leaves. The PPFMs isolated from seeds of two varieties of perilla, the red and green varieties, exhibited high sequence similarity as to the 16S rRNA gene to two different Methylobacterium species, M. fujisawaense DSM5686(T) and M. radiotolerans JCM2831(T) respectively, suggesting that there is specific interaction between perilla and the PPFMs.     

Genetic organization of the hrp gene cluster in Acidovorax avenae strain N1141 and a novel effector protein that elicits immune responses in rice (Oryza sativa L.)

The immune system of plants consists of two main arms, pathogen-associated molecular pattern (PAMP)-triggered immunity (PTI) and effector-triggered immunity (ETI). The multiple effectors that trigger ETI are translocated into plant cells by the type III secretion system (T3SS) of pathogenic bacteria. The rice-avirulent N1141 strain of Acidovorax avenae causes ETI in rice, including hypersensitive response (HR) cell death. Sequence analysis indicated that the N1141 genome contains the hrp gene cluster (35.3 kb), including genes encoding the T3SS apparatus. The T3SS-defective N1141 mutant (NΔT3SS) did not cause HR cell death, suggesting that ETI is caused by translocation of effector proteins into rice cells via T3SS. Computational sequence analysis predicted that Lrp, HrpW, and HrpY are secreted by T3SS. The hrpY deletion mutant (NΔhrpY) did not cause ETI, suggesting that HrpY is an important effector of ETI in the interaction between A. avenae N1141 and rice.