Characteristics of radish lines and hybrids from the spectrum of multiple molecular forms of enzymes

We characterized radish lines from a genetic collection on the basis of six enzyme systems, identified genes controlling these enzymes, and examined joint inheritance of some biochemical and morphological traits.     

Xanthones from the bark of Garcinia merguensis

The bark of Garcinia merguensis yielded 10 xanthones, merguenone, 1,5-dihydroxy-6'-methyl-6'-(4-methyl-3-pentenyl)-pyrano(2',3':3,2)-xanthone, subelliptenone H, 8-deoxygartanin, rheediaxanthone A, morusignin G, 6-deoxyjacareubin, 1,3,5-trihydroxy-4,8-di(3-methylbut-2-enyl)-xanthone, rheediachromenoxanthone and 6-deoxyisojacareubin. The structure of merguenone was determined using spectroscopic techniques, mainly 1D and 2D NMR spectroscopy.     

Deletion of the PAT1 gene affects translation initiation and suppresses a PAB1 gene deletion in yeast

The yeast poly(A) binding protein Pab1p mediates the interactions between the 5' cap structure and the 3' poly(A) tail of mRNA, whose structures synergistically activate translation in vivo and in vitro. We found that deletion of the PAT1 (YCR077c) gene suppresses a PAB1 gene deletion and that Pat1p is required for the normal initiation of translation. A fraction of Pat1p cosediments with free 40S ribosomal subunits on sucrose gradients. The PAT1 gene is not essential for viability, although disruption of the gene severely impairs translation initiation in vivo, resulting in the accumulation of 80S ribosomes and in a large decrease in the amounts of heavier polysomes. Pat1p contributes to the efficiency of translation in a yeast cell-free system. However, the synergy between the cap structure and the poly(A) tail is maintained in vitro in the absence of Pat1p. Analysis of translation initiation intermediates on gradients indicates that Pat1p acts at a step before or during the recruitment of the 40S ribosomal subunit by the mRNA, a step which may be independent of that involving Pab1p. We conclude that Pat1p is a new factor involved in protein synthesis and that Pat1p might be required for promoting the formation or the stabilization of the preinitiation translation complexes.     

Effects of angiotensin II on the acrosome reaction in equine spermatozoa

Angiotensin II is a hormone with a wide array of physiological effects that exerts its effect via interaction with two major subtypes of receptor. The results of this study show that angiotensin II (from 1 to 100 nmol l(-1)) initiates acrosomal exocytosis in equine spermatozoa that have undergone capacitation in vitro in a TALP-TEST (Tyrode's albumin lactate pyruvate; 188.7 mmol TES l(-1), 84.8 mmol Tris l(-1)) buffer with cAMP. The acrosome reaction and sperm viability were assessed with fluorescein isothiocyanate-Pisum sativum agglutinin (FITC-PSA) and Hoechst 33258, respectively. The initiation of the acrosome reaction by angiotensin II was strongly inhibited by losartan, a specific angiotensin II type 1 receptor antagonist. Although angiotensin II as well as progesterone both initiated the acrosome reaction in equine spermatozoa, there was no synergistic effect when both agonists were added simultaneously. Initiation of acrosomal exocytosis by angiotensin II was accompanied by a rapid and transient calcium influx that was assessed in capacitated spermatozoa loaded with Fura-2AM. In addition, the angiotensin II-mediated calcium influx was inhibited when spermatozoa were preincubated with losartan. Western blotting with an antibody against angiotensin II type 1 receptor detected a major sperm protein of 60 kDa. Indirect immunofluorescence of non-capacitated spermatozoa with the angiotensin II type 1 receptor antibody revealed labelling in the midpiece and tail. In capacitated spermatozoa, the angiotensin II type 1 receptor was localized mainly over the anterior region of the sperm head, the equatorial segment and occasionally on the postacrosomal region in addition to the sperm tail. In conclusion, this study demonstrated the ability of angiotensin II to stimulate the acrosome reaction in capacitated equine spermatozoa. This effect is mediated via the angiotensin II type 1 receptor and is accompanied by an increase in intracellular calcium.     

A RecA Protein Surface Required for Activation of DNA Polymerase V

DNA polymerase V (pol V) of Escherichia coli is a translesion DNA polymerase responsible for most of the mutagenesis observed during the SOS response. Pol V is activated by transfer of a RecA subunit from the 3''-proximal end of a RecA nucleoprotein filament to form a functional complex called DNA polymerase V Mutasome (pol V Mut). We identify a RecA surface, defined by residues 112-117, that either directly interacts with or is in very close proximity to amino acid residues on two distinct surfaces of the UmuC subunit of pol V. One of these surfaces is uniquely prominent in the active pol V Mut. Several conformational states are populated in the inactive and active complexes of RecA with pol V. The RecA D112R and RecA D112R N113R double mutant proteins exhibit successively reduced capacity for pol V activation. The double mutant RecA is specifically defective in the ATP binding step of the activation pathway. Unlike the classic non-mutable RecA S117F (recA1730), the RecA D112R N113R variant exhibits no defect in filament formation on DNA and promotes all other RecA activities efficiently. An important pol V activation surface of RecA protein is thus centered in a region encompassing amino acid residues 112, 113, and 117, a surface exposed at the 3''-proximal end of a RecA filament. The same RecA surface is not utilized in the RecA activation of the homologous and highly mutagenic RumA''₂B polymerase encoded by the integrating-conjugative element (ICE) R391, indicating a lack of structural conservation between the two systems. The RecA D112R N113R protein represents a new separation of function mutant, proficient in all RecA functions except SOS mutagenesis.     

Utilization of the Soft Agar Colony Formation Assay to Identify Inhibitors of Tumorigenicity in Breast Cancer Cells

Given the inherent difficulties in investigating the mechanisms of tumor progression in vivo, cell-based assays such as the soft agar colony formation assay (hereafter called soft agar assay), which measures the ability of cells to proliferate in semi-solid matrices, remain a hallmark of cancer research. A key advantage of this technique over conventional 2D monolayer or 3D spheroid cell culture assays is the close mimicry of the 3D cellular environment to that seen in vivo. Importantly, the soft agar assay also provides an ideal tool to rigorously test the effects of novel compounds or treatment conditions on cell proliferation and migration. Additionally, this assay enables the quantitative assessment of cell transformation potential within the context of genetic perturbations. We recently identified peptidylarginine deiminase 2 (PADI2) as a potential breast cancer biomarker and therapeutic target. Here we highlight the utility of the soft agar assay for preclinical anti-cancer studies by testing the effects of the PADI inhibitor, BB-Cl-amidine (BB-CLA), on the tumorigenicity of human ductal carcinoma in situ (MCF10DCIS) cells.     

Cancer incidence and mortality after low-dose radiation exposure: epidemiological aspects

Current recommendations for limiting exposure to ionizing radiation are based on the linear-no-threshold (LNT) model for radiation carcinogenesis under which every dose, no matter how low, carries with it some cancer risk. In this review, epidemiological evidences are discussed that the LNT hypothesis is incorrect at low doses. A large set of data was accumulated that showed that cancer risk after ordinarily encountered radiation exposure (natural background radiation, medical X-rays, etc.) is much lower than projections based on the LNT model. The discovery of the low-level radiation hormesis (stimulating effect) implies a non-linear dose-response curve in the low-dose region. The further studies in this field will provide new insights about the mechanisms of radiation carcinogenesis.