Regulation of Wnt signaling by the tumor suppressor adenomatous polyposis coli does not require the ability to enter the nucleus or a particular cytoplasmic localization

Wnt signaling plays key roles in development and disease. The tumor suppressor adenomatous polyposis coli (APC) is an essential negative regulator of Wnt signaling. Its best-characterized role is as part of the destruction complex, targeting the Wnt effector β-catenin (βcat) for phosphorylation and ultimate destruction, but several studies suggested APC also may act in the nucleus at promoters of Wnt-responsive genes or to shuttle βcat out for destruction. Even in its role in the destruction complex, APC's mechanism of action remains mysterious. We have suggested APC positions the destruction complex at the appropriate subcellular location, facilitating βcat destruction. In this study, we directly tested APC's proposed roles in the nucleus or in precisely localizing the destruction complex by generating a series of APC2 variants to which we added tags relocalizing otherwise wild-type APC to different cytoplasmic locations. We tested these for function in human colon cancer cells and Drosophila embryos. Strikingly, all rescue Wnt regulation and down-regulate Wnt target genes in colon cancer cells, and most restore Wnt regulation in Drosophila embryos null for both fly APCs. These data suggest that APC2 does not have to shuttle into the nucleus or localize to a particular subcellular location to regulate Wnt signaling.     

Programming obesity and poor fitness: the long-term impact of childhood television

Objective: To assess whether the long‐term effects of childhood television viewing on BMI and cardiorespiratory fitness are mediated by adult viewing. Methods and Procedures: This prospective study included an unselected birth cohort of 1,037 participants (535 men) born in Dunedin, New Zealand in 1972/1973. Hours of television viewing on weekdays were reported at ages 5, 7, 9, 11, 13, 15, and 32 years. BMI and cardiorespiratory fitness were measured at age 32 years. Results: Both childhood and adult television viewing times were significantly associated with higher BMI and lower cardiorespiratory fitness at age 32 years. Childhood television viewing was a better predictor of adult BMI and fitness than adult viewing and remained a significant predictor of these outcomes after adjusting for adult viewing time. After adjusting for adult viewing, the odds (95% confidence interval) of adult obesity increased by a factor of 1.25 (1.01, 1.53) and poor fitness increased by a factor of 1.40 (1.16, 1.70) for each hour of mean weekday television viewing during childhood. Discussion: The association between childhood television viewing and obesity and poor fitness in adulthood is not mediated by adult viewing. The detrimental health effects of watching too much television during childhood persist into adulthood. Attempts to reduce adult obesity and poor fitness by modifying television viewing habits need to begin in childhood.     

Changes in soil phosphorus fractions following positive and negative phosphorus balances for long periods

The effect of phosphorus (P) balance (addition, in both fertilizers and farmyard manure (FYM), minus removal in crops) on eight soil P fractions determined by sequential extraction, was measured on archived soils from various long-term experiments run by Rothamsted Experimental Station in the United Kingdom. It has been established unequivocally that, for all the soils investigated, no one of the eight P fractions was increased or decreased during long periods of P addition or depletion, respectively. However, changes were mainly in the resin (24–30%) and the inorganic (P_i) component of the four fractions extracted sequentially by 0.5 M NaHCO₃, 0.1 M NaOH, 1.0 M NaOH, 0.5 M H₂SO₄ (41–60%). For the sandy loam there were also consistent changes in the organic (P_o) fraction (25%), especially that extracted by bicarbonate, presumably because the soil contained only a little clay and presumably had low sorption capacity. When the soils were cropped without P addition the largest proportional change was in the P extracted by resin, 0.5 M NaHCO₃ and 0.1 M NaOH, suggesting that the P in these fractions is readily available, or has the potential to become available, for crop growth. This was supported by changes in the overall P balance. On the heavier textured soils, 50–80% of the change in total soil P (P_T) was in these fractions; on the sandy soil this increased to more than 90%. The change in the sum of the first five fractions accounted, on average, for 90% of the P balance. However these changes in the P in the plough layer frequently left large amounts of P unaccounted for in some of the excessively P enriched soils. The amount of P_i extracted by resin and bicarbonate (P_i(r+b)) ranged between 14 and 50% of the sum of the P_i fractions. Soils with the lower percentages were those known to be most responsive to P fertilizers. P_i(r+b) accounted for an average of 70% of the P balance (negative) in P depleting soils where crop offtake was not offset or exceeded by annual P additions (positive balance). The ratio between P_i(r+b) and P_i(sum) could be a guide in defining soils deficient in P and those which are excessively enriched.     

Large-scale latitudinal distribution of Trichodesmium spp. in the Atlantic Ocean

The Atlantic Meridional Transect (AMT) programme is a seriesof bi-annual cruises between the Falkland Islands (50°S)and the UK (50°N). Measurements of the abundance of theN₂-fixing, colonial cyanobacterium Trichodesmium along thistransect in the years 1995–1999 reveal that it is especiallyabundant between 0 and 15°N, but by contrast almost completelyabsent between 5 and 30°S. The cruise path between 0 and15°N lies close to 20°W, on the African (eastern) sideof the Atlantic. The maximum colony abundances we observed (     

Enzymic synthesis of lignin precursors. Purification of properties of the S-adenosyl-l-methionine: caffeic acid 3-O- methyltransferase from soybean cell suspension cultures.

A 3-O-methyltransferase which catalyzes the methylation of caffeic acid to ferulic acid using S-adenosyl-l-methionine as methyl donor has been isolated and purified about 60-fold from cell suspension cultures of soybean (Glycine max L., var. Mandarin). The enzyme utilized, in addition to caffeic acid (K_m = 133 μM), 5-hydroxyferulic acid (K_m = 55 μM), 3,4,5-trihydroxy-cinnamic acid (K_m = 100 μM), and protocatechualdehyde (K_m = 50 μM) as substrates. Methylation proceeded only in the meta position. The enzyme was unable to catalyze the methylation of ferulic acid, of ortho-, meta-, and para-coumaric acids, and of the flavonoid compounds quercetin and luteolin. The methylation of caffeic acid and 5-hydroxyferulic acid showed a pH optimum at 6.5–7.0. No stimulation of the reaction velocity was observed when Mg²⁺ ions were added. EDTA did not inhibit the reaction. The K_m for S-adencsyl-l-methionine was 15 μm. S-Adenosyl-l-homocysteine was a potent competitive inhibitor of S-adenosyl-l-methionine (K_i = 6.9 μM).     

Homopolymeric tract heteroplasmy in mtDNA from tissues and single oocytes: support for a genetic bottleneck.

While mtDNA polymorphisms at single base positions are common, the overwhelming majority of the mitochondrial genomes within a single individual are usually identical. When there is a point-mutation difference between a mother and her offspring, there may be a complete switching of mtDNA type within a single generation. It is generally assumed that there is a genetic bottleneck whereby a single or small number of founder mtDNA(s) populate the organism, but it is not known at which stages the restriction/amplification of mtDNA subtype(s) occur, and this uncertainty impedes antenatal diagnosis for mtDNA disorders. Length polymorphisms in homopolymeric tracts have been demonstrated in the large noncoding region of mtDNA. We have developed a new method, T-PCR (trimmed PCR), to quantitate heteroplasmy for two of these tracts (D310 and D16189). D310 variation is sufficient to indicate clonal origins of tissues and single oocytes. Tissues from normal individuals often possessed more than one length variant (heteroplasmy). However, there was no difference in the pattern of the length variants between somatic tissues in any control individual when bulk samples were taken. Oocytes from normal women undergoing in vitro fertilization were frequently heteroplasmic for length variants, and in two cases the modal length of the D310 tract differed in individual oocytes from the same woman. These data suggest that a restriction/amplification event, which we attribute to clonal expansion of founder mtDNA(s), has occurred by the time oocytes are mature, although further segregation may occur at a later stage. In contrast to controls, the length distribution of the D310 tract varied between tissues in a patient with heteroplasmic mtDNA rearrangements, suggesting that these mutants influence segregation. These findings have important implications for the genetic counselling of patients with pathogenic mtDNA mutations.