BRCA1 tumor suppression depends on BRCT phosphoprotein binding, but not its E3 ligase activity

Germline mutations of the breast cancer 1 (BRCA1) gene are a major cause of familial breast and ovarian cancer. The BRCA1 protein displays E3 ubiquitin ligase activity, and this enzymatic function is thought to be required for tumor suppression. To test this hypothesis, we generated mice that express an enzymatically defective Brca1. We found that this mutant Brca1 prevents tumor formation to the same degree as does wild-type Brca1 in three different genetically engineered mouse (GEM) models of cancer. In contrast, a mutation that ablates phosphoprotein recognition by the BRCA C terminus (BRCT) domains of BRCA1 elicits tumors in each of the three GEM models. Thus, BRCT phosphoprotein recognition, but not the E3 ligase activity, is required for BRCA1 tumor suppression.     

BOLD responses reflecting dopaminergic signals in the human ventral tegmental area

Current theories hypothesize that dopamine neuronal firing encodes reward prediction errors. Although studies in nonhuman species provide direct support for this theory, functional magnetic resonance imaging (fMRI) studies in humans have focused on brain areas targeted by dopamine neurons [ventral striatum (VStr)] rather than on brainstem dopaminergic nuclei [ventral tegmental area (VTA) and substantia nigra]. We used fMRI tailored to directly image the brainstem. When primary rewards were used in an experiment, the VTA blood oxygen level-dependent (BOLD) response reflected a positive reward prediction error, whereas the VStr encoded positive and negative reward prediction errors. When monetary gains and losses were used, VTA BOLD responses reflected positive reward prediction errors modulated by the probability of winning. We detected no significant VTA BOLD response to nonrewarding events.     

Attention reduction and suppressed direct-current potentials in the human brain

Distraction suppresses direct-current potentials (contingent negative variation) recorded from the human scalp. This reduction is accompanied by retarded reaction time. Contingent negative variation and reaction time appear to reflect a common process, attention.     

酿酒酵母中磷脂合成相关基因突变对细胞自噬和液泡形态的影响

[目的]探讨酿酒酵母中磷脂合成相关基因突变对细胞自噬和液泡形态的影响.[方法]通过尼罗红染色观察酵母中磷脂合成相关基因突变后脂滴的形态;用绿色荧光蛋白(GFP)标记细胞自噬蛋白Atg8后,采用荧光显微镜和免疫印迹试验检测突变体细胞自噬的发生情况,并使用荧光染料FM4-64检测液泡形态;此外,检测相关突变体对吩嗪-1-羧酸(申嗪霉素)的敏感性.[结果]在营养有限条件下,酿酒酵母中磷脂合成相关基因突变体中脂滴的大小或数量受到不同程度的影响,但细胞自噬在常规检测条件下正常;其中磷脂酸胞苷转移酶编码基因CDS1突变导致液泡形态异常(碎片化),而其他磷脂合成相关基因突变不影响液泡形态;回补CDS1后,cds1-DAmP突变体中液泡形态恢复正常;此外,cds 1-DAmP突变体对吩嗪-1-羧酸处理更为敏感.[结论]酿酒酵母中脂滴和液泡形态异常不一定影响细胞自噬的正常进行,但可能影响其对外界环境的响应.     

Antibodies to clathrin inhibit endocytosis but not recycling to the trans Golgi network in vitro

Mannose 6-phosphate receptors carry newly synthesized lysosomal enzymes from the trans Golgi network (TGN) to prelysosomes and then return to the TGN to carry out another round of lysosomal enzyme delivery. Although clathrin-coated vesicles mediate the export of mannose 6-phosphate receptors from the TGN, nothing is known about the transport vesicles used to carry these receptors back to the TGN. Two different in vitro assays used in this study show that an antibody that interferes with clathrin assembly blocks receptor-mediated endocytosis of transferrin, but has no effect on the recycling of the 300-kilodalton mannose 6-phosphate receptor from prelysosomes to the TGN. These results suggest that the transport of mannose 6-phosphate receptors from prelysosomes to the TGN does not involve clathrin.     

Mycoplasma leachii causes polyarthritis in calves via the blood route but is not associated with pneumonia

Mycoplasma leachii was initially isolated from arthritic calves in South Queensland, Australia, and its ability to cause clinical polyarthritis in calves was demonstrated by experimental infection. However, the source of M. leachii infection in calves and its means of spreading are not well known. In this study, one-month-old calves were inoculated with cultures of M. leachii or joint fluid (collected from M. leachii-infected calves) through the intraarticular, intravenous, intratracheal, intranasal or oral routes. Multidisciplinary procedures, including clinical assessment, etiology assessment, pathology and immunohistochemistry (IHC), were used to evaluate the pathogenicity of M. leachii in calves and to elucidate the transmission route of M. leachii infection in calves. The results showed that all calves inoculated intraarticularly with cultured GN407 or joint fluid and two-thirds of the calves inoculated intravenously with joint fluid developed severe polyarthritis, and the M. leachii antigen was detected in the joints of all infected calves by IHC and PCR. In contrast, calves inoculated with cultured M. leachii or joint fluid through the intratracheal, intranasal or oral routes did not show any M. leachii infection in the clinical assessment, etiology assessment, or pathology and IHC results. These results indicated that polyarthritis caused by M. leachii in calves is transmitted via the blood route; however, this disease is not transmitted through the respiratory or digestive routes. In addition, the M. leachii antigen was not detected in the lungs of all the inoculated calves using IHC and PCR, indicating that M. leachii is not associated with pneumonia, even in the calves inoculated through the respiratory duct. These findings are important information for the prevention and control of calf polyarthritis caused by M. leachii.     

Divided by cytochrome oxidase: a map of the projections from V1 to V2 in macaques

Current models partition the primate visual system into dorsal (magno) and ventral (parvo, konio) streams. Perhaps the strongest evidence for this idea has come from the pattern of projections between the primary visual area (V1) and the second visual area (V2). Prior studies describe three distinct pathways: magno to thick stripes, parvo to pale stripes, and konio to thin stripes. We now demonstrate that V1 output arises from just two sources: patch columns and interpatch columns. Patch columns project to thin stripes and interpatch columns project to pale and thick stripes. Projection of interpatches to common V2 stripe types (pale and thick) merges parvo and magno inputs, making it likely that these functional channels are distributed strongly to both dorsal and ventral streams.     

BSKs mediate signal transduction from the receptor kinase BRI1 in Arabidopsis

Brassinosteroids (BRs) bind to the extracellular domain of the receptor kinase BRI1 to activate a signal transduction cascade that regulates nuclear gene expression and plant development. Many components of the BR signaling pathway have been identified and studied in detail. However, the substrate of BRI1 kinase that transduces the signal to downstream components remains unknown. Proteomic studies of plasma membrane proteins lead to the identification of three homologous BR-signaling kinases (BSK1, BSK2, and BSK3). The BSKs are phosphorylated by BRI1 in vitro and interact with BRI1 in vivo. Genetic and transgenic studies demonstrate that the BSKs represent a small family of kinases that activate BR signaling downstream of BRI1. These results demonstrate that BSKs are the substrates of BRI1 kinase that activate downstream BR signal transduction.     

Malignant activation of a K-ras oncogene in lung carcinoma but not in normal tissue of the same patient

A single genetic alteration, a guanine-to-cytosine transversion, is responsible for the acquisition of malignant properties by K-ras genes of two human tumor cell lines established from carcinomas of the bladder (A1698) and lung (A2182). As a consequence, arginine instead of the normal glycine is incorporated into the K-ras-coded p21 proteins at amino acid position 12. This mutation creates a restriction enzyme polymorphism that can be used to screen human cells for transforming K-ras genes. This approach was used to identify the mutational event responsible for the malignant activation of a K-ras oncogene in a squamous cell lung carcinoma of a 66-year-old man; this point mutation was not present in either the normal bronchial or parenchymal tissue or in the blood lymphocytes. Hence, malignant activation of a ras oncogene appears to be specifically associated with the development of a human neoplasm.     

Role of the kinase MST2 in suppression of apoptosis by the proto-oncogene product Raf-1

The ablation of the protein kinase Raf-1 renders cells hypersensitive to apoptosis despite normal regulation of extracellular signal-regulated kinases, which suggests that apoptosis protection is mediated by a distinct pathway. We used proteomic analysis of Raf-1 signaling complexes to show that Raf-1 counteracts apoptosis by suppressing the activation of mammalian sterile 20-like kinase (MST2). Raf-1 prevents dimerization and phosphorylation of the activation loop of MST2 independently of its protein kinase activity. Depletion of MST2 from Raf-1-/- mouse or human cells abrogated sensitivity to apoptosis, whereas overexpression of MST2 induced apoptosis. Conversely, depletion of Raf-1 from Raf-1+/+ mouse or human cells led to MST2 activation and apoptosis. The concomitant depletion of both Raf-1 and MST2 prevented apoptosis.     

Quantitative imaging of lateral ErbB1 receptor signal propagation in the plasma membrane

Evidence for a new signaling mechanism consisting of ligand-independent lateral propagation of receptor activation in the plasma membrane is presented. We visualized the phosphorylation of green fluorescent protein (GFP)-tagged ErbB1 (ErbB1-GFP) receptors in cells focally stimulated with epidermal growth factor (EGF) covalently attached to beads. This was achieved by quantitative imaging of protein reaction states in cells by fluorescence resonance energy transfer (FRET) with global analysis of fluorescence lifetime imaging microscopy (FLIM) data. The rapid and extensive propagation of receptor phosphorylation over the entire cell after focal stimulation demonstrates a signaling wave at the plasma membrane resulting in full activation of all receptors.     

Identification of the envelope V3 loop as the primary determinant of cell tropism in HIV-1

Cells of the monocyte-macrophage lineage are targets for human immunodeficiency virus-1 (HIV-1) infection in vivo. However, many laboratory strains of HIV-1 that efficiently infect transformed T cell lines replicate poorly in macrophages. A 20-amino acid sequence from the macrophage-tropic BaL isolate of HIV-1 was sufficient to confer macrophage tropism on HTLV-IIIB, a T cell line--tropic isolate. This small sequence element is in the V3 loop, the envelope domain that is the principal neutralizing determinant of HIV-1. Thus, the V3 loop not only serves as a target of the host immune response but is also pivotal in determining HIV-1 tissue tropism.     

Mapping of the human Blym-1 transforming gene activated in Burkitt lymphomas to chromosome 1

Blym-1, a transforming gene detected by transfection of NIH 3T3 cells with DNA from Burkitt lymphomas, was mapped to the short arm of chromosome 1 (1p32) by chromosomal in situ hybridization. The Blym-1 gene was not physically linked to the cellular myc oncogene or to any of the immunoglobulin gene loci implicated in the characteristic chromosomal translocations in Burkitt lymphoma.     

Catastrophic drought in the Afro-Asian monsoon region during Heinrich event 1

Between 15,000 and 18,000 years ago, large amounts of ice and meltwater entered the North Atlantic during Heinrich stadial 1. This caused substantial regional cooling, but major climatic impacts also occurred in the tropics. Here, we demonstrate that the height of this stadial, about 16,000 to 17,000 years ago (Heinrich event 1), coincided with one of the most extreme and widespread megadroughts of the past 50,000 years or more in the Afro-Asian monsoon region, with potentially serious consequences for Paleolithic cultures. Late Quaternary tropical drying commonly is attributed to southward drift of the intertropical convergence zone, but the broad geographic range of the Heinrich event 1 megadrought suggests that severe, systemic weakening of Afro-Asian rainfall systems also occurred, probably in response to sea surface cooling.     

Color defect and color theory; studies of normal and colorblind persons,including a subject color-blind in one eye but not in the other

It is important to find answers to two questions concerning the visual discriminations of dichromatic persons, especially deuteranopes: (i) Do such persons show a loss of sensitivity to various wavelengths of the spectrum as compared with normal subjects? (ii) What colors do they see? A number of experiments were performed on the first question. First, luminosity curves were determined on three groups of subjects, consisting respectively of five protanopes, six deuteranopes, and seven normal individuals. As compared with normal subjects, protanopes show a loss of luminosity in the red, whereas deuteranopes show a loss in the blue-to-green region of the spectrum (See 10). Second, we examined the luminosity curves of a subject whose right eye is classifiable (on the basis of color-mixture determinations) as normal and whose left eye is classifiable as dichromatic. (The hue discrimination curve for her dichromatic eye seemed comparable to the curve of the usual deuteranope except in the violet, where it manifested relatively good discrimination.) The luminosity function for this subject's dichromatic eye, determined by data on threshold and flicker, exhibits the same type of luminosity loss in the blue and green regions of the spectrum as was shown by our group of six deuteranopes. Only unilaterally dichromatic subjects can tell us how colors seen by a dichromatic eye appear to a normal eye. In the color-blind eye, our unilaterally dichromatic subject sees wavelengths below and above her neutral ("grey") point (which occurs at 502 mmicro) as, respectively, a blue equivalent to about 470 mmicro and a yellow equivalent to about 570 mmicro in her normal eye. The results on (i) luminosity loss and (ii) the seeing of wavelengths above 502 mmicro as yellow are considered theoretically. The seeing of yellow by deuteranopes and protanopes may be accounted for by an idea based on Leber-Fick transmation theory. It is proposed that the characteristic sensitivities of the red and green receptors become similar while no change takes place in their central brain connections. Losses may be introduced into the transformed sensitivity curves to indicate appropriate degrees of luminosity deficit for deuteranopes and protanopes.