Polycomb group蛋白复合体

Polycomb group (PcG) 蛋白是一组通过染色质修饰调控靶基因的转录抑制子, 从生化和功能上它可以分成两个主要的核心蛋白复合体PRC1(Polycomb repressive complex 1)和PRC2(Polycomb repressive complex 2)。研究发现PcG蛋白不仅控制个体正确的发育模式, 而且与细胞的增殖、分化和肿瘤发生有关。文章就PcG蛋白的组成、作用机制及功能进行综述, 并对PcG未来的研究方向进行展望。     

Neighboring group stabilization by σ-holes

We have used density-functional theory to investigate the neighboring-group stabilization of iodine, arsenic, and phosphorus-centered oxyanion moieties in species such as deprotonated 2-iodoxybenzoic acid (IBX) and its analogs. The magnitudes of different stabilizing effects and further candidates for analogous stabilization are analyzed.      

Should you form a group?

In this discussion, greatest emphasis has been placed upon the personal factors involved, rather than upon the mechanical aspects of creating and maintaining a group, since it is the personal factors, the authors say, that are the most often overlooked.     

Phosphatocopina – ostracode-like sister group of Eucrustacea

The Phosphatocopina were long considered as the oldest, Cambrian, record of ostracode Crustacea. However, our detailed analysis of more than 2,500 specimens from the Upper Cambrian ‘Orsten’ of Sweden reveals that Phosphatocopina are neither Ostracoda nor Eucrustacea. The antenna and mandible of the phosphatocopines investigated consist of a prominent limb stem which carries a two-segmented endopod and multi-annulated exopod. This stem portion is now recognised as the fusion product of the coxa and basipod during ontogeny. Phosphatocopina share features, such as the coxa and basipod on antennae and mandibles, as well as ventral body structures such as the prominent pre-oral labrum and a single post-oral cephalic plate, the sternum (with paragnaths on the mandibular sternal portion), exclusively with the Eucrustacea. As a plesiomorphy, the ontogeny of Phosphatocopina starts with a ‘head larva’ with four pairs of limbs, a larva type found in the ground pattern of the Euarthropoda as well as the Crustacea. In contrast, eucrustacean ontogeny begins with a nauplius with three pairs of limbs, a ‘short-head larva’ or orthonauplius. Again, the post-mandibular limbs of phosphatocopines retain the plesiomorphic limb design of a basipod with a setiferous ‘ proximal endite’, whereas Eucrustacea, including the Ostracoda, have their first post-mandibular limb differentiated into a ‘ mouthpart’, the maxillula. Autapomorphies of Phosphatocopina include the small antennula with few terminal setae, a bivalved shield with interdorsum, and the fused coxa and basipod on antenna and mandible. We therefore consider the Phosphatocopina to be the sister group of the Eucrustacea. The respective phosphatocopine species of the Upper Cambrian of southern Sweden are restricted to a particular time zone and may be useful as stratigraphic markers.     

Does information sharing promote group foraging?

Individuals may join groups for several reasons, one of which is the possibility of sharing information about the quality of a foraging area. Sharing information in a patch-foraging scenario gives each group member an opportunity to make a more accurate estimate of the quality of the patch. In this paper we present a mathematical model in which we study the effect of group size on patch-leaving policy and per capita intake rate. In the model, group members share information equally in a random search for food. Food is distributed in patches according to a negative binomial distribution. A prediction from our model is that, the larger the group, the earlier each group member should leave the current patch. We also find that the benefit from enhanced exchange of information does not exceed the cost of sharing food with group members. The per capita intake rate decreases as the group size increases. Therefore, animals should only form groups when other factors outweigh the costs, which is easiest to achieve when the travelling time is short.     

Experimental studies of group selection: what do they tell us about group selection in nature?

The study of group selection has developed along two autonomous lines. One approach, which we refer to as the adaptationist school, seeks to understand the evolution of existing traits by examining plausible mechanisms for their evolution and persistence. The other approach, which we refer to as the genetic school, seeks to examine how currently acting artificial or natural selection changes traits within populations and focuses on current evolutionary change. The levels of selection debate lies mainly within the adaptationist school, whereas the experimental studies of group selection lie within the genetic school. Because of the very different traditions and goals of these two schools, the experimental studies of group selection have not had a major impact on the group selection debate. We review the experimental results of the genetic school in the context of the group selection controversy and address the following questions: Under what conditions is group selection effective? What is the genetic basis of a response to group selection? How common is group selection in nature?     

adjuvant chemotherapy group, 56 patients received a

1%,26.6% and 27.7% respectively.there was no significant discrepancy(P>0.05).The 5-year survival in 3 or 4 cycles patients were 26.7% and the 5-year survival in 5 or 6 cycles patients were 28.9% .there was no significant discrepancy(P>0.05).Conclusion:Postoperative adjuvant chemotherapy with platinum-based regimen for 3 or 4 cycles can improve survival rate for stage Ⅲ NSCLC patients.Non-small-cell lung cancer; Surgery; Adjuvant chemotherapy; Survival rate0临床肿瘤学杂志Chinese Clinical Oncology19-21R734.2E0724E;E072_4潘泓;173-175长春瑞滨联合卡铂治疗老年晚期非小细胞肺癌胡兴胜;张湘茹;储大同; 中国医学科学院     

Are polycomb group bodies gene silencing factories?

Polycomb group (PcG) proteins mediate long-range associations between Hox genes, which correlate with gene repression in vivo. Bantignies et al. (2011) identify a physiological role for the nuclear localization of Hox genes in PcG-mediated gene silencing, strengthening the evidence that nuclear positioning regulates gene expression.     

Do glial cells control pain?

Management of chronic pain is a real challenge, and current treatments that focus on blocking neurotransmission in the pain pathway have resulted in limited success. Activation of glial cells has been widely implicated in neuroinflammation in the CNS, leading to neurodegeneration in conditions such as Alzheimer's disease and multiple sclerosis. The inflammatory mediators released by activated glial cells, such as tumor necrosis factor-a and interleukin-1b not only cause neurodegeneration in these disease conditions, but also cause abnormal pain by acting on spinal cord dorsal horn neurons in injury conditions. Pain can also be potentiated by growth factors such as brain-derived growth factor and basic fibroblast growth factor, which are produced by glia to protect neurons. Thus, glial cells can powerfully control pain when they are activated to produce various pain mediators. We review accumulating evidence that supports an important role for microglial cells in the spinal cord for pain control under injury conditions (e.g. nerve injury). We also discuss possible signaling mechanisms, in particular mitogen-activated protein kinase pathways that are crucial for glial-mediated control of pain.Investigating signaling mechanisms in microglia might lead to more effective management of devastating chronic pain.     

Can fungal biopesticides control malaria?

Recent research has raised the prospect of using insect fungal pathogens for the control of vector-borne diseases such as malaria. In the past, microbial control of insect pests in both medical and agricultural sectors has generally had limited success. We propose that it might now be possible to produce a cheap, safe and green tool for the control of malaria, which, in contrast to most chemical insecticides, will not eventually be rendered useless by evolution of resistance. Realizing this potential will require lateral thinking by biologists, technologists and development agencies.     

Headcase gene--proliferation or hormonal control?

A new insertion allele of the hdc gene was isolated and described. The nucleotide sequence of the coding region had no detectable homology with genomic DNA of any other Drosophila species, except for D. mauritiana. Gene expression was found both in adult testes and ovaries and at embryonic and larval stages. This expression pattern exhibits a strong similarity to that of cell-cycle genes. In contrast to cycE (a typical cell-cycle gene), which leads to expression termination after in vivo culturing of the wing disk, hdc did not arrest expression. It is concluded that hdc is a species-specific differentiation gene, whose regulatory activity in the development of an organism differs from that of proliferation genes.     

A 3-hydroxy β-end group in xanthophylls is preferentially oxidized to a 3-oxo ε-end group in mammals

We previously found that mice fed lutein accumulated its oxidative metabolites (3′-hydroxy-ε,ε-caroten-3-one and ε,ε-carotene-3,3′-dione) as major carotenoids, suggesting that mammals can convert xanthophylls to keto-carotenoids by the oxidation of hydroxyl groups. Here we elucidated the metabolic activities of mouse liver for several xanthophylls. When lutein was incubated with liver postmitochondrial fraction in the presence of NAD⁺, (3′R,6′R)-3′-hydroxy-β,ε-caroten-3-one and (6RS,3′R,6′R)-3′-hydroxy-ε,ε-caroten-3-one were produced as major oxidation products. The former accumulated only at the early stage and was assumed to be an intermediate, followed by isomerization to the latter. The configuration at the C3′ and C6′ of the ε-end group in lutein was retained in the two oxidation products. These results indicate that the 3-hydroxy β-end group in lutein was preferentially oxidized to a 3-oxo ε-end group via a 3-oxo β-end group. Other xanthophylls such as β-cryptoxanthin and zeaxanthin, which have a 3-hydroxy β-end group, were also oxidized in the same manner as lutein. These keto-carotenoids, derived from dietary xanthophylls, were confirmed to be present in plasma of normal human subjects, and β,ε-caroten-3′-one was significantly increased by the ingestion of β-cryptoxanthin. Thus, humans as well as mice have oxidative activity to convert the 3-hydroxy β-end group of xanthophylls to a 3-oxo ε-end group.     

Cancer-retina antigens — A new group of tumor antigens

Some photoreceptor proteins normally specific for the eye retina are aberrantly expressed in malignant tumors. These proteins include recoverin, visual rhodopsin, transducin, cGMP-phosphodiesterase 6 (PDE 6), cGMP-dependent cationic channels, guanylyl cyclase 1, rhodopsin kinase, and arrestin. By analogy with cancer-testis antigens, these photoreceptor proteins form the group of cancer-retina antigens. It is shown that an aberrant demethylation of the promoter region of recoverin is involved in the aberrant expression of this protein. The cascade Wnt5a → Frizzled-2 → transducin → PDE 6 is shown to function in skin melanoma cells, and this suggests that these cancer-retina antigens can play a functional role. The events accompanying the signal transduction in this cascade, including those involving calcium ions and cGMP-dependent protein kinase (protein kinase G), are discussed.     

Within‐ and across‐group dating in Hawaii

Abstract

224 subjects from 5 different racial/ethnic groups responded to a dating questionnaire. There are both sex and racial/ethnic differences in frequency of cross‐ethnic dating in Hawaii and in attitudes (as reported by Ss) of parents and close friends toward within‐and across‐ethnic dating. Females date within their own groups more frequently than males and also report stronger support of within‐ and lesser support of across‐group dating by significant others. Racial/ethnic differences are substantial, with groups higher in mean income being more supportive of within‐group dating, being more accepted by other groups, and being less accepting of dating other groups. Amount of actual intergroup dating was related, in part, to group differences in income, with the two groups lowest in income (Filipinos and Hawaiians/Part Hawaiians) showing the highest amount of cross‐ethnic dating, but with the association breaking down in the upper income groups, possibly because of group differences in group size and in length of residence. The results are remarkably similar to those reported earlier on within‐ and across‐group marriage in Hawaii.