青霉菌组蛋白去乙酰化酶基因的敲除及其次级代谢产物变化

丝状真菌尤其是青霉菌Penicillium代谢的各类次级产物日趋成为研制新药的重要来源,很多药物如抗癌药物、抗生素、免疫抑制剂等均来源于真菌。然而真菌次级代谢受多因素的影响,其中表观遗传修饰起到重要的调控作用。组蛋白乙酰化表观遗传修饰常与转录激活相关,从而促进次级代谢产物的合成。以青霉属真菌Penicillium christenseniae SD-193.84为研究对象,利用生物信息学手段确定其组蛋白去乙酰化酶（HDAC）基因,建立该菌中同源重组基因敲除技术,对该基因进行敲除,并比较了基因敲除前后次级代谢产物的变化,发现HDAC影响了多种次级代谢产物的合成。本研究为青霉菌分子遗传操作及次级代谢调控提供了参考。     

Structures of a histone deacetylase homologue bound to the TSA and SAHA inhibitors.

Histone deacetylases (HDACs) mediate changes in nucleosome conformation and are important in the regulation of gene expression. HDACs are involved in cell-cycle progression and differentiation, and their deregulation is associated with several cancers. HDAC inhibitors, such as trichostatin A (TSA) and suberoylanilide hydroxamic acid (SAHA), have anti-tumour effects, as they can inhibit cell growth, induce terminal differentiation and prevent the formation of tumours in mice models, and they are effective in the treatment of promyelocytic leukemia. Here we describe the structure of the histone deacetylase catalytic core, as revealed by the crystal structure of a homologue from the hyperthermophilic bacterium Aquifex aeolicus, that shares 35.2% identity with human HDAC1 over 375 residues, deacetylates histones in vitro and is inhibited by TSA and SAHA. The deacetylase, deacetylase-TSA and deacetylase-SAHA structures reveal an active site consisting of a tubular pocket, a zinc-binding site and two Asp-His charge-relay systems, and establish the mechanism of HDAC inhibition. The residues that make up the active site and contact the inhibitors are conserved across the HDAC family. These structures also suggest a mechanism for the deacetylation reaction and provide a framework for the further development of HDAC inhibitors as antitumour agents.     

The roles of intracellular protein-degradation pathways in neurodegeneration

Many late-onset neurodegenerative diseases, including Parkinson's disease and Huntington's disease, are associated with the formation of intracellular aggregates by toxic proteins. It is therefore crucial to understand the factors that regulate the steady-state levels of these 'toxins', at both the synthetic and degradation stages. The degradation pathways acting on such aggregate-prone cytosolic proteins include the ubiquitin-proteasome system and macroautophagy. Dysfunction of the ubiquitin-proteasome or macroautophagy pathways might contribute to the pathology of various neurodegenerative conditions. However, enhancing macroautophagy with drugs such as rapamycin could offer a tractable therapeutic strategy for a number of these diseases.     

The identification and suppression of inherited neurodegeneration in Caenorhabditis elegans

The dominant mutation deg-1(u38) results in a toxic gene product that leads to the late-onset degeneration of a small number of neurons in the nematode Caenorhabditis elegans. Both intragenic and extragenic mutations as well as changes in wild-type gene dosage can delay or block the time of onset of the neuronal deaths. The deg-1 gene has been cloned and a partial complementary DNA reveals that the gene encodes a novel protein that may act as a membrane receptor. Because the late-onset loss of specific sets of neurons, often as a result of dominant mutations, is characteristic of several human neurodegenerative diseases, the analysis of the deg-1 gene and its suppressors may provide a means of understanding the mechanisms underlying some of these human diseases.     

Wolbachia在Drosophila auraria复合种和Drosophila simulans中的感染

用 Ｐ Ｃ Ｒ 方法检测了多种果蝇中共生菌 Ｗ ｏｌｂａｃｈｉａ 的感染,发现 Ｄｒｏｓｏｐｈｉｌａ ａｕｒａｒｉａ 复合种以及采集于北京地区的 Ｄｒｏｓｏｐｈｉｌａ ｓｉｍ ｕｌａｎｓ为 Ｗｏｌｂａｃｈｉａ 所感染, Ｒ Ｆ Ｌ Ｐ分析证实为单一感染．克隆了编码 Ｗ ｏｌｂａｃｈｉａ 外膜蛋白质的 ｗ ｓｐ 基因并进行了序列测定．同时比较了 Ｄｒｏｓｏｐｈｉｌａ ａｕｒａｒｉａ 复合种内 ４ 个种和采集于北京及美国加州的 Ｄｒｏｓｏｐｈｉｌａ ｓｉｍ ｕｌａｎｓ 的线粒体的细胞色素氧化酶 ２ 亚基基因的部分序列． 进而讨论了 Ｗｏｌｂａｃｈｉａ 对 Ｄｒｏｓｏｐｈｉｌａ ａｕｒａｒｉａ 复合种成员之间进化关系的影响．     

Loss of autophagy in the central nervous system causes neurodegeneration in mice

Protein quality-control, especially the removal of proteins with aberrant structures, has an important role in maintaining the homeostasis of non-dividing neural cells. In addition to the ubiquitin-proteasome system, emerging evidence points to the importance of autophagy--the bulk protein degradation pathway involved in starvation-induced and constitutive protein turnover--in the protein quality-control process. However, little is known about the precise roles of autophagy in neurons. Here we report that loss of Atg7 (autophagy-related 7), a gene essential for autophagy, leads to neurodegeneration. We found that mice lacking Atg7 specifically in the central nervous system showed behavioural defects, including abnormal limb-clasping reflexes and a reduction in coordinated movement, and died within 28 weeks of birth. Atg7 deficiency caused massive neuronal loss in the cerebral and cerebellar cortices. Notably, polyubiquitinated proteins accumulated in autophagy-deficient neurons as inclusion bodies, which increased in size and number with ageing. There was, however, no obvious alteration in proteasome function. Our results indicate that autophagy is essential for the survival of neural cells, and that impairment of autophagy is implicated in the pathogenesis of neurodegenerative disorders involving ubiquitin-containing inclusion bodies.     

Visual transduction in Drosophila

The brain's capacity to analyse and interpret information is limited ultimately by the input it receives. This sets a premium on information capacity of sensory receptors, which can be maximized by optimizing sensitivity, speed and reliability of response. Nowhere is selection pressure for information capacity stronger than in the visual system, where speed and sensitivity can mean the difference between life and death. Phototransduction in flies represents the fastest G-protein-signalling cascade known. Analysis in Drosophila has revealed many of the underlying molecular strategies, leading to the discovery and characterization of signalling molecules of widespread importance.     

Histone arginine methylation regulates pluripotency in the early mouse embryo

It has been generally accepted that the mammalian embryo starts its development with all cells identical, and only when inside and outside cells form do differences between cells first emerge. However, recent findings show that cells in the mouse embryo can differ in their developmental fate and potency as early as the four-cell stage. These differences depend on the orientation and order of the cleavage divisions that generated them. Because epigenetic marks are suggested to be involved in sustaining pluripotency, we considered that such developmental properties might be achieved through epigenetic mechanisms. Here we show that modification of histone H3, through the methylation of specific arginine residues, is correlated with cell fate and potency. Levels of H3 methylation at specific arginine residues are maximal in four-cell blastomeres that will contribute to the inner cell mass (ICM) and polar trophectoderm and undertake full development when combined together in chimaeras. Arginine methylation of H3 is minimal in cells whose progeny contributes more to the mural trophectoderm and that show compromised development when combined in chimaeras. This suggests that higher levels of H3 arginine methylation predispose blastomeres to contribute to the pluripotent cells of the ICM. We confirm this prediction by overexpressing the H3-specific arginine methyltransferase CARM1 in individual blastomeres and show that this directs their progeny to the ICM and results in a dramatic upregulation of Nanog and Sox2. Thus, our results identify specific histone modifications as the earliest known epigenetic marker contributing to development of ICM and show that manipulation of epigenetic information influences cell fate determination.     

Role of the prolyl isomerase Pin1 in protecting against age-dependent neurodegeneration

The neuropathological hallmarks of Alzheimer's disease and other tauopathies include senile plaques and/or neurofibrillary tangles. Although mouse models have been created by overexpressing specific proteins including beta-amyloid precursor protein, presenilin and tau, no model has been generated by gene knockout. Phosphorylation of tau and other proteins on serine or threonine residues preceding proline seems to precede tangle formation and neurodegeneration in Alzheimer's disease. Notably, these phospho(Ser/Thr)-Pro motifs exist in two distinct conformations, whose conversion in some proteins is catalysed by the Pin1 prolyl isomerase. Pin1 activity can directly restore the conformation and function of phosphorylated tau or it can do so indirectly by promoting its dephosphorylation, which suggests that Pin1 is involved in neurodegeneration; however, genetic evidence is lacking. Here we show that Pin1 expression is inversely correlated with predicted neuronal vulnerability and actual neurofibrillary degeneration in Alzheimer's disease. Pin1 knockout in mice causes progressive age-dependent neuropathy characterized by motor and behavioural deficits, tau hyperphosphorylation, tau filament formation and neuronal degeneration. Thus, Pin1 is pivotal in protecting against age-dependent neurodegeneration, providing insight into the pathogenesis and treatment of Alzheimer's disease and other tauopathies.