Attenuated signaling associated with immune activation in HIV-1-infected individuals

Chronic immune activation is associated with impaired signal transduction. Since such activation is commonly found during HIV-1 infection, we studied cellular responses to non-specific T-cell receptor stimulation of PBMC obtained from 20 HIV-1 non-infected individuals and 23 highly or partially immune activated HIV-1 infected individuals. PBMC proliferation and ERK-1/2 phosphorylation following anti-CD3 stimulation, and constitutive levels of Cbl-b, were determined. Increased levels of Cbl-b, decreased proliferation, and lower ERK-1/2 phosphorylation were found in PBMC of highly immune activated HIV-1 infected individuals. The elevated expression of Cbl-b and impaired phosphorylation of ERK-1/2 associated with immune activation probably contribute to the attenuated proliferative and cellular responses characteristic of HIV-1 infection. Therefore, targeting immune negative modulators, such as Cbl-b, may serve as a novel approach for controlling HIV-1 disease progression.     

Rad6p represses yeast-hypha morphogenesis in the human fungal pathogen Candida albicans

Rad6p plays important roles in post-replication DNA repair, chromatin organization, gene silencing and meiosis. In this study, we show that Rad6p also regulates yeast-hypha morphogenesis in the human pathogen Candida albicans. CaRAD6 gene and cDNAs were isolated and characterized revealing that the gene carries two 5'-proximal introns. CaRad6p shows a high degree of sequence similarity to Rad6 proteins from fungi to man (60-83% identity), and it suppresses the UV sensitivity and lack of induced mutagenesis displayed by a Saccharomyces cerevisiae rad6 mutant. In C. albicans, CaRAD6 expression is induced in response to UV, and CaRad6p depletion confers UV sensitivity, confirming that Rad6p serves a role in protecting this fungus against UV damage. CaRAD6 overexpression inhibits hyphal development, whereas CaRad6p depletion enhances hyphal growth. Also, CaRAD6 mRNA levels decrease during the yeast-hypha transition. These effects are dependent on Efg1p, but not Cph1p, indicating that CaRad6p acts specifically through the Efg1p morphogenetic signalling pathway to repress yeast-hypha morphogenesis.     

Residues 240–250 in the C-Terminus of the Pirh2 Protein Complement the Function of the RING Domain in Self-Ubiquitination of the Pirh2 Protein

Pirh2 is a p53 inducible gene that encodes a RING-H2 domain and is proposed to be a main regulator of p53 protein, thus fine tuning the DNA damage response. Pirh2 interacts physically with p53 and promotes its MDM2-independent ubiquitination and subsequent degradation as well as participates in an auto-regulatory feedback loop that controls p53 function. Pirh2 also self-ubiquitinates. Interestingly, Pirh2 is overexpressed in a wide range of human tumors. In this study, we investigated the domains and residues essential for Pirh2 self-ubiquitination. Deletions were made in each of the three major domains of Pirh2: the N-terminal domain (NTD), Ring domain (RING), and C-terminal domain (CTD). The effects of these deletions on Pirh2 self-ubiquitination were then assessed using in vitro ubiquitination assays. Our results demonstrate that the RING domain is essential, but not sufficient, for Pirh2 self-ubiquitination and that residues 240–250 of the C-terminal domain are also essential. Our results demonstrate that Pirh2 mediated p53 polyubiquitination occurs mainly through the K48 residue of ubiquitin in vitro. Our data further our understanding of the mechanism of Pirh2 self-ubiquitination and may help identify valuable therapeutic targets that play roles in reducing the effects of the overexpression of Pirh2, thus maximizing p53''s response to DNA damage.     

DSP1, an HMG-like protein, is involved in the regulation of homeotic genes

The Drosophila dsp1 gene, which encodes an HMG-like protein, was originally identified in a screen for corepressors of Dorsal. Here we report that loss of dsp1 function causes homeotic transformations resembling those associated with loss of function in the homeotic genes Sex combs reduced (Scr), Ultrabithorax (Ubx), and Abdominal-B. The expression pattern of Scr is altered in dsp1 mutant imaginal discs, indicating that dsp1 is required for normal expression of this gene. Genetic interaction studies reveal that a null allele of dsp1 enhances trithorax-group gene (trx-G) mutations and partially suppresses Polycomb-group gene (Pc-G) mutations. On the contrary, overexpression of dsp1 induces an enhancement of the transformation of wings into halteres and of the extra sex comb phenotype of Pc. In addition, dsp1 male mutants exhibit a mild transformation of A4 into A5. Comparison of the chromatin structure at the Mcp locus in wild-type and dsp1 mutant embryos reveals that the 300-bp DNase I hypersensitive region is absent in a dsp1 mutant context. We propose that DSP1 protein is a chromatin remodeling factor, acting as a trx-G or a Pc-G protein depending on the considered function.     

Characterisation of the complete mitochondrial genome of the black-footed abalone Haliotis iris

The complete mitogenome of Haliotis iris, an economically important shellfish endemic to New Zealand, was sequenced for the first time. The mitogenome was 17,131?base pairs (bp) in length and contained 13 protein-coding genes (PCGs), 2 ribosomal RNA (rRNA) genes, 22 transfer RNA (tRNA) genes and a control region. All 13 genes were initiated by the start codon ATG, except for nad5 (ATA). Two typical stop codons, TAA and TAG, were present. All of the tRNAs could be folded into typical cloverleaf secondary structures except tRNA^Ser1 and tRNA^Lys, which lacked a DHU stem and complete amino acid acceptor stem, respectively. The control region was 1132?bp in length and contained six AT tandem repeats. According to the gene order of the mitogenome, the 30 analysed Vetigastropoda species could be classified into three types—type I: over half of the studied species were very similar to the gastropod ancestral gene order, and the rearrangements occurred in five tRNAs; type II: eight species were found to be missing several tRNA genes; type III: Fissurellidae, Lepetodrilidae showed a large inverted fragment.     

Conformational changes induced in DNA by the in vitro reaction with the mutagenic amine: 3-N,N-acetoxyacetylamino-4,6-dimethyldipyrido (1,2-a: 3', 2'-d) imidazole.

The conformation of synthetic or natural DNAs modified in vitro by covalent binding of N-AcO-A-Glu-P-3 was investigated by fluorescence and circular dichroism. In all cases, substitution occurs mainly on the C8 of guanine residues. In modified poly(dG-dC).poly(dG-dC) or poly(dA-dC).poly(dG-dT) in B conformation, A-Glu-P-3 residues interact strongly with the bases whereas in Z conformation these residues are largely exposed to the solvent and interact weakly with the bases. A-Glu-P-3 and N-acetyl-2-aminofluorene (AAF) residues are equally efficient to induce the B-Z transition of poly(dG-dC).poly(dG-dC) and of poly(dA-dC).poly(dG-dT). Modifications of poly(dG).poly(dC) and calf thymus DNA indicate strong interactions between A-Glu-P-3 and the bases.     

Reaction of nucleic acids with cis-diamminedichloroplatinum(II): interstrand cross-links

In the reaction of cis-diamminedichloroplatinum(II) (cis-DDP) with double-helical (dC-dG)4.(dC-dG)4 or (dC-dG)5.(dC-dG)5, intrastrand and interstrand cross-links between two guanine residues are formed. This is shown by gel electrophoresis in denaturing conditions of the reaction products and by high-performance liquid chromatography (HPLC) analysis of the products digested with nuclease P1. In the reaction of cis-DDP and poly(dG-dC).poly(dG-dC), at relatively low levels of platination, it is mainly interstrand cross-links between two guanine residues that are formed. This is shown by HPLC analysis of the nuclease P1 digest and by gel electrophoresis in denaturing and nondenaturing conditions of the platinated polymer after cleavage with the restriction enzyme HhaI. Moreover, the antibodies to platinated poly(dG-dC).poly(dG-dC) cross-react with the interstrand cross-linked (dC-dG)4 or (dC-dG)5 but not with the intrastrand cross-linked (dC-dG)4 or (dC-dG)5. These antibodies cross-react with platinated natural DNA. The amount of interstrand cross-links deduced from radioimmunoassays (0.5% of the total bound platinum) is lower than that (2%) deduced by gel electrophoresis in denaturing conditions of a platinated DNA restriction fragment. By gel electrophoresis, it is also shown that in vitro the isomer trans-DDP is more efficient in forming interstrand cross-links than cis-DDP.     

Thermal stability of the Z-conformation of the tetranucleoside triphosphate (m5dC-dG)2

The tetranucleoside triphosphate d(m5C-G)2 has been studied in solution by circular dichroism and 31P nuclear magnetic resonance as a function of temperature, in presence of 3 M NaClO4. It is shown that in such high ionic strength d(m5C-G)2 may adopt a Z-like conformation for temperatures lower than 5 degrees C. At these temperatures, another conformation, in slow equilibrium with the Z-like one, is also detected. Increasing the temperature leads to a transition from the Z-like conformation to intermediate forms before melting. It is demonstrated that these intermediates are not the B form.     

四川阿坝州大花红景天的生境调查与植物群落特点

为研究四川阿坝州野生大花红景天的生态环境及其分布,解决其种质资源的有效保护和可持续利用问题,采用野外样方调查方法,对大花红景天资源的分布和生境及其植物群落特点进行了调查研究.通过调查发现,大花红景天适宜在阿坝州地区生长,土壤主要为亚高山草甸土和高山草甸土.在亚高山草甸区的植物群落特点主要为:禾本草+嵩草+杂类草型,高山草甸区主要以莎草和垫状杂草构成,草群低矮,平均高度22 cm,植物盖度不及45%.