Herpesvirus saimiri episomal persistence is maintained via interaction between open reading frame 73 and the cellular chromosome-associated protein MeCP2

Herpesvirus saimiri (HVS) is the prototype gamma-2 herpesvirus, which naturally infects the squirrel monkey Saimiri sciureus, causing an asymptomatic but persistent infection. The latent phase of gamma-2 herpesviruses is characterized by their ability to persist in a dividing cell population while expressing a limited subset of latency-associated genes. In HVS only three genes, open reading frame 71 (ORF71), ORF72, and ORF73, are expressed from a polycistronic mRNA. ORF73 has been shown to be the only gene essential for HVS episomal maintenance and can therefore be functionally compared to the human gammaherpesvirus latency-associated proteins, EBNA-1 and Kaposi's sarcoma-associated herpesvirus (KSHV) latency-associated nuclear antigen (LANA). HVS ORF73 is the positional homologue of KSHV LANA and, although it shares limited sequence homology, has significant structural and functional similarities. Investigation of KSHV LANA has demonstrated that it is able to mediate KSHV episomal persistence by tethering the KSHV episome to host mitotic chromosomes via interactions with cellular chromosome-associated proteins. These include associations with core and linker histones, several bromodomain proteins, and the chromosome-associated proteins methyl CpG binding protein 2 (MeCP2) and DEK. Here we show that HVS ORF73 associates with MeCP2 via a 72-amino-acid domain within the ORF73 C terminus. Furthermore, we have assessed the functional significance of this interaction, using a variety of techniques including small hairpin RNA knockdown, and show that association between ORF73 and MeCP2 is essential for HVS chromosomal attachment and episomal persistence.     

Imbalance of the antioxidant network of mouse small intestinal mucosa after radiation exposure

The aim of this study was to investigate acute variations in antioxidant defense systems in the intestinal mucosa after abdominal radiation exposure and the role played by radiation-induced inflammation in these variations. Antioxidant defense systems of mouse small intestinal mucosa were studied at 6 h and 4 days after abdominal radiation exposure. Superoxide dismutases, glutathione peroxidases, catalase, metallothioneins and thioredoxins were followed in terms of mRNA expression, protein expression and enzyme activities. Dexamethasone was administered to investigate the relationship between variations in mucosal antioxidant capacity and radiation-induced inflammation. Six hours after exposure, only mitochondrial-associated antioxidant systems were induced (the superoxide dismutase and thioredoxin 2). Four days after exposure, during the inflammatory phase, superoxide dismutases were decreased and modulations of the second line of the antioxidant network were also observed: Catalase was decreased and glutathione peroxidases and metallothioneins were induced. Dexamethasone treatment modulated only glutathione peroxidase expression and did not influence either metallothionein or superoxide dismutase expression. Our findings provide direct in vivo evidence that antioxidant mechanisms of the small intestinal mucosa were not markedly mobilized during the very acute tissue radiation response. During the radiation-induced acute inflammatory response, the antioxidant capacity appeared to be dependent on inflammatory status to a certain extent.     

A <Emphasis Type="Italic">Pseudo-Response Regulator</Emphasis> is misexpressed in the photoperiod insensitive <Emphasis Type="Italic">Ppd-D1a</Emphasis> mutant of wheat (<Emphasis Type="Italic">Triticum aestivum</Emphasis> L.)

Ppd-D1 on chromosome 2D is the major photoperiod response locus in hexaploid wheat (Triticum aestivum). A semi-dominant mutation widely used in the “green revolution” converts wheat from a long day (LD) to a photoperiod insensitive (day neutral) plant, providing adaptation to a broad range of environments. Comparative mapping shows Ppd-D1 to be colinear with the Ppd-H1 gene of barley (Hordeum vulgare) which is a member of the pseudo-response regulator (PRR) gene family. To investigate the relationship between wheat and barley photoperiod genes we isolated homologues of Ppd-H1 from a ‘Chinese Spring’ wheat BAC library and compared them to sequences from other wheat varieties with known Ppd alleles. Varieties with the photoperiod insensitive Ppd-D1a allele which causes early flowering in short (SD) or LDs had a 2 kb deletion upstream of the coding region. This was associated with misexpression of the 2D PRR gene and expression of the key floral regulator FT in SDs, showing that photoperiod insensitivity is due to activation of a known photoperiod pathway irrespective of day length. Five Ppd-D1 alleles were found but only the 2 kb deletion was associated with photoperiod insensitivity. Photoperiod insensitivity can also be conferred by mutation at a homoeologous locus on chromosome 2B (Ppd-B1). No candidate mutation was found in the 2B PRR gene but polymorphism within the 2B PRR gene cosegregated with the Ppd-B1 locus in a doubled haploid population, suggesting that insensitivity on 2B is due to a mutation outside the sequenced region or to a closely linked gene. Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. J. Beales and A. Turner contributed equally to the work.     

Advances in the application of scanning electrochemical microscopy to bioanalytical systems

Scanning electrochemical microscopy (SECM) is a powerful surface characterisation technique that allows for the electrochemical profiling of surfaces with sub micrometer resolution. While SECM has been most widely used to electrochemically study and profile non-biological surfaces and processes, the technique has in recent years, been increasingly used for the study of biological systems - and this is the focus of this review. An overview of SECM and how the technique may be applied to the study of biological systems will first be given. SECM and its application to the study of cells, enzymes and DNA will each be considered in detail. The review will conclude with a discussion of future directions and scope for further developments and applications.     

Vitamin D in the treatment of pulmonary tuberculosis

Vitamin D was used to treat tuberculosis in the pre-antibiotic era. New insights into the immunomodulatory properties of 1alpha,25-dihydroxy-vitamin D have rekindled interest in vitamin D as an adjunct to antituberculous therapy. We describe the historical use of vitamin D in tuberculosis treatment; discuss the mechanisms by which it may modulate host response to infection with Mycobacterium tuberculosis; and review three clinical trials and ten case series in which vitamin D has been used in the treatment of pulmonary tuberculosis.     

Protein-tyrosine phosphatase sigma is associated with ulcerative colitis

Inflammatory bowel disease (IBD), a relatively common chronic debilitating intestinal illness, is composed of two broadly defined groups, Crohn's disease (CD) and ulcerative colitis (UC). Although several susceptibility genes for CD have been recently described, susceptibility genes exclusive for UC have not been forthcoming. Here, we show that receptor protein-tyrosine phosphatase sigma (PTPRS-encoding PTPsigma) knockout mice spontaneously develop mild colitis that becomes severe when challenged with two known inducers of colitis. We also demonstrate that E-cadherin and beta-catenin, two important adherens junction proteins involved in maintenance of barrier defense in the colon, act as colonic substrates for PTPsigma. Furthermore, we show that three SNPs (rs886936, rs17130, and rs8100586) that flank exon 8 in the human PTPRS gene are associated with UC. The presence of these SNPs is associated with novel splicing that removes the third immunoglobulin-like domain (exon 9) from the extracellular portion of PTPsigma, possibly altering dimerization or ligand recognition. We propose that polymorphisms in the human PTPRS gene lead to ulcerative colitis.