Topic: Involvement of X-box binding protein 1 and nucleophosmin in cellular and viral transcription
Speaker: Dr. Jimmy Chao Sheng Hao
Date: Tuesday, 12 August 2008 @ 11:00AM

Affiliation: Research Scientist, Expression Engineering II, Bioprocessing Technology Institute, Singapore

Convenor: Dr. Kevin Tan Shyong Wei

Abstract:
Many cellular factors are involved in host-virus interaction and required for viral transcription. In this seminar, I will present our recent findings regarding the involvement of two cellular proteins, X-box binding protein 1 (XBP-1) and nucleophosmin (NPM), in cellular and viral transcription.

Firstly, XBP-1, a basic leucine zipper protein, was found to bind to the long terminal repeat of human T-lymphotropic virus type 1 (HTLV-1) and activate HTLV-1 transcription through the interaction with a viral transactivator, Tax. Furthermore, elevated XBP-1 mRNA levels were detected in the HTLV-1-infected cell lines and Tax was identified as a positive regulator of the gene for XBP-1. Collectively, our results suggest a novel host-virus interaction between XBP-1 and HTLV-1.

Secondly, a nucleolar protein, NPM, was identified as a hexamethylene bis-acetamide-inducible protein 1 (HEXIM1) binding protein. HEXIM1 functions as an inhibitor of positive transcription elongation factor b (P-TEFb), which controls elongation phase of RNA polymerase II (Pol II) transcription. Overexpression of NPM leads to activation of P-TEFb-dependent transcription, including human immunodeficiency virus (HIV) Tat and HTLV-1 Tax transactivation.

We also show that a cytoplasmic mutant of NPM, NPMc+, associates with and sequesters HEXIM1 in the cytoplasm resulting in higher RNA Pol II transcription. Considering that 35% of acute myeloid leukemia (AML) patients are diagnosed with NPMc+ mutation, our findings suggest that in some cases of AML, RNA Pol II transcription may be disregulated by the malfunction of NPM and the mislocation of HEXIM1.

Topic: Novel cytokines in infectious and inflammatory disease
Speaker: Prof. Eddy Liew
Date: Monday, 18 August 2008 @ 11:00AM 

Affiliation: Glasgow Biomedical Research Centre, University of Glasgow, Glasgow, G12 8TA, UK

Convenor: Assoc. Prof. Herbert Schwarz

Abstract:
Cytokines are the hormones of the immune system and play a pivotal role in the induction and regulation of immune response. Cytokine targeting is arguably the most important contribution of immunology to clinical practice. Thus there is a considerable interest in the search for novel cytokines. The latest members of the cytokine family are IL-33 and IL-35.

IL-33, a member of the IL-1 family, is the newly discovered ligand for the orphan receptor ST2 which is expressed on a subset of Th2 cells (but not on Th1 cells) and mast cells. IL-33 is also able to skew a predominantly Th1 cell population to a mainly Th2 cells phenotype in vivo. IL-33 could attenuate an on going atherosclerosis in ApE mice on high fat diet. The disease attenuation was accompanied by the elevation of IL-5 and IL-6 production and the reduction of IFNγ synthesis in vitro and in vivo. Furthermore, the IL-33-treated mice produced increased level of anti-oxLDL antibody which is known to be protective against atherosclerosis. The effect of IL-33 on atherosclerosis was reversed by the co-treatment of the mice with sST2 (a decoy receptor of IL-33) and anti-IL-5 antibody. Hence it appears that IL-33 may be a potential therapeutic agent against atherosclerosis via the induction of IL-5 produced by Th2 cells and consequently enhances the production of anti-oxLDL antibody by B cells. However, IL-33 is a double-edged sword. It can also enhance allergic reaction and inflammatory disease such as arthritis and asthma.

IL-33 is expressed in synovial fibroblasts from patients with rheumatoid arthritis (RA). Expression is markedly elevated in vitro by inflammatory cytokines such as IL-1 and TNFα. Mice lacking ST2 developed attenuated collagen-induced arthritis (CIA) and reduced ex vivo collagen-specific induction of and proinflammatory antibody production. cytokines (IL-17, TNFα and IFNγ) of wild type (WT) but notConversely, treatment ST2 mice with IL-33 exacerbated CIA and elevated proinflammatory cytokine and anti-collagen antibody production. Mast cells express high levels of ST2 and responded directly to IL-33 to produce a spectrum of inflammatory cytokine and chemokines in vitro. In vivo, IL-33 treatment exacerbated CIA in ST2 mice engrafted with mast cells from WT but not from ST2 mice. The disease exacerbation was accompanied by elevated levels of proinflammatory cytokine expression. Thus IL-33 is a critical pro-inflammatory cytokine for inflammatory joint disease.

ST2 mice also developed attenuated airway inflammation and IL-5 production in a murine model of asthma. Conversely, IL 33 administration induced the IL 5-producing T cells and exacerbated allergen-induced airway inflammation in wild-type as well as IL 4 mice. Thus, in the presence of antigen, IL 33 induces IL 5 producing T cells and promotes airway inflammation independent of IL-4.

IL-33 mRNA is expressed early during parasite infection of the intestinal-dwelling nematode Trichuris muris in mice. Susceptible BALB/c mice can be induced by IL-33 to expel the parasite. Thus IL-33 may be evolutionally preserved for the host defence against intestinal parasitic infection.

IL-35 is the latest cytokine of the IL-12 family. It is formed by pairing Epstein-Barr virus-induced gene 3 (EBI3) and the p35 subunit of IL-12. The Fc fusion protein of IL-35 induced proliferation of murine CD4+CD25+ and CD4+CD25- T cells when stimulated with immobilized anti-CD3 and anti-CD28 antibodies in vitro. The IL-35-expanded CD4+CD25+ T cell population expressed Foxp3 and produced elevated levels of IL-10, whereas the IL-35-induced CD4+CD25- T cells produced IFNγ but not IL-4. The in vitro-expanded CD4+CD25+ T cells retained their suppressive functions against CD4+CD25- effector cells. Furthermore, when cultured with soluble anti-CD3 and antigen-presenting cells, IL-35 suppressed the proliferation of CD4+CD25- effector cells. Moreover, IL-35 inhibited the differentiation of Th17 cells in vitro. In vivo, IL-35 effectively attenuated established CIA in mice with concomitant suppression of IL-17 production but enhanced IFNγ synthesis. Thus IL-35 is a novel anti-inflammatory cytokine suppressing the immune response through the expansion of regulatory T cells and suppression of Th17 cell development.

Topic: Techniques with Focused Laser Beam: Optical Tweezers and their Potential Applications to Biological Samples?
Speaker: Assoc. Prof. Chorn Haur Sow
Date: Tuesday, 26 August 2008 @ 11:00AM

Affiliation: Department of Physics, National University of Singapore

Convenor: Dr Kevin Tan Shyong Wei

Abstract:
Laser traps or laser tweezers, also commonly known as optical traps or optical tweezers, are finding increasingly widespread applications in the study of mechanical deformation of isolated biological cells. In this method a laser beam, which is focused through a microscope objective lens, attracts and traps a high refractive index particle, and deformation is induced as the particle attached to a cell moves with the beam. The range of forces that can be imposed by the optical trap is typically on the order of tens-to-hundred of pico-Newton (pN = 10-12 N). Many important phenomena in biology, such as cell deformation, can be investigated using the optical tweezers. In this presentation, we hope to introduce the basic principles behind the optical tweezers and discuss some of the practical issues of setting up laser tweezers. We will also discuss some of the variations in experimental setups to achieve multiple-spots tweezers, line tweezers and optical tweezers in microfluidic device.

Topic: Characterising of Helicobacter pylori biofilm as a survival strategy in the extragastric environment
Speaker: Miss Ng Chow Goon
Date: Wednesday, 16 July 2008 @ 3:00PM

Affiliation: MSc Candidate, Department of Microbiology, NUS

Convenor: Assoc. Prof. Ho Bow

Topic: “Hokoviruses” and the discovery of other novel pathogens in HK
Speaker: Dr. Herman Tse
Date: Friday, 25 July 2008 @ 11:00AM

Affiliation: Department of Microbiology, The University of Hong Kong, Hong Kong

Convenor: Dr. Kevin Tan Shyong Wei

Abstract:
The dangers presented by previously unknown viruses had been exemplified by the SARS outbreak. Active surveillance is one important component in the defense against these dangers. My colleagues and I have been screening different clinical and animal specimens, with several new human and animal viruses identified. “Hokovirus” is the designation for a group of novel viruses most recently identified in our laboratory. The novel viruses are phylogenetically related to the newly discovered human parvoviruses PARV4 and PARV5. Their epidemiological and genomic features will be discussed, and the story of the serendipitous discovery will also be touched upon.

Topic: Chronic enteroviral infections in the post-polio syndrome and type-1 diabetes mellitus
Speaker: Prof. Antonio Toniolo, MD
Date: Wednesday, 30 July 2008 @ 4:00PM

Affiliation: University of Insubria Medical School, Varese, Italy

Convenor: Dr. Kevin Tan Shyong Wei

Abstract:
Polioviruses (PVs) belong to the human Enterovirus (HEV) group of Picornaviridae and are the etiologic agents of paralytic poliomyelitis. Decades after being hit by the virus, polio survivors may develop the “post-polio syndrome” (PPS), a progressive condition characterized by chronic fatigue and pain, new muscular weakness, and cold intolerance. The etiopathogenesis of PPS is unclear. To check whether PV genomes could persist for decades in polio survivors developing PPS, we used molecular tests, tissue culture studies, and immunoassays with HEV-specific antibody. PVs were detected in samples of 27/27 PPS patients (CSF, peripheral blood leukocytes, saliva, urine) 30 to 75 years from the onset of the disease. Viral sequences and infectivity were not detected in samples of 16 control patients. Analysis of partial sequences revealed that persisting PV genomes were mostly related to the PV type-1 and were markedly different from those of reference strains.

Based on this experience, HEV infections have been investigated in blood samples of 90 children with early stage type 1 diabetes mellitus (T1D). Gene amplification and sequencing showed EV genomes in 86% of the above patients up to one-year from onset, but not in 20 control children. Different HEV types of the B and C species were represented. Cases of temporal and geographic clustering were observed in different years. In some cases, HEV genomes were detected both in probands and their family members. However, diabetes developed only in individuals carrying the high-risk DR3/DR4 HLA aplotypes.

The above data do not prove a causal relationship between chronic HEV infection and PPS or T1D. However, the high prevalence of EV sequences in PPS and diabetic patients indicates that HEVs represent significant biomarkers of both conditions.

Innovative diagnostic methods may pave the way to preventative/therapeutic interventions in order to stop the progression of virus-induced cell damage.

Topic: Bacterial genomic island discovery: a quest with a purpose
Speaker: Dr Kumar RAJAKUMAR, MBBS, MBiotech
Date: Wednesday, 11 June 2008 @ 11:00PM  

Affiliation: PhD, FRCPA, Clinical Senior Lecturer & Honorary Consultant Microbiologist

Department of Infection, Immunity & Inflammation, University of Leicester, United Kingdom

Convenor: Dr. Kevin Tan Shyong Wei

Abstract:
The discovery of genomics islands in virtually every bacterial genome characterized to date challenges our views on what constitutes a bacterial species and provokes the question as to whether 'pathovar' level identification could offer clinical benefits. Given the likely diversity within any one species, the scale of the challenge is enormous. Nevertheless, high-throughput genomics, targeted island discovery programmes and associated functional studies may ultimately define a role for high-resolution pathogen identification in particular settings.

Topic: Analysis of transcription factors in living cells with the help of the split-ubiquitin system
Speaker: Ms. Xue Xiaowei, PhD Candidate
Date: Friday, 23 May 2008 @ 2:00PM  

Affiliation: Department of Microbiology, National University of Singapore

Convenor: Dr. Norbert Lehming

Topic: Innate clearance of ring-infected RBCs by the human spleen and malaria pathogenesis: The spleen microcirculatory factor
Speaker: Dr. Innocent Safeukui
Date: Thursday, 29 May 2008 @ 11:00AM  

Affiliation: Pasteur Institute, France

Convenor: Dr. Kevin Tan S. W.

Topic: Elucidation of the biology of retroviruses and their adaptation as vectors for gene therapy
Speaker: Prof. Walter H Günzburg
Date: Friday, 30 May 2008 @ 12:00PM  

Affiliation: Christian-Doppler Laboratory for Gene Therapeutic Vector Development, Singapore & Vienna

Research Institute for Virology & Biomedicine
University of Veterinary Medicine
Vienna, Austria

Convenor: Dr. Kevin Tan S. W.

Topic: Persistence of mycobacteria in fatty biofilms
Speaker: Dr. Anil Kumar Ojha, PhD, Research Assistant Professor
Convenor: Dr. Norbert Lehming

Affiliation: Department of Biological Sciences, University of Pittsburgh, United States of America

Date: Wednesday, 16 April 2008 @ 11:00AM  4:00PM
           (Please take note of the change in time.)

Abstract:
The extraordinary ability of Mycobacterium tuberculosis (Mtb) to persist during prolonged chemotherapy has been the biggest hurdle in a short and effective treatment of TB. In a novel approach to understand the persistence of Mtb I found that bacilli in biofilms are significantly more tolerant to antibiotic stress as compared to their planktonic counterparts.

This led me to further investigate the molecular basis of biofilm development in Mtb and a closely related species M. smegmatis. Using a combination of genetic and biochemical tools and aided by the techniques of functional genomics, such as microarrays and proteomics, I identified two regulatory mechanisms during the development of M. smegmatis biofilms.

First, a GroEL-1 dependent regulation of mycolic acid synthesis and matrix development during biofilm maturation (Ojha et.al., Cell, 2005, p 861) and second, an iron dependent growth regulation in the early developmental stages (Ojha and Hatfull, Mol. Micro., 2007, p 468).

In another study, I observed that development of Mtb biofilms has distinct genetic and environmental requirements that are not essential for planktonic growth. Furthermore, manipulations of these conditions have direct consequences not only on biofilm formation but also on the development of drug tolerant persisters (manuscript communicated). My future interest is to study the regulatory mechanisms of mycobacterial biofilm development with an aim of identifying drug targets that can be exploited to reduce the frequency of persisters.

During the first few years I will characterize the genetic and environmental factors that control the growth of mycobacterial biofilms- in particular the role of iron in the early developmental stages. From the perspective of basic science, I am interested in fundamental questions about microbial adaptation in a dynamic environment within a complex multicellular structure.

Topic: Development of effective vaccines against Enterovirus 71 (EV71)
Speaker: Mr. Foo Guang Wei Damian, PhD Candidate
Convenor: Dr. Sylvie Alonso

Affiliation: Department of Microbiology, National University of Singapore

Date: Tuesday, 29 April 2008 @ 3:00PM

PhD Open Seminar – Thesis Defense

Topic: Effects of the histones and histone-interactive partners on transcription regulation
Speaker: Ms. He Hongpeng
Convenor: Dr. Norbert Lehming

Affiliation: Department of Microbiology, NUS

Date: Monday, 10 March 2008 @ 3:00PM

*Update: This seminar has been cancelled.

Topic: Messenger RNA cap formation: a potential anti-viral target in negative strand RNA viruses
Speaker: Dr. Li Jianrong

Affiliation: Department of Microbiology & Molecular Genetics Harvard Medical School USA

Date: Wednesday, 12 March 2008 @ 11:00AM

Abstract:
Non-segmented negative-strand (NNS) RNA viruses comprise a number of significant human, animal, and plant pathogens. Examples of NNS RNA viruses include rabies virus, measles virus, canine distemper virus, human respiratory syncytial virus, and Newcastle disease virus, as well as the highly lethal Ebola and Marburg viruses and the newly emerged Nipah and Hendra viruses.

For many of these viruses, there are no effective vaccines or antiviral drugs. NNS RNA viruses utilize a common strategy in gene expression. Viral genomic RNA encapsidated with the nucleocapsid (N) protein to form an N-RNA complex serves as a template for transcription as well as genome replication. The N-RNA complex is recognized by the RNA dependent RNA polymerase (RdRp), whose major components, are the large protein catalytic subunit (L) and the cofactor phosphoprotein (P), to synthesize uncapped leader RNA and capped, methylated, and polyadenylated mRNA. Messenger RNA cap formation of NNS RNA viruses has evolved an unconventional mechanism in which 5' monophosphate RNA is transferred to GDP acceptor by a polyribonucleotidyltransferase.

Working with vesicular stomatitis virus (VSV), we have identified a new motif in conserved region V (CRV) of large polymerase protein plays an essential role in mRNA cap formation. Using a genetic and biochemical approaches, we found that mRNA cap methyltransferase activities are also unique. A single methyltransferase active site in the conserved region VI (CRVI) of large polymerase protein that is essential for both guanine-N-7 and 2’-O methyltransferases. Furthermore, these two methyltransferases share a single S-adenosylmethionine (SAM) binding site.

We also demonstrated that compounds that inhibited viral mRNA methylation diminished virus replication, and that methyltransferase defective VSV mutants are highly attenuated in cell culture. Taken together, these results suggest that mRNA cap formation is an attractive anti-viral target in NNS viruses. A model consistent with these results will also be discussed.

PhD Open Seminar – Thesis Defense

Topic: Development of molecular diagnostics and antiviral therapy against Enterovirus 71 (EV71)
Speaker: Mr. Tan Eng Lee
Convenor: Assoc. Prof. Vincent Chow

Affiliation: Department of Microbiology, NUS

Date: Monday, 24 March 2008 @ 2:00PM

Topic: Development of Anti-Viral Strategies for Dengue and West Nile Viruses
Speaker: Dr. Justin Chu J.H. and Lee Kuan Yew Fellow
Convenor: Dr. Norbert Lehming

Affiliation: Department of Microbiology, NUS

Date: Wednesday, 13 February 2008 @ 11:00AM  

Abstract:
Both dengue and West Nile (WNV) viruses are mosquito-borne flaviviruses that represent important emerging infectious diseases and pose international health concern.  Currently, there is no effective vaccine or anti-viral drugs for these flavivirus infections.

In our first approach, we focused on the characterization of the receptor-binding domain of the West Nile virus envelope (E) protein as a potential target for the development of a subunit vaccine.  Domain III of the WNV E protein was expressed as a recombinant protein and its potential as a subunit vaccine candidate was evaluated in BALB/C mice. This part of our study constitute a proof-of-concept demonstrating that the recombinant WNV E DIII protein delivered in combination with CpG adjuvant to mice generated a Th1 immune response type against WNV and can serve as a potential vaccine to prevent WNV infection.

The alternative approach focused on the development of an effective high-throughput anti-dengue screening platforms.  Towards this end, we have developed a high content imaging platform for dengue virus infection and this platform has been used to screen a structurally diverse collection of bioactive small molecule library.  A number of potential small molecule inhibitors are identified and their effects in dengue virus biology will be presented.  These results indicated that cell-based screening platform may serve as powerful tools in identification of virus and cellular targets and might be the most expeditious route to new anti-dengue therapeutics.

Topic: A tale of two centrins
Speaker: Dr. Cynthia He Yingxin and Assistant Professor

Affiliation: Department of Biological Science, NUS

Date: Wednesday, 20 February 2008 @ 11:00AM  

Abstract:
Centrins are small calcium-binding proteins associated with centrosomes, spindle pole bodies and basal bodies. These highly conserved proteins have been implicated in several cellular functions including organelle duplication, cell signaling and mRNA transport.  In the protozoan parasite Trypanosoma brucei, three Centrins have been found essential for parasite growth. 

Centrin1 is present on the basal bodies which seed the flagellum used for cell locomotion. Centrin2 and Centrin4 are additionally present on a bi-lobed structure closely associated with the single Golgi apparatus in these cells. Interestingly, despite their similarity in sequence and localization, Centrin2 and Centrin4 have very different effects on Golgi duplication and cell division. These differences and possible mechanism will be discussed.

PhD Open Seminar – Thesis Defense

Topic: Mutational analysis of the TATA-binding protein (TBP) in Saccharomyces cerevisiae
Speaker: Ms. Chew Boon Shang
Convenor: Dr. Norbert Lehming

Affiliation: Department of Microbiology, NUS

Date: Friday, 15 February 2008 @ 2:00PM

PhD Open Seminar – Thesis Defense

Topic: Development of a novel Toll-like receptor-based two-hybrid assay for detecting protein-protein interactions and its application in the study of CD14 dimerization and FcyR activation
Speaker: Ms. Linda Wang
Convenor: Assoc. Prof. Lu Jinhua

Affiliation: Department of Microbiology, NUS

Date: Monday, 25 February 2008 @ 3:00PM     

Topic: Staphylococcus aureus and its cell envelope in microbe/host interaction
Speaker: Prof. Andreas Peschel

Affiliation: Cellular and Molecular Microbiology
University of Tubingen (Germany)

Date: Wednesday, 9 January 2008 @ 11:00AM

Abstract:
The skin of humans and warm-blooded animals represents an ecosystem for more than 30 staphylococcal species, which are highly specific for certain host organisms and even certain areas of the skin. Staphylococcus aureus, found in the anterior nares of 30% of the human population, is distinguished by a large number of virulence factors and represents one of the most frequent and dangerous bacterial pathogens.

Many key aspects of staphylococcal physiology, virulence, and immune recognition have remained elusive. The bacterial cell envelope represents a highly variable interface for interactions with environment, other microorganisms, or host factors. Complex macromolecules such as teichoic acids, peptidoglycan, membrane lipids, and surface proteins play crucial roles in many aspects of bacterial physiology and host interaction.

We are studying S. aureus binding to host cells, resistance to innate antimicrobial molecules, and recognition by immune cells by combining molecular biology, biochemistry, cell biology, and chemical analytics. Using staphylococci as model organisms, our research should reveal general principles of microbe/host interaction and may enable novel strategies for preventing and combating microbial infections.

Topic: Coronaviruses found in Hong Kong
Speaker: Prof. Kwok Yung Yuen

Affiliation:State Key Laboratory of Emerging Infectious Diseases, Department of Microbiology, Research Centre of Infection and Immunology
University of Hong Kong (Hong Kong, China)

Date: Tuesday, 29 January 2008 @ 10:30AM

Abstract:
This talk will be a comprehensive review of our research on new coronaviruses including HKU1 and SARS coronavirus (Clinical Microbiology Reviews 2007; 20:660-694).

Venue
Seminar Room @ Level 3
Department of Microbiology
YLL School of Medicine
National University of Singapore
Block MD4, 5 Science Drive 2
Singapore 117597

All Are Welcome!