Yu-Ying Kong

Prospero-related homeobox protein (Prox1) inhibits hepatitis B virus replication through repressing multiple cis regulatory elements

Hepatitis B virus (HBV) gene transcription is controlled by viral promoters and enhancers, the activities of which are regulated by a number of cellular factors as well as virally encoded proteins. Negative regulation of HBV cis-element activities by cellular factors has been reported less widely than their activation. In this study, we report that nuclear factor Prospero-related homeobox protein (Prox1) represses HBV antigen expression and genome replication in cultured hepatocytes. By using reporter-gene analysis, three of the four HBV promoters, namely the enhancer II/core promoter (ENII/Cp), preS1 promoter (Sp1) and enhancer I/X promoter, were identified as targets for Prox1-mediated repression. Mechanistic analysis then revealed that, for ENII/Cp, Prox1 serves as a corepressor of liver receptor homologue 1 (LRH-1) and downregulates LRH-1-mediated activation of ENII/Cp, whereas for Sp1, Prox1 partially represses Sp1 activity by interacting directly with hepatocyte nuclear factor 1. Identification of Prox1 as an HBV repressor will help in the understanding of detailed interactions between viral cis elements and host cellular factors and may also form the basis for new anti-HBV intervention therapeutics.

Expression of mouse liver receptor homologue 1 in embryonic stem cells is directed by a novel promoter

Liver receptor homologue 1 (LRH‐1) plays important roles in many physiological processes and embryogenesis. However, little is known about the developmental regulation of lrh‐1 expression. We identified a novel transcript of mouse lrh‐1 (mlrh‐1v2) from embryonic stem (ES) cells. mlrh‐1v2 is expressed throughout embryogenesis and in several adult tissues, while the known transcript (mlrh‐1v1) appears later during embryogenesis. mlrh‐1v2 expression is directed by a new promoter which displays a strong activity in ES cells. The generation of the new transcript is conserved in rats. The identification of novel mlrh‐1 variant and promoter is critical for elucidating LRH‐1 functions in development and adult tissues.

Expression, Purification and Sublocalization of SARS-CoV Nucleocapsid Protein in Insect Cells

Abstract The causative agent of severe acute respiratory syndrome (SARS) is a previously unidentified coronavirus, SARS-CoV. The nucleocapsid (N) protein of SARS-CoV is a major viral protein recognized by acute and early convalescent sera from SARS patients. To facilitate the studies on the function and structure of the N protein, this report describe the expression and purification of recombinant SARS-CoV N protein using the baculovirus expression system. Recombinant hexa-histidine-tagged N protein with a molecular mass of 47 kD was produced in insect cells. Recombinant N protein was purified to near homogeneity by Ni2+-NTA affinity chromatography. In addition, we examined the subcellular localization of the N protein by confocal microscopy in Trichoplusia ni BT1 Tn 5B1–4 cells infected with recombinant baculovirus. The N protein was found localized in the cytoplasm as well as in the nucleolus. The purified recombinant N protein can be used in further functional study of SARS-CoV.

Characterization of a novel isoform of murine interferon regulatory factor 3

Interferon (IFN) regulatory factors (IRFs) are a family of transcription mediators involved in the regulation of type I IFN (IFN-alpha/beta) transcription. Among the nine already identified IRFs, IRF-3 is a constitutively and ubiquitously expressed and plays a critical role in the transcriptional activation of type I IFN and IFN-stimulated genes including IFN-alpha1, IFN-beta and RANTES. In the present study, we report the identification of a novel alternatively spliced transcript of murine Irf-3 gene (mIrf-3) designated mIRF-3a. mIRF-3a is ubiquitously present in mouse tissues along with mIRF-3 and could be translocated into the nucleus in uninfected L929 cells. EMSA and reporter assay demonstrated that mIRF-3a binds to ISRE sequences in murine Ifn-beta promoter and represses Ifn-beta promoter activation induced by Newcastle disease virus infection. These results suggest that mIRF-3a may act as a modulator of mIRF-3 functions in vivo.