The type B leukemogenic virus truncated superantigen is dispensable for T-cell lymphomagenesis

Type B leukemogenic virus (TBLV) is a variant of mouse mammary tumor virus (MMTV) that causes T-cell lymphomas in mice. We have constructed a TBLV-MMTV hybrid, pHYB-TBLV, in which 756 bp of the C3H MMTV long terminal repeat (LTR) was replaced with 438 bp of the TBLV LTR. Intraperitoneal injection of pHYB-TBLV transfectants consistently resulted in T-cell lymphomas in 50% of injected weanling BALB/c mice with an average latency period of 5.7 (+/- 1.5) months. Transfectants of pHYB-TBLV containing a double-frameshift mutation in the truncated superantigen gene (sag) induced T-cell lymphomas with similar incidences, latency periods, and phenotypes, suggesting that cis-acting elements in the TBLV LTR determine disease specificity.     

Rorgamma (Rorc) is a common integration site in type B leukemogenic virus-induced T-cell lymphomas

The retrovirus type B leukemogenic virus (TBLV) causes T-cell lymphomas in mice. We have identified the Rorgamma locus as an integration site in 19% of TBLV-induced tumors. Overexpression of one or more Rorgamma isoforms in >77% of the tumors tested may complement apoptotic effects of c-myc overexpression.     

Activation of the human immunodeficiency virus type 1 enhancer is not dependent on NFAT-1.

The function of a putative NFAT-1 site in the human immunodeficiency virus type 1 enhancer has been analyzed. Activation by the T-cell antigen receptor is minimal in Jurkat cells and is mediated by the kappa B sites. The putative NFAT-1 region is not required for the response to anti-CD3 or to mitogens in T-cell, B-cell, or monocyte/macrophage leukemia lines, nor is it a cis-acting negative regulatory element.     

Glycoprotein B is a specific determinant of herpes simplex virus type 1 neuroinvasiveness.

Herpes simplex virus type 1 strains ANG and KOS lack neuroinvasiveness when inoculated on the footpads of mice, and because the strains are able to complement each other, the genes associated with this phenotype differ. In this study, we used marker rescue techniques to show that at least two genes cloned from ANG are required to restore neuroinvasiveness to KOS. One of the two fragments required is the 6.3-kb BamHI-A/EcoRI-D fragment (0.15 to 0.19 map units). The second has been identified as the sequence encoding glycoprotein B (gB) (UL27). Analysis of ANG and KOS DNA sequences in the relevant region of the gB gene revealed two nucleotide differences which result in amino acid differences in the gB protein. One appears to be unique to the strain of KOS used in our laboratory. The second, at codon 523 of the mature gB protein, encodes a valine in KOS and an alanine in ANG. Recombinant KOS viruses which contained ANG sequences in this region were constructed, and two independently selected recombinants demonstrated increased neuroinvasiveness in mice. From these results, we conclude that gB significantly influences neuroinvasiveness. Mechanisms by which this might occur are discussed.     

Herpes simplex virus type 1-mediated induction of human immunodeficiency virus type 1 provirus correlates with binding of nuclear proteins to the NF-kappa B enhancer and leader sequence.

Herpes simplex virus type 1 (HSV-1) infection induces expression of the human immunodeficiency virus type 1 (HIV-1) provirus in the chronically infected T-cell line ACH-2. The HSV-1-mediated induction correlates with the appearance of two NF-kappa B-specific proteins of 55 and 85 kDa in the nucleus and with the binding of 50-kDa nuclear protein to the LBP-1 binding site of the untranslated leader sequence of the HIV-1 long terminal repeat. The HSV-1-induced LBP-1 binding protein, designated HLP-1, is present exclusively in HSV-1-infected, but not in phorbol-12-myristate-13-acetate- or tumor necrosis factor alpha-treated ACH-2 cells. Both the NF-kappa B and LBP-1 target sequences, when inserted either alone or together 5' of a heterologous minimal promoter (thymidine kinase), confer inducibility by HSV-1 infection in a transient transfection assay. Thus, it appears that the HSV-1-mediated activation of HIV-1 provirus is brought about by the binding of both NF-kappa B and HLP-1 specific proteins to two distinct regions of HIV-1 long terminal repeat.     

RUNX3-mediated repression of RUNX1 in B cells

Are there three different RUNX genes in the human genome just to allow differential expression in different cell types or are the RUNX proteins functionally different? Much previous evidence has suggested that the RUNX proteins were functionally redundant but, in human B cells, RUNX1 and RUNX3 have clearly been shown to have different functions at a key developmental stage. RUNX1 is expressed in mature resting B cells but proliferating B cell lines express RUNX3. Repression of RUNX1 by RUNX3 is required to allow the cell proliferation and this provides an experimental system to investigate the mechanism of the different activities of RUNX1 and RUNX3 in these cells. J. Cell. Physiol. 221: 283–287, 2009. © 2009 Wiley-Liss, Inc.     

The Epstein-Barr virus BRLF1 immediate-early gene product transactivates the human immunodeficiency virus type 1 long terminal repeat by a mechanism which is enhancer independent.

The Epstein-Barr virus (EBV) immediate-early gene product, BRLF1, transactivates the human immunodeficiency virus type 1 (HIV-1) long terminal repeat. BRLF1-induced transactivation of HIV-1 promoter constructs is accompanied by an increase in plasmid mRNA and is reporter gene independent. Previously, BRLF1 transactivation of EBV promoters has been mapped to regions which function as enhancer elements. Deletional analysis demonstrates that BRLF1 transactivation of the HIV-1 promoter does not require the HIV-1 enhancer. Thus, the EBV BRLF1 gene product may transactivate by at least two different mechanisms, one mechanism involving certain enhancer elements and another mechanism which is enhancer independent.     

Herpes simplex virus type 1 and pseudorabies virus bind to a common saturable receptor on Vero cells that is not heparan sulfate.

Herpes simplex virus type 1 (HSV-1) and pseudorabies virus (PRV) infect different natural hosts but are very similar in structure, replicative cycle, and entry into cultured cells. We determined whether HSV-1 and PRV use the same cellular components during entry into Vero cells, which are highly susceptible to each virus but are not from native hosts for either. UV-inactivated virions of either HSV-1 or PRV could saturate cell surfaces to block infection of challenge HSV-1 or PRV. In the presence of saturating levels for infection of either virus, radiolabeled virus bound well and in a heparin-sensitive manner. This result shows that heparan sulfate proteoglycans on Vero cells are not the limiting cellular component. To identify the virus component required for blocking, we used an HSV-1 null mutant virus lacking gB, gD, or gH as blocking virus. Virions lacking gB were able to block infection of challenge virus to the same level as did virus containing gB. In contrast, virions lacking gD lost all and most of the ability to block infection of HSV-1 and PRV, respectively. HSV-1 lacking gH and PRV lacking gp50 also were less competent in blocking infection of challenge virus. We conclude that HSV-1 and PRV bind to a common receptor for infection of Vero cells. Although both viruses bind a heparin-like cell component on many cells, including Vero cells, they also attach to a different and limited cell surface component that is bound at least by HSV-1 gD and possibly gH and to some degree by PRV gp50 but not gB. These results clearly demonstrate binding of both HSV-1 and PRV to a common cell receptor that is not heparan sulfate and demonstrate that several types of attachment occur for both viruses during infectious entry.     

Activation of the human immunodeficiency virus long terminal repeat by herpes simplex virus type 1 is associated with induction of a nuclear factor that binds to the NF-kappa B/core enhancer sequence.

It has been previously shown that herpes simplex virus type 1 (HSV-1) infection of HeLa cells results in augmentation of gene expression directed by the human immunodeficiency virus (HIV) long terminal repeat (LTR). This effect is presumably mediated by protein interactions with the LTR. We have used two different assays of DNA-protein interactions to study the HSV-induced activation of the HIV LTR. Activation of the HIV LTR is associated with increased protein binding to LTR sequences in a region including the NF-kappa B/core enhancer and the Sp1 binding sequences as monitored by an exonuclease protection assay. Gel retardation assays demonstrated that HSV-1 infection resulted in the induction of a nuclear factor(s) that binds to the NF-kappa B/core enhancer sequence. In addition to the activation of the HIV LTR, HSV induction of NF-kappa B activity may be important for the regulation of HSV gene expression during a herpesvirus infection.     

Transfection of molecularly cloned Friend murine leukemia virus DNA yields a highly leukemogenic helper-independent type C virus.

Unintegrated viral DNA was isolated via the Hirt procedure from mouse fibroblasts newly infected with Friend murine leukemia virus (F-MuLV) clone 201, a biologically cloned helper virus isolated from stocks of F-MuLV complex. A physical map of the unintegrated in vivo linear viral DNA was generated for several restriction endonucleases. The supercoiled viral DNA was digested with EcoRI, which cleaved the viral DNA at a unique site. The linearized viral DNA was then inserted into lambda gtWES.lambda B at the EcoRI site and cloned in an approved EK2 host. Eight independent lambda-mouse recombinants were identified as containing F-MuLV DNA inserts by hybridization with F-MuLV 32P-labeled complementary DNA. One of the F-MuLV DNA inserts was 9.1 kilobases (kb) and had the same restriction enzyme sites as the unintegrated linear F-MuLV DNA. Six inserts were 8.5 kb; each lacked a single copy of the terminally redundant sequences of the unintegrated linear viral DNA. One insert was 8.2 kb and contained a 0.9-kb deletion. After digestion with EcoRI, one recombinant DNA preparation containing an 8.5-kb insert was infectious for NIH 3T3 cells. Undigested recombinant DNA was not infectious. The infectivity of the EcoRI-digested DNA followed multihit kinetics, indicating that more than one molecule was required to register as an infectious unit. The virus isolated from this transfection (F-MuLV-57) was NB-ecotropic, helper-independent, and formed XC plaques. Inoculation of this virus into newborn NIH Swiss mice induced leukemia and splenomegaly in greater than 90% of animals within 3 to 4 weeks. The gross and microscopic abnormalities induced by F-MuLV clone 57 were identical to those seen with the original parent stocks of F-MuLV clone 201. These results indicate that this helper-independent F-MuLV can induce a rapid nonthymic leukemia in the absence of the spleen focus-forming virus.     

Functional organization of the hepatitis B virus enhancer.

We have studied the functional constituents of the hepatitis B virus enhancer in a number of cell lines. The sequence of this enhancer, being embedded within an open reading frame of the virus, is in part evolutionarily frozen and therefore serves as a good model to investigate the fundamental enhancer elements. The hepatitis B virus enhancer contains three functionally important DNA sequence elements, EP, E, and NF-1a, each of which is bound by a distinct protein(s). The synergistic action of these elements accounts for all of the enhancer activity in a nonliver cell line and for most, but not all, of the activity in liver-derived cell lines. Multimers of the E but not of the EP element act as an autonomous enhancer. Conversely, a single element of either the E or the NF-1a element can act only when linked to the EP element. These results suggest that EP is a crucial enhancer element that acts only in interaction with a second enhancer element with intrinsic enhancer activity. Interestingly, a highly similar enhancer structure is found in a number of distinct viruses.