No abstract

A human myelomonocytic cell line, U937, produced an interleukin-1 (IL-1) receptor antagonist protein (IRAP) which was purified and partially sequenced. A complementary DNA coding for IRAP was cloned and sequenced. The mature translation product of the cDNA has been expressed in Escherichia coli and was an active competitive inhibitor of the binding of IL-1 to the T-cell/fibroblast form of the IL-1 receptor. Recombinant IRAP specifically inhibited IL-1 bioactivity on T cells and endothelial cells in vitro and was a potent inhibitor of IL-1 induced corticosterone production in vivo.

Herpesviruses are the second leading cause of human viral diseases. Herpes Simplex Virus types 1 and 2 and Varicella-zoster virus produce neurotropic infections such as cutaneous and genital herpes, chickenpox, and shingles. Infections of a lymphotropic nature are caused by cytomegalovirus, HSV-6, HSV-7, and Epstein-Barr virus producing lymphoma, carcinoma, and congenital abnormalities. Yet another series of serious health problems are posed by infections in immunocompromised individuals. Common therapies for herpes viral infections employ nucleoside analogs, such as Acyclovir, and target the viral DNA polymerase, essential for viral DNA replication. Although clinically useful, this class of drugs exhibits a narrow antiviral spectrum, and resistance to these agents is an emerging problem for disease management. A better understanding of herpes virus replication will help the development of new safe and effective broad spectrum anti-herpetic drugs that fill an unmet need. Here, we present the first crystal structure of a herpesvirus polymerase, the Herpes Simplex Virus type 1 DNA polymerase, at 2.7 Å resolution. The structural similarity of this polymerase to other ␣ polymerases has allowed us to construct high confidence models of a replication complex of the polymerase and of Acyclovir as a DNA chain terminator. We propose a novel inhibition mechanism in which a representative of a series of non-nucleosidic viral polymerase inhibitors, the 4-oxo-dihydroquinolines, binds at the polymerase active site interacting non-covalently with both the polymerase and the DNA duplex.

We have recently shown that hsp56, the FK506-binding immunophilin component of both the heat shock protein (hsp90.hsp70.hsp56) heterocomplex and the untransformed glucocorticoid receptor heterocomplex, is bound directly to hsp90 (Czar, M. J., Owens-Grillo, J. K., Dittmar, K. D., Hutchison, K. A., Zacharek, A. M., Leach, K. L., Deibel, M. R., and Pratt, W. B. (1994) J. Biol. Chem. 269, 11155-11161). In this work, we show that both untransformed glucocorticoid receptor and hsp90 heterocomplexes contain CyP-40, a 40-kDa immunophilin of the cyclosporin A-binding class. CyP-40 is present in both native glucocorticoid receptor heterocomplexes and receptor heterocomplexes reconstituted with rabbit reticulocyte lysate, and the presence of CyP-40 in the receptor heterocomplex is stabilized by molybdate. Immunoadsorption of hsp90 from cell lysate yields coimmunoadsorption of both hsp56 and CyP-40, showing that both immunophilins are in native heterocomplex with hsp90. However, immunoadsorption of hsp56 does not yield coimmunoadsorption of CyP-40; thus, the two immunophilins do not exist in the same heterocomplex with hsp90. Both purified CyP-40 and hsp56 bind directly to purified hsp90, and excess CyP-40 blocks the binding of hsp56, consistent with the presence of a common immunophilin binding site on hsp90. Our data also suggest that there are at least two types of untransformed glucocorticoid receptor-hsp90 heterocomplexes, one that contains hsp56 and another that contains CyP-40. The role played by the immunophilins in steroid receptor action is unknown, but it is clear that the peptidylprolyl isomerase activity of immunophilins is not required for glucocorticoid receptor-hsp90 heterocomplex assembly and proper folding of the hormone binding domain by the hsp90-associated protein folding system of reticulocyte lysate.

The bis(heteroaryl)piperazine U-88204E is a potent inhibitor of HIV-1 reverse transcriptase (RT) and possesses excellent anti-HIV activity in HIV-1-infected lymphocytes grown in tissue culture. Enzymatic kinetic studies of the RNA- and DNA-dependent DNA polymerases of RT were carried out in order to determine whether the inhibitor interacts directly with the template:primer or deoxyribonucleotide triphosphate (dNTP) binding sites of the polymerase. The experimental results were analyzed using steady-state or Briggs-Haldane kinetics, by assuming that the template:primer binds to the enzyme first followed by the dNTP and that the polymerase functions processively. The results of the analysis show that the inhibitor acts as a mixed to noncompetitive inhibitor with respect to both the template:primer and the dNTP binding sites. The potency of U-88204E on the RNA-directed DNA polymerase activity depends on the base composition of the template:primer. The Ki values for the poly(rC):(dG)10-directed reactions were at least 7 times lower than the ones for reactions directed by poly(rA):(dT)10. The inhibitor did not inhibit the RNase H function of HIV-1 RT nor did it impair the RNA-directed DNA polymerase activity of HIV-2 RT. These data thus demonstrate the unique specificity of U-88204E for HIV-1 RT.