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The large subunit of herpes simplex virus type 2 ribonucleotide reductase (ICP10) is a multifunctional protein that contains a serine-threonine protein kinase (PK) activity (Nelson, J. W., Zhu, J., Smith, C. C., Kulka, M., and Aurelian, L. (1996) J. Biol. Chem. 271, 17021-17027). Phylogenetic analyses indicated that ICP10 PK belongs to a distinct subfamily of growth factor receptor serine-threonine PKs that are characterized by their ability to function with a limited number of conserved catalytic motifs (Hunter, J. C. R., Smith, C. C., and Aurelian, L. (1995) Int. J. Onc. 7, 515-522). Here, we report the isolation and characterization of a novel gene, designated H11, that contains an open reading frame of 588 nucleotides, which encodes a protein similar to ICP10 PK. The H11 protein has Mn 2؉ -dependent serinethreonine-specific PK activity as determined with a GST-H11 fusion protein and by immununocomplex PK/ immunoblotting assays of 293 cells transfected with a H11 eukaryotic expression vector. PK activity is ablated by mutation of Lys 113 within the presumtive catalytic motif II (invariant Lys). 293 cells stably transfected with H11 acquire anchorage-independent growth. Endogenous H11 RNA and the H11 phosphoprotein are expressed in melanoma cell lines and primary melanoma tissues at levels higher than in normal melanocytes and in benign nevi. Melanoma cell proliferation is inhibited by treatment with antisense oligonucleotides that inhibit H11 translation, suggesting that H11 expression is associated with cell growth.Several herpes viruses including herpes simplex virus type 1 (HSV-1) 1 and herpes simplex virus type 2 (HSV-2) express a distinct ribonucleotide reductase activity formed by the association of a large (R1) and a small (R2) subunit. The HSV-2 R1 gene (also known as ICP10) differs from its counterparts in eukaryotic and prokaryotic cells and in other viruses in that it possesses a unique one-third 5Ј-terminal domain (1) that codes for a serine (Ser)-threonine (Thr) protein kinase (PK) (2-8) and causes neoplastic transformation of immortalized cells (9 -11). Unlike other known PKs that have at least 12 conserved catalytic motifs (12, 13), ICP10 PK functions with only eight such motifs. They are clustered close to the N terminus, downstream of a transmembrane (TM) domain and surround a Src homology region 3-binding module (2,4,6,14). The ICP10 PK activity is Mn 2ϩ ion-dependent, does not require monovalent cations, and is not inhibited by zinc sulfate, properties distinct from those of many cellular kinases such as casein kinase II (5). ICP10 is located on the cell surface and its PK activity is intrinsic. Mutants in which the TM domain or the conserved PK catalytic motifs were deleted or otherwise altered were rendered PK negative (4,5,7,8), and the PK activity of a chimeric protein consisting of ICP10 PK and the ligand-binding domain of the epidermal growth factor receptor was activated by epidermal growth factor (15). Most significantly, the ICP10 PK activity was ablated by mutation of the invarian...

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Triterpenoids and flavonoids isolated from Alnus firma S. Z. were found to inhibit HIV-1 virus replication and controlled its essential enzymes. In this study, the inhibition of HIV-1 viral replication and its essential enzymes, such as reverse transcriptase, protease and alpha-glucosidase, were observed using 18 Korean plant extracts. Among the extracts, the methanol extract of Alnus firma leaves showed potent inhibition against the HIV-1 induced cytopathic effect (CPE) in MT-4 cells on microscopic observation (the minimum concentration for complete inhibition of HIV-1 induced CPE, IC=50 microg/mL). Thus, 14 compounds were isolated and identified from the methanol extract of Alnus firma leaves. Of these compounds, the alnustic acid methyl ester exhibited inhibition against HIV-1 protease, with an IC50 of 15.8 microM, and quercetin, quercitrin and myricetin 3-O-beta-D-galactopyranoside displayed inhibition against HIV-1 reverse transcriptase, all with IC50 values of 60 microM. Based on these results, the viral replication inhibition of the methanol extract of Alnus firma leaves was adjudged to be acutely related to the protease inhibition activation of the alnustic acid methyl ester as well as the reverse transcriptase inhibition activation of flavonoids.