The effect of vpu on HIV-1-induced syncytia formation

Article Abstract:

Expression of the gene for viral protein u (vpu) appears to inhibit the ability of human immunodeficiency virus type 1 (HIV-1) to kill human T cells. HIV-1 kills cells by initiating the formation of giant cells with many nuclei and the merging of many cells known as syncytia. Later in the infection, HIV-1 destroys single cells. In a laboratory experiment, human T cells, which play a critical role in the body's immune system, were infected with viruses which were identical except for their ability to produce vpu. T cells infected with the virus that could produce vpu released more HIV-1 particles than cells infected with the virus that could not produce vpu. However, the rate of syncytia formation, and thus cell killing, was lower among cells infected with HIV-1 that could produce vpu than among cells infected with HIV-1 that could not produce vpu. The rate of single cell killing was not affected by vpu production.

Research, Gene expression, Viral envelopes

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Selective effects on DNA damaging agents on HIV long terminal repeat activation and virus replication in vitro

Article Abstract:

Several drugs used in chemotherapy appear capable of activating the AIDS virus. HIV reproduction is activated by a stretch of nucleic acid called the long terminal repeat (LTR). Researchers tested several chemotherapy drugs that damage DNA to see if the drugs activated the LTR in cell cultures. The drugs included mitomycin C (MMC), methotrexate, cisplatinum (II) diammine dichloride (CDDP), daunorubicin, doxorubicin, methylmethane sulfonate (MMS), etoposide and ara-C. They also tested ionizing radiation and hydrogen peroxide, which can also damage DNA. Most of the drugs did not cause significant LTR activation. However, MMC and CDDP did cause significant activation and daunorubicin and doxorubicin activated LTR to a lesser degree. Ionizing radiation and hydrogen peroxide had little effect on LTR activation. AIDS patients with cancer often receive chemotherapy, but such treatment could enhance HIV replication.

Antineoplastic agents, Virus replication

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Functional analysis of the phosphorylation sites on the human immunodeficiency virus type 1 Vpu protein

Article Abstract:

The HIV Vpu protein phosphorylation sites appear to play a role in regulating syncytium formation, but not in the release of new virus particles (virions). Syncytium formation, the result of cell unions, and virion release are steps in the reproduction cycle of HIV. Researchers determined that Vpu is phosphorylated at two serine sites, Ser 52 and Ser 56, in the amino acid sequence of the protein. They mutated the sequences at Ser 56 and both Ser 56 and Ser 52 using genetic engineering techniques and assayed for changes in syncytium formation and virion release in transfected cell lines. The rate of syncytium formation was more rapid in the cultures with the mutated sequences than in those with the natural protein sequence. Virion release, however, was not affected by the mutations. These two activities seem to be mediated by independent functions of Vpu.

Proteins

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