Abstract
In searching for cellular targets of the HTLV-I oncoprotein Tax, we identified TXBP181, which we characterized as the human homolog of yeast mitotic checkpoint MAD1 protein. Evidence supporting TXBP181 as HsMAD1 includes sequence conservation with yeast MAD1, hyperphosphorylation during S/G2/M phases and upon treatment of cells with nocodazole, and binding to HsMAD2. HsMAD1 functions as a homodimer. It localizes to the centrosome during metaphase and to the spindle midzone and the midbody during anaphase and telophase. Expression of either Tax or a transdominant-negative TXBP181 results in multinucleated cells, a phenotype consistent with a loss of HsMAD1 function. We propose a model of viral transformation in which Tax targets TXBP181, thereby abrogating a mitotic checkpoint.
MeSH terms
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Amino Acid Sequence
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Animals
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Binding Sites
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Carrier Proteins / chemistry*
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Carrier Proteins / metabolism*
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Cell Cycle / physiology
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Cell Cycle Proteins*
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Conserved Sequence
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Gene Products, tax / chemistry
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Gene Products, tax / metabolism*
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HeLa Cells
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Human T-lymphotropic virus 1 / metabolism*
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Humans
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Mammals
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Mitosis
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Molecular Sequence Data
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Nocodazole / pharmacology
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Nuclear Proteins / chemistry
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Nuclear Proteins / metabolism
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Phosphoproteins / chemistry*
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Phosphoproteins / metabolism*
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Phosphorylation
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Polymerase Chain Reaction
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Recombinant Fusion Proteins / chemistry
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Recombinant Fusion Proteins / metabolism
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Repressor Proteins*
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Saccharomyces cerevisiae / metabolism
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Saccharomyces cerevisiae Proteins
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Sequence Alignment
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Sequence Homology, Amino Acid
Substances
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Carrier Proteins
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Cell Cycle Proteins
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Gene Products, tax
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MAD1 protein, S cerevisiae
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MAD1L1 protein, human
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Nuclear Proteins
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Phosphoproteins
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Recombinant Fusion Proteins
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Repressor Proteins
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Saccharomyces cerevisiae Proteins
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Nocodazole
Associated data
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GENBANK/AF083811
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GENBANK/U31278
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GENBANK/U33822