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J. Virol., May 1995, 2842-2849, Vol 69, No. 5
PE Rose and BS Schaffhausen
Polyomavirus large tumor antigen (LT) contains a potential C2H2 zinc
binding element between residues 452 and 472. LT also contains a third
histidine in this region, conserved among the polyomavirus LTs. Synthetic
peptides of this region bound a single atom of zinc, as determined by
spectroscopic analysis. Blotting experiments also showed that fusion
proteins containing the element, as well as full-length LT, bound 65Zn.
Polyomavirus middle T and small T antigens also bound zinc in the blotting
assay. Site-directed mutagenesis showed the importance of this element in
LT. Point mutations in four of the conserved residues (C-452, C-455, H-465,
and H-469) blocked the ability of LT to function in viral DNA replication,
while mutation of H-472-->L decreased replication to 1/30th that of the
wild type. Point mutations in intervening residues tested had little effect
on replication. Mutants resulting from mutations in the conserved cysteine
or histidine residues retained the ability to bind origin DNA. However,
they did show a defect in self-association. Because double-hexamer
formation is involved in DNA replication, this deficiency is sufficient to
explain the defect in replication. Mutants created by point mutations of
the coordinating residues were also deficient in replication-associated
phosphorylations.
Copyright © 1995, American Society for Microbiology
Zinc-binding and protein-protein interactions mediated by the polyomavirus large T antigen zinc finger
Department of Biochemistry, Sackler School of Graduate Biomedical Sciences, Tufts University School of Medicine, Boston, Massachusetts 02111, USA.
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