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J. Virol., Oct 1995, 6199-6208, Vol 69, No. 10
D Mackey, T Middleton and B Sugden
Epstein-Barr virus nuclear antigen 1 (EBNA1) can bind specifically to two
clusters of sites within the Epstein-Barr virus plasmid origin of DNA
replication (oriP). EBNA1 activates DNA replication mediated by oriP and
can also activate transcription and retain DNA in cells when bound site
specifically. EBNA1 bound to oriP physically links the two clusters of
EBNA1-binding sites, resulting in loop formation by the intervening DNA. To
elucidate the contribution of DNA linking by EBNA1 to its biological
activities, we identified regions within it that can independently link
DNAs to which they are bound. An electrophoretic mobility shift assay was
used to detect this activity. Proteins which link DNA aggregate that DNA
into large lattices. Proteins which cannot link DNA but still bind to DNA
retard the mobility of that DNA but do not cause it to form lattices.
Amino-terminal truncations were used to map the amino-terminal limit of a
minimal DNA-linking domain approximately to amino acid 372 of EBNA1. To map
the carboxy-terminal limit of this minimal domain, fusion proteins
containing the DNA- binding domain of GAL4 and fragments of EBNA1 were
generated and studied. This approach identified the carboxy-terminal limit
of this minimal domain to be approximately amino acid 391 and verified its
amino-terminal limit. Internal deletions within a truncated EBNA1
derivative verified the importance of this region. Two additional fragments
of EBNA1, each of which independently conferred DNA-linking activity on the
domain of GAL4 which binds DNA, were identified within amino acids 54 to 89
and amino acids 331 to 361. Therefore, EBNA1 contains at least three
regions that can act independently to link DNAs and that may act in concert
within intact EBNA1.
Copyright © 1995, American Society for Microbiology
Multiple regions within EBNA1 can link DNAs
McArdle Laboratory for Cancer Research, Department of Oncology, Medical School, University of Wisconsin-Madison, USA.
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