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WT1 is also essential for the development of the urogenital
system. WT1 binds specifically to G+C- or T+C-rich elements
in promoter sequences of certain genes and causes either
repression or activation of their transcription. Using
the simian virus 40 (SV40) replication assay system,
we have discovered a novel activity of WT1 as an inhibitor
of DNA replication. All of the domains of WT1 required
for its transcriptional regulatory function were also
found to be required for its replication inhibition
function. Inhibition of replication did not require
the specific binding of WT1 to the replication origin
region. Unlike tumor suppressor protein p53, which also
inhibits SV40 origin-dependent DNA replication, WT1
neither associated physically with the SV40 replication
initiation protein large T antigen nor interfered with
the latter’s replication initiation function. We have
developed monkey kidney cell lines containing integrated
copies of a wt1 gene-containing plasmid that
can be made to overexpress WT1 via autonomous replication
of the plasmid and inducible transcriptional stimulation
of the gene. Using this system, we find that WT1 inhibits
DNA replication directly, as well as indirectly by causing
loss of replicated DNA as a consequence of cell death
induced by this protein. In collaboration with another
laboratory, we are also investigating the requirement
of WT1 for the optimal function of a T lymphocyte-specific
transcriptional enhancer sequence.
Selected Publications:
Lee, N-G., Yamaguchi, J., and Subramanian, K.N. (1991).
Efficient replication of plasmids containing the SV40
origin in N-Myc overexpressing human neuroblastoma cells.
Oncogene, 6: 1161-1169.
Anant, S., Axenovich, S.A., Madden, S.L., Rauscher,
F.J., III, and Subramanian, K.N. (1994). Novel replication
inhibitory function of the developmental regulator/transcription
repressor protein WT1 encoded by the Wilms’ tumor gene.
Oncogene, 9: 3113-3126.
Murthy, N., Subramanian, U., Anant, S., and Subramanian,
K.N. (1998). The replication inhibition function of
the WT1 tumor suppressor protein resides in its N-terminal
298 amino acid region, and does not require specific
binding of the protein to the replication origin sequence.
Int. J. Oncol. 13: 1275-1280.
Basu, S., Ramaswamy, S., and Subramanian, K.N. (1999).
Tumor suppressor protein WT1 inhibits autonomous DNA
replication directly, as well as indirectly by causing
loss of replicated DNA as a consequence of cell death
induced by the protein. Int. J. Oncol. 15: 701-708.
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