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Title
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Biological properties of human c-Ha-ras1 genes mutated at codon 12.
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Authors
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P.H.Seeburg,
W.W.Colby,
D.J.Capon,
D.V.Goeddel,
A.D.Levinson.
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Ref.
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Nature, 1984,
312,
71-75.
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PubMed id
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Abstract
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Vertebrate genomes contain proto-oncogenes whose enhanced expression or
alteration by mutation seems to be involved in the development of naturally
occurring tumours. These activated genes, usually assayed by their ability to
induce the malignant transformation of NIH 3T3 cells, are frequently related to
the ras oncogene of Harvey (Ha-ras) or Kirsten (Ki-ras) murine sarcoma viruses,
or a third member of this family (N-ras). Activation involves point mutation
which often affect codon 12 (refs 16-26) of the encoded 21,000-molecular weight
polypeptide (p21). To provide insight into structural requirements involved in
p21 activation, we have now constructed 20 mutant c-Ha-ras1 genes by in vitro
mutagenesis, each encoding a different amino acid at codon 12. Analysis of rat
fibroblasts transfected with these altered genes demonstrates that all amino
acids except glycine (which is encoded by normal cellular ras genes) and proline
at position 12 activate p21, suggesting a requirement for an alpha-helical
structure in this region of the polypeptide. The morphological phenotype of
cells transformed by the activated genes can, however, depend on the particular
amino acid at this position.
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