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p53 protein is encoded by a tumor-suppressor gene located on the short arm of chromosome 17. We looked for mutations or rearrangements of the p53 gene in five patients with acute transformation of a chronic myeloproliferative disorder and cytogenetic anomalies involving the short arm of chromosome 17. Two patients had a isochromosome i(17q); three more patients showed the presence of unbalanced translocations involving chromosome 17. One of these patients had a single base pair deletion, causing a frameshift mutation, in the exon 5 of the p53 gene. The karyotype of this patient showed a translocation t(5;17)(q11;p11), with loss of a normal homologue of both chromosomes 5 and 17. In all other cases the configuration of the p53 gene, as tested by PCR-SSCP analysis of exons 5 to 9 and Southern blot, was normal. Our data suggest that mutations of the p53 gene occur in a minority of hemopoietic malignancies characterized by monosomy for the short arm of chromosome 17. However, the unbalanced translocation t(5q;17p) could be a chromosomal abnormality specifically associated with loss of function of the p53 gene. |
