CHROMOSOMAL LOCALIZATION OF THE PROTEIN-TYROSINE-PHOSPHATASE G1 GENE AND CHARACTERIZATION OF THE ABERRANT TRANSCRIPTS IN HUMAN COLON-CANCERCELLS

We have recently,described the isolation of the human PTPG1 gene which encodes a member of intracellular protein tyrosine phosphatases that may be candidates for tumor suppressor genes. In order to investigate the abnormality of the PTPG1 transcript in various human cancer cell l ines, we have analyzed the consensus catalytic region of PTPG1 cDNA, u sing the reverse transcriptionpolymerase chain reaction. In a colorect al carcinoma cell line, DLD-1, we found three aberrant transcripts. Se quencing analysis revealed that one had a missense point mutation and the remainders contained 77 bp and 173 bp deletions, respectively. The se alterations might directly affect their phosphatase activities. Our findings provide the first evidence for the aberrant transcripts of t he protein tyrosine phosphatase in human cancer cells, and suggest tha t the aberration of PTPG1 gene might be involved in the tumororigenesi s. Moreover, the human PTPG1 gene is localized on chromosome 7q11.23, a region with frequent abnormalities implicated in some human cancers.