EXPRESSION AND CHROMOSOMAL ASSIGNMENT OF PTPH1 GENE ENCODING A CYTOSOLIC PROTEIN-TYROSINE-PHOSPHATASE HOMOLOGOUS TO CYTOSKELETAL-ASSOCIATEDPROTEINS

We have investigated the mRNA expression of 2 human protein tyrosine p hosphatases with sequence homology to cytoskeletal proteins, PTPH1 and PTPMEG. Northern-blot analysis of PTPH1 using poly (A)+ RNA from norm al human colon tissue showed a low-abundance message of 4.3 kb. Revers e-transcriptase/polymerase-chain reaction (RT-PCR) was therefore used to detect it in a wide variety of cell lines including 9 colorectal, 5 gastric, 5 hepatic and 6 hematopoietic tumor cells. PTPH1 mRNA was no t detected only in Colo 320 cells over-expressing c-myc mRNA, among th e colorectal cancer cell lines examined. When Colo 320 cells were incu bated with 5 mM sodium butyrate for 5 days, PTPH1 mRNA became detectab le, concomitant with the marked decrease in the expression level of c- myc mRNA. Moreover, the chromosomal localization of PTPH1 gene was inv estigated by fluorescence in situ hybridization. Interestingly, PTPH1 gene was mapped to 9q31 where the gene for Gorlin syndrome, a putative tumor suppressor gene, exists. (C) 1993 Wiley-Liss, Inc.