Molecular cloning, characterization, and chromosomal localization of a novel protein-tyrosine phosphatase, HPTPη

Abstract

Protein-tyrosine phosphatases (PTPases) are considered to play an important role in signal transduction. We previously identified partial sequences of three novel PTPases in a human leukemic cell line, F-36P. We describe here cloning, characterization, and chromosomal localization of one of the newly identified PTPases, termed as HPTPη (human protein-tyrosine phosphatase η). The deduced amino acid sequence was composed of an extracellular region homologous to fibronectin type III repeats, a transmembrane region, and a cytoplasmic region containing a single PTPase- like domain. Based on its primary structure, this clone belongs to type-III receptor-type PTPases. The PTPase-like domain showed PTPase activity when expressed in Escherichia coli. Antibody against the extracellular region detected a protein of 220 to 250 kD in human hematopoietic cell lines expressing HPTPη mRNA. The antibody also recognized a protein of approximately the same molecular weight in COS cells transfected with HPTPη cDNA, indicating that the antibody specifically recognized HPTPη gene product and that the cloned cDNA contained full-length coding region. The chromosomal localization determined by fluorescence in situ hybridization showed that the HPTPη gene was located at chromosome 11p11.2 on the short arm of chromosome 11, which is frequently lost or deleted in human carcinomas.