Molecular cloning of a novel protein‐tyrosine phosphatase SH‐PTP3 with sequence similarity to the src‐homology region 2

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Abstract
Protein‐tyrosine phosphorylation and dephosphorylation are directly associated with cellular growth, signal transduction, and neoplastic transformation. Here we report the isolation of a complementary DNA (cDNA) clone encoding a novel protein‐tyrosine phosphatase (PTP) from a human T cell PEER cDNA library. The predicted open reading frame encodes a ∼68‐kDa protein composed of 593 amino acids which contains two src‐homology region 2's (SH2 domains) at the N terminus; this PTP is designated as SH‐PTP3. Northern blot analysis revealed that SH‐PTP3 mRNA was expressed throughout many tissues and the transcriptional size was consistent at about 6.0 kb. As with other SH2 domains in src‐family kinases, the SH2 domains of SH‐PTP3 may play a crucial role in interactions with tyrosine phosphorylated signaling proteins, including itself and protein tyrosine kinases (PTKs), to regulate tarpets' enzyme activity.