Abstract
We identified a novel gene encoding protein-tyrosine phosphatase using a polymerase chain reaction-based method. Northern blot hybridization of RNAs from various tissues with the polymerase chain reaction-amplified DNA fragment showed that this gene was expressed exclusively in the testis. Complementary DNAs for this gene, termed typ (testis-specific tyrosine phosphatase), were obtained from a mouse testis cDNA library. Nucleotide sequencing of the cDNAs revealed an open reading frame that encoded 426 amino acids. The predicted Typ protein contained a single catalytic domain at the carboxyl-terminal half. No hydrophobic stretch for a possible transmembrane sequence or signal sequence was found, suggesting that Typ is a cytoplasmic protein-tyrosine phosphatase. The amino-terminal half of Typ did not share significant homologies with the other known proteins but contained a region rich in PEST residues. Indirect immunofluorescence studies and in situ hybridization analysis showed that Typ was specifically expressed in testicular germ cells that underwent meiosis. Developmentally, Typ was detected between 2 and 3 weeks after birth, in parallel with the onset of meiosis. Thus, Typ is a new member of the cytoplasmic protein-tyrosine phosphatases that may play an important role(s) in spermatogenesis and/or meiosis.
Highlights
Protein tyrosine phosphorylation is one of the important regulatory events in cell growth, activation, and differentiation [1]
The typ gene is expressed in spermatocytes that are under meiosis, suggesting an important role of the Typ protein in spermatogenesis
The RT reaction was primed with a degenerate primer designed from amino acid sequence QRE(A/E/D)Q, which was conserved among protein-tyrosine phosphatases (PTPs)
Summary
Protein tyrosine phosphorylation is one of the important regulatory events in cell growth, activation, and differentiation [1]. The typ gene is expressed in spermatocytes that are under meiosis, suggesting an important role of the Typ protein in spermatogenesis. Using the 32P-labeled cDNA insert of clone 5 as a probe, typ mRNA of 3.2 kilobases, the same size as that detected in human testis, was detected only in testis among seven tissues examined (Fig. 1B).
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