Alternative splicing generates four different forms of a non-transmembrane protein tyrosine phosphatase mRNA.
PTP-S is a widely expressed non-transmembrane protein tyrosine phosphatase (PTPase), which binds to DNA in vitro. The cellular PTP-S gene product is present mainly in the nucleus in association with chromatin. cDNAs related to PTP-S have been described from human and mouse cells. To establish the origin of molecular diversity in these cDNAs, genomic clones of rat PTP-S were isolated that span over 40 kb of the gene and contain 7 axons. The exon-intron splice sites in the catalytic domain are conserved between PTP-S and human PTP1B. Sequences specific to and homologous to human T-cell PTPase (TC-PTP) were found in the genomic clones of PTP-S, which are expressed in rat cells, as determined by using a specific probe and Northern blot analysis. Analysis of RNA from different rat tissues by reverse transcription-polymerase chain reaction (RT-PCR) showed the presence of four different forms of PTP-S mRNA (named PTP-S1, PTP-S2, PTP-S3, and PTP-S4). PTP-S1 is same as PTP-S reported previously by us. PTP-S2, which is the major form, differs from PTP-S1 in having additional 19 amino acids corresponding to exon E1. PTP-S4 is similar to human T-cell phosphatase. PTP-S3 differs from PTP-S4 in having a deletion of 19 amino acids corresponding to exon E1. Our results suggest that four different forms of PTP-S mRNA arise from a single gene by differential splicing. Two of these forms, PTP-S1 and PTP-S3, were not found in human cells, possibly due to the loss of an internal splice acceptor site in one of the exons, suggesting the occurrence of species-specific splicing in this gene.
Centre for Cellular & Molecular Biology, Hyderabad, India.
R S
RS
Reddy
G
G
Swarup
D017398:Alternative Splicing; D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D002462:Cell Membrane / Q000201:enzymology; D003001:Cloning, Molecular; D017931:DNA Primers; D018076:DNA, Complementary; D006367:HeLa Cells; D006801:Humans; D051379:Mice; D008969:Molecular Sequence Data; D016133:Polymerase Chain Reaction; D017027:Protein Tyrosine Phosphatases / Q000235:genetics*; D012333:RNA, Messenger / Q000235:genetics* / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D017386:Sequence Homology, Amino Acid; D012689:Sequence Homology, Nucleic Acid; D013045:Species Specificity
D017931:DNA Primers; D018076:DNA, Complementary; D012333:RNA, Messenger; D017027:Protein Tyrosine Phosphatases