Human 18 kDa phosphotyrosine protein phosphatase (ACP1) polymorphism: studies of rare variants provide evidence that substitutions within or near alternatively spliced exons affect splicing result

The nature of the suppression of platelet-derived growth factor (PDGF) receptor autophosphorylation in ras-transformed NIH 3T3 fibroblasts was investigated. The PDGF receptor from ras-transformed cells that had been purified by wheatgerm-lectin affinity chromatography displayed normal PDGF-induced autophosphorylation, indicating that the receptor is not irreversibly modified. Various phosphotyrosine-protein-phosphatase inhibitors did not reverse the inhibition of PDGF-receptor kinase in crude membrane preparations from ras-transformed cells. However, treatment of intact ras-transformed cells both with 2 mM sodium orthovanadate and with 20 microM phenylarsine oxide restored PDGF-receptor tyrosine-kinase activity to a level similar to that observed in normal cells. Direct measurement of the phosphatase activities in crude cellular fractions revealed a 2.5-fold higher membrane-associated phosphotyrosine-protein-phosphatase activity in ras-transformed cells, whereas phosphoserine-protein-phosphatase activity remained unchanged between the cell lines. These data suggest that the suppression of the PDGF-receptor tyrosine-kinase activity in ras-transformed cells is mediated via an inhibitory component, distinct from the receptor, that may be positively regulated by the dephosphorylation of tyrosine residue(s).

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Positive Selection in Alternatively Spliced Exons of Human Genes

The American Journal of Human Genetics ◽

10.1016/j.ajhg.2008.05.017 ◽

2008 ◽

Vol 83 (1) ◽

pp. 94-98 ◽

Cited By ~ 15

Author(s):

Vasily E. Ramensky ◽

Ramil N. Nurtdinov ◽

Alexei D. Neverov ◽

Andrei A. Mironov ◽

Mikhail S. Gelfand

Keyword(s):

Positive Selection ◽

Human Genes ◽

Alternatively Spliced ◽

Alternatively Spliced Exons

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Elements regulating an alternatively spliced exon of the rat fibronectin gene

Molecular and Cellular Biology ◽

10.1128/mcb.13.9.5301-5314.1993 ◽

1993 ◽

Vol 13 (9) ◽

pp. 5301-5314 ◽

Cited By ~ 1

Author(s):

G S Huh ◽

R O Hynes

Keyword(s):

Splice Sites ◽

Cell Type ◽

Long Distance ◽

Sequence Elements ◽

Alternatively Spliced ◽

A Cell ◽

Cell Type Specific ◽

Alternatively Spliced Exons

We have investigated the regulation of splicing of one of the alternatively spliced exons in the rat fibronectin gene, the EIIIB exon. This 273-nucleotide exon is excluded by some cells and included to various degrees by others. We find that EIIIB is intrinsically poorly spliced and that both its exon sequences and its splice sites contribute to its poor recognition. Therefore, cells which recognize the EIIIB exon must have mechanisms for improving its splicing. Furthermore, in order for EIIB to be regulated, a balance must exist between the EIIIB splice sites and those of its flanking exons. Although the intron upstream of EIIIB does not appear to play a role in the recognition of EIIIB for splicing, the intron downstream contains sequence elements which can promote EIIIB recognition in a cell-type-specific fashion. These elements are located an unusually long distance from the exon that they regulate, more than 518 nucleotides downstream from EIIIB, and may represent a novel mode of exon regulation.

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[Phosphotyrosine]protein phosphatase in rat brain. A major [phosphotyrosine]protein phosphatase is a 23 kDa protein distinct from acid phosphatase

Biochemical Journal ◽

10.1042/bj2390155 ◽

1986 ◽

Vol 239 (1) ◽

pp. 155-162 ◽

Cited By ~ 35

Author(s):

M Okada ◽

K Owada ◽

H Nakagawa

Keyword(s):

Acid Phosphatase ◽

Molecular Mass ◽

Rat Brain ◽

Column Chromatography ◽

Protein Phosphatase ◽

Specific Activity ◽

Deae Cellulose ◽

Sodium Vanadate ◽

Nitrophenyl Phosphate ◽

Phosphotyrosine Protein Phosphatase

A [phosphotyrosine]protein phosphatase (PTPPase) was purified almost to homogeneity from rat brain, with [32P]p130gag-fps, an oncogene product of Fujinami sarcoma virus, as substrate. The characteristics of the purified preparation of PTPPase were as follows: the enzyme was a monomer with a molecular mass of 23 kDa; its optimum pH was 5.0-5.5; its activity was not dependent on bivalent cations; its activity was strongly inhibited by sodium vanadate, but was not inhibited by ZnCl2, L(+)-tartrate or NaF; it catalysed the dephosphorylation of [32P]p130gag-fps, [[32P]Tyr]casein, p-nitrophenyl phosphate and L-phosphotyrosine, but did not hydrolyse [[32P]Ser]tubulin, L-phosphoserine, DL-phosphothreonine, 5′-AMP, 2′-AMP or beta-glycerophosphate significantly. During the purification, most of the PTPPase activity was recovered in distinct fractions from those of conventional low-molecular-mass acid phosphatase (APase), which was reported to be a major PTPPase [Chernoff & Li (1985) Arch. Biochem. Biophys. 240, 135-145], from DE-52 DEAE-cellulose column chromatography, and those two enzymes could be completely separated by Sephadex G-75 column chromatography. APase also showed PTPPase activity with [32P]p130gag-fps, but the specific activity was lower than that of PTPPase with molecular mass of 23 kDa, and it was not sensitive to sodium vanadate. These findings suggested that PTPPase (23 kDa) was the major and specific PTPPase in the cell.

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