Alkaline phosphatase and protein kinase(s) activities in free cytoplasmic mRNPs from human term placenta

H. Lorberboum; H. Galski; C. Scharf; D. Weinstein; N. de Groot; A. A. Hochberg

doi:10.1007/BF00417592

Alkaline phosphatase and protein kinase(s) activities in free cytoplasmic mRNPs from human term placenta

H. Lorberboum^*, H. Galski, C. Scharf, D. Weinstein, N. de Groot, A. A. Hochberg

^*Corresponding author for this work

Department of Biochemistry and Molecular Biology

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Abstract

Free mRNPs isolated from human term placental tissue were examined for protein kinase and phosphoprotein-phosphatase activities. Free mRNPs incubated with [γ-³²P]ATP in a protein kinase standard buffer show self-phosphorylation in the absence of exogenous substrates. Treatment of phosphorylated products with alkali showed a significant phosphorylation of tyrosine residues within the mRNP-proteins. An alkaline-phosphatase activity was found to be tightly associated with the mRNPs. Both heat stable and heat labile alkaline phosphatase activities were found in the mRNPs. Heat labile alkaline phosphatase is the major isoenzyme form of the mRNPs. The existence of both protein kinase(s) and alkaline phosphatase activities in placental free cytoplasmic mRNPs might suggest that a balance between phosphorylation, specifically on tyrosine residues, and dephosphorylation states of some of the mRNP-proteins is relevant for their physiological functions, and may therefore play a role in the regulation of mRNPs' metabolism and, consequently, in mRNA translation.

Original language	English
Pages (from-to)	29-35
Number of pages	7
Journal	Molecular Biology Reports
Volume	11
Issue number	1
DOIs	https://doi.org/10.1007/BF00417592
State	Published - Mar 1986

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title = "Alkaline phosphatase and protein kinase(s) activities in free cytoplasmic mRNPs from human term placenta",

abstract = "Free mRNPs isolated from human term placental tissue were examined for protein kinase and phosphoprotein-phosphatase activities. Free mRNPs incubated with [γ-32P]ATP in a protein kinase standard buffer show self-phosphorylation in the absence of exogenous substrates. Treatment of phosphorylated products with alkali showed a significant phosphorylation of tyrosine residues within the mRNP-proteins. An alkaline-phosphatase activity was found to be tightly associated with the mRNPs. Both heat stable and heat labile alkaline phosphatase activities were found in the mRNPs. Heat labile alkaline phosphatase is the major isoenzyme form of the mRNPs. The existence of both protein kinase(s) and alkaline phosphatase activities in placental free cytoplasmic mRNPs might suggest that a balance between phosphorylation, specifically on tyrosine residues, and dephosphorylation states of some of the mRNP-proteins is relevant for their physiological functions, and may therefore play a role in the regulation of mRNPs' metabolism and, consequently, in mRNA translation.",

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AU - Lorberboum, H.

AU - Galski, H.

AU - Scharf, C.

AU - Weinstein, D.

AU - de Groot, N.

AU - Hochberg, A. A.

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N2 - Free mRNPs isolated from human term placental tissue were examined for protein kinase and phosphoprotein-phosphatase activities. Free mRNPs incubated with [γ-32P]ATP in a protein kinase standard buffer show self-phosphorylation in the absence of exogenous substrates. Treatment of phosphorylated products with alkali showed a significant phosphorylation of tyrosine residues within the mRNP-proteins. An alkaline-phosphatase activity was found to be tightly associated with the mRNPs. Both heat stable and heat labile alkaline phosphatase activities were found in the mRNPs. Heat labile alkaline phosphatase is the major isoenzyme form of the mRNPs. The existence of both protein kinase(s) and alkaline phosphatase activities in placental free cytoplasmic mRNPs might suggest that a balance between phosphorylation, specifically on tyrosine residues, and dephosphorylation states of some of the mRNP-proteins is relevant for their physiological functions, and may therefore play a role in the regulation of mRNPs' metabolism and, consequently, in mRNA translation.

AB - Free mRNPs isolated from human term placental tissue were examined for protein kinase and phosphoprotein-phosphatase activities. Free mRNPs incubated with [γ-32P]ATP in a protein kinase standard buffer show self-phosphorylation in the absence of exogenous substrates. Treatment of phosphorylated products with alkali showed a significant phosphorylation of tyrosine residues within the mRNP-proteins. An alkaline-phosphatase activity was found to be tightly associated with the mRNPs. Both heat stable and heat labile alkaline phosphatase activities were found in the mRNPs. Heat labile alkaline phosphatase is the major isoenzyme form of the mRNPs. The existence of both protein kinase(s) and alkaline phosphatase activities in placental free cytoplasmic mRNPs might suggest that a balance between phosphorylation, specifically on tyrosine residues, and dephosphorylation states of some of the mRNP-proteins is relevant for their physiological functions, and may therefore play a role in the regulation of mRNPs' metabolism and, consequently, in mRNA translation.

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Alkaline phosphatase and protein kinase(s) activities in free cytoplasmic mRNPs from human term placenta

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