tailieunhanh - Báo cáo khoa học: Identification and characterization of B¢¢-subunits of protein phosphatase 2 A in Xenopus laevis oocytes and adult tissues Evidence for an independent N-terminal splice variant of PR130 and an extended human PR48 protein

Protein phosphatase 2A is a phosphoserine/threonine phosphatase implicated inmany cellular processes. The core enzyme comprises a catalytic and a PR65/A-subunit. The substrate specificity and subcellular localization are deter-mined by a third regulatory B-subunit (PR55/B, PR61/B¢ and PR72/130/B¢¢). To identify the proteins of the B¢¢family inXenopus laevisoocytes, aprophaseXenopusoocyte cDNA librarywas screened using humanPR130 cDNAas a probe. Three different classes of cDNAs were isolated | Eur. J. Biochem. 270 376-387 2003 FEBS 2003 doi Identification and characterization of B -subunits of protein phosphatase 2 A in Xenopus laevis oocytes and adult tissues Evidence for an independent N-terminal splice variant of PR130 and an extended human PR48 protein Ilse Stevens1 Veerle Janssens1 Ellen Martens1 Stephen Dilworth1 Jozef Goris1 and Christine Van Hoof1 1 Afdeling Biochemie Faculteit Geneeskunde Katholieke Universiteit Leuven Leuven Belgium 2Department of Metabolic Medicine Imperial College Faculty of Medicine Hammersmith Hospital London UK Protein phosphatase 2A is a phosphoserine threonine phosphatase implicated in many cellular processes. The core enzyme comprises a catalytic and a PR65 A-subunit. The substrate specificity and subcellular localization are determined by a third regulatory B-subunit PR55 B PR61 B and PR72 130 B . To identify the proteins of the B family in Xenopus laevis oocytes a prophase Xenopus oocyte cDNA library was screened using human PR130 cDNA as a probe. Three different classes of cDNAs were isolated. One class is very similar to human PR130 and is probably the Xenopus orthologue of PR130 XPR130 . A second class of clones XN73 is identical to the N-terminal part of XPR130 but ends a few amino acids downstream of the putative splicing site of PR130. To investigate how this occurs the genomic structure of the human PR130 gene was determined. This novel protein does not act as a PP2A subunit but might compete with the function of PR130. The third set of clones XPR70 is very similar to human PR48 but has an N-ter-minal extension. Further analysis of the human EST-data-base and the human PR48 gene structure revealed that the human PR48 clone published is incomplete. The Xenopus orthologue of PR48 encodes a protein of 70 kDa which like the XPR130 interacts with the A-subunit in GST pull-down assays. XPR70 is ubiquitously expressed in adult tissues and oocytes whereas expression of XPR130 is very .

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