Open AccessAttenuation of ribosomal protein S6 phosphatase activity in chicken embryo fibroblasts transformed by Rous sarcoma virus.
Author(s) -
Borja Belandia,
David L. Brautigan,
Jorge Martı́n-Pérez
Publication year - 1994
Publication title -
molecular and cellular biology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.14
H-Index - 327
eISSN - 1067-8824
pISSN - 0270-7306
DOI - 10.1128/mcb.14.1.200
Subject(s) - biology , rous sarcoma virus , phosphatase , ribosomal protein s6 , microbiology and biotechnology , phosphorylation , mitosis , immunoprecipitation , transformation (genetics) , neoplastic transformation , biochemistry , virus , virology , protein phosphorylation , gene , carcinogenesis , protein kinase a
In chicken embryo fibroblasts, phosphorylation of the 40S ribosomal protein S6 increases during G1 but returns to basal level by mitosis. In contrast, in Rous sarcoma virus (RSV)-transformed fibroblasts, S6 remains highly phosphorylated throughout mitosis. This study investigated the mechanism by which RSV alters the pattern of S6 phosphorylation. Pulse-chase experiments demonstrate that phosphate turnover in S6 is rapid in normal cells and in cells infected with an RSV transformation-defective virus. In contrast, phosphate turnover in S6 is severely reduced in cells infected with temperature-sensitive RSV at a temperature permissive for transformation, indicating a diminished S6 phosphatase activity. Fractionation of cell lysates by DEAE chromatography showed an almost threefold lower S6 phosphatase activity in RSV-transformed versus normal cells. The S6 phosphatase was sensitive to inhibitor 2 and specifically recognized by an antibody to type 1 phosphatase (PP1). The S6 phosphatase activity recovered by immunoprecipitation of PP1 was threefold lower in transformed cells, but the steady-state level of expression and the rate of synthesis of PP1 were not altered by oncogenic transformation. Together, the results show that transformation by RSV reduced the S6-PP1 activity.This research was supported by grants from DGICYT (PM89-0017 and PB92-0116), CAM (C263/91), and NATO (0010/89) to J.M.-P. and PHS grant DK-31374 to D.L.B. B.B. was supported by a fellowship from the Gobierno Vasco.Peer Reviewe