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Hyperphosphorylation of N‐60, a protein structurally and immunologically related to nucleolin after tumour‐promoter treatment.
Author(s) -
Issinger O. G.,
Martin T.,
Richter W. W.,
Olson M.,
Fujiki H.
Publication year - 1988
Publication title -
the embo journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 7.484
H-Index - 392
eISSN - 1460-2075
pISSN - 0261-4189
DOI - 10.1002/j.1460-2075.1988.tb02988.x
Subject(s) - nucleolin , humanities , biology , library science , philosophy , genetics , computer science , cytoplasm , nucleolus
Okadaic acid, a non‐TPA‐type tumour promoter, induces hyperphosphorylation of a 60‐kd protein in primary human fibroblasts. Treatment with TPA‐type tumour promoters (e.g. TPA and teleocidin) did not cause this hyperphosphorylation. Phosphorylation of this protein was not seen at times earlier than 90 min after the addition of 75 ng/ml okadaic acid to the proliferating cell cultures. The presence of inhibitors such as actinomycin D and cycloheximide, did not significantly influence the level of hyperphosphorylation induced by okadaic acid treatment. By immunoblotting using an antibody anti‐nucleolin, the 60‐kd protein was identified as a fragment of nucleolar protein, nucleolin. Similarly, antibodies against the 60‐kd protein cross‐reacted with nucleolin. Furthermore peptide mapping, using staphylococcal V8 protease, showed that the 60‐kd protein phosphorylated by casein kinase II in vitro and the okadaic‐acid‐induced hyperphosphorylated 60‐kd protein exhibited identical phosphopeptide maps, indicating that there is also structural relatedness between N‐60 and nucleolin. Hyperphosphorylation of the nucleolin fragment (N‐60) was suppressed by anti‐tumour promoter retinoic acid.