Phosphorylation of the p34 subunit of human single-stranded-DNA-binding protein in cyclin A-activated G(1) extracts is catalyzed by cdk-cyclin A complex and DNA-dependent protein kinase Journal Article
| Authors: | Pan, Z. Q.; Amin, A. A.; Gibbs, E.; Niu, H.; Hurwitz, J. |
| Article Title: | Phosphorylation of the p34 subunit of human single-stranded-DNA-binding protein in cyclin A-activated G(1) extracts is catalyzed by cdk-cyclin A complex and DNA-dependent protein kinase |
| Abstract: | The human single-stranded-DNA-binding protein (HSSB, also called RP-A) is a trimeric complex (p70, p34, and p14) required for multiple functions in DNA transactions. We report here that the p34 subunit of HSSB was hyperphosphorylated by kinase activities present in G1 extract (obtained from HeLa cells in G1 phase) preincubated with human cyclin A. This hyperphosphorylated HSSB product included at least four species of p34 that migrated more slowly through denaturing polyacrylamide gels than the hypophosphorylated form. Fractionation of cyclin A-activated G1 extract identified two kinases involved in the hyperphosphorylation of HSSB p34; cdk- cyclin A complex and DNA-dependent p350 protein kinase (DNA-PK). Kinetic analysis revealed that in cyclin A-activated G1 extract, p34 was first phosphorylated by cdk-cyclin A prior to the action of DNA-PK. Addition of p21(cip 1), a specific inhibitor of cdk-cyclin A but not DNA-PK, nearly abolished the hyperphosphorylation of HSSB p34 in G1 extract preincubated with cyclin A. This suggests a requirement of the cdk-cyclin A activity for the phosphorylation of p34 by DNA-PK in G1 extract. |
| Keywords: | protein phosphorylation; human cell; dna replication; protein dna binding; enzyme activity; hela cell; monoclonal antibody; protein purification; immunoblotting; cyclin a; cell cycle regulation; protein kinase; cell cycle g1 phase; protein antibody; single stranded dna binding protein; human; priority journal; article; dna transactions |
| Journal Title: | Proceedings of the National Academy of Sciences of the United States of America |
| Volume: | 91 |
| Issue: | 18 |
| ISSN: | 0027-8424 |
| Publisher: | National Academy of Sciences |
| Date Published: | 1994-08-30 |
| Start Page: | 8343 |
| End Page: | 8347 |
| Language: | English |
| DOI: | 10.1073/pnas.91.18.8343 |
| PROVIDER: | scopus |
| PMCID: | PMC44602 |
| PUBMED: | 8078885 |
| DOI/URL: | |
| Notes: | Export Date: 14 January 2019 -- Article -- CODEN: PNASA C2 -- Source: Scopus |
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