DNA binding protein dbpA binds Cdk5 and inhibits its activity

• Published in: FEBS letters 1999-03, Vol.446 (2), p.343-350
• Main Authors: Moorthamer, Mark, Zumstein-Mecker, Sabine, Chaudhuri, Bhabatosh
• Format: Article
• Language: English
• Subjects: Animals; Baculoviridae; CDC2-CDC28 Kinases; Cdk, human cyclin dependent kinase; Cell Line; Cloning, Molecular; COS Cells; CSD, cold shock domain; Cyclin D; Cyclin dependant kinase 5; Cyclin-Dependent Kinase 2; Cyclin-Dependent Kinase 4; Cyclin-Dependent Kinase 5; Cyclin-Dependent Kinases - antagonists & inhibitors; Cyclin-Dependent Kinases - genetics; Cyclin-Dependent Kinases - metabolism; Cyclins; DBD, DNA binding domain; DEAD-box RNA Helicases; DNA binding protein A; DNA-Binding Proteins - genetics; DNA-Binding Proteins - metabolism; Enzyme Activation; Escherichia coli Proteins; Glutathione Transferase; GSH-Sepharose, glutathione Sepharose; GST, glutathione S-transferase; HeLa Cells; Histidine; Humans; Kinase inhibitor; p35, 35 kDa protein which activates Cdk5; PCR, polymerase chain reaction; pRb, human retinoblastoma protein; Protein-Serine-Threonine Kinases - metabolism; Proto-Oncogene Proteins; Recombinant Fusion Proteins - genetics; Recombinant Fusion Proteins - metabolism; RNA Helicases - genetics; RNA Helicases - metabolism; RNA-Binding Proteins; RT, room temperature; SDS-PAGE, sodium dodecyl sulfate-polyacrylamide gel electrophoresis; Spodoptera; TAD, transcriptional activation domain; Yeast two-hybrid system; Yeasts; β-gal, β-galactosidase
• ISSN: 0014-5793; 1873-3468
• DOI: 10.1016/S0014-5793(99)00248-3

Progress in the cell cycle is governed by the activity of cyclin dependent kinases (Cdks). Unlike other Cdks, the Cdk5 catalytic subunit is found mostly in differentiated neurons. Interestingly, the only known protein that activates Cdk5 (i.e. p35) is expressed solely in the brain. It has been suggested that, besides its requirement in neuronal differentiation, Cdk5 activity is induced during myogenesis. However, it is not clear how this activity is regulated in the pathway that leads proliferative cells to differentiation. In order to find if there exists any Cdk5-interacting protein, the yeast two-hybrid system was used to screen a HeLa cDNA library. We have determined that a C-terminal 172 amino acid domain of the DNA binding protein, dbpA, binds to Cdk5. Biochemical analyses reveal that this fragment (dbpA(CΔ)) strongly inhibits p35-activated Cdk5 kinase. The protein also interacts with Cdk4 and inhibits the Cdk4/cyclin D1 enzyme. Surprisingly, dbpA(CΔ) does not bind Cdk2 in the two-hybrid assay nor does it inhibit Cdk2 activated by cyclin A. It could be that dbpA's ability to inhibit Cdk5 and Cdk4 reflects an apparent cross-talk between distinct signal transduction pathways controlled by dbpA on the one hand and Cdk5 or Cdk4 on the other.