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We have previously shown that poly(A) polymerase (PAP) is negatively regulated by cyclin B-cdc2 kinase hyperphosphorylation in the M phase of the cell cycle. Here we show that cyclin B(1) binds PAP directly, and we demonstrate further that this interaction is mediated by a stretch of amino acids in PAP with homology to the cyclin recognition motif (CRM), a sequence previously shown in several cell cycle regulators to target specifically G(1)-phase-type cyclins. We find that PAP interacts with not only G(1)- but also G(2)-type cyclins via the CRM and is a substrate for phosphorylation by both types of cyclin-cdk pairs. PAP's CRM shows novel, concentration-dependent effects when introduced as an 8-mer peptide into binding and kinase assays. While higher concentrations of PAP's CRM block PAP-cyclin binding and phosphorylation, lower concentrations induce dramatic stimulation of both activities. Our data not only support the notion that PAP is directly regulated by cyclin-dependent kinases throughout the cell cycle but also introduce a novel type of CRM that functionally interacts with both G(1)- and G(2)-type cyclins in an unexpected way.

Original publication

DOI

10.1128/mcb.20.14.5310-5320.2000

Type

Journal article

Journal

Mol Cell Biol

Publication Date

07/2000

Volume

20

Pages

5310 - 5320

Keywords

Amino Acid Motifs, Animals, CDC2 Protein Kinase, Cells, Cultured, Cyclin-Dependent Kinases, Cyclins, G1 Phase, G2 Phase, Peptide Fragments, Phosphorylation, Polynucleotide Adenylyltransferase