Calmodulin binds to p21(Cip1) and is involved in the regulation of its nuclear localization.
p21(Cip1), first described as an inhibitor of cyclin-dependent kinases, has recently been shown to have a function in the formation of cyclin D-Cdk4 complexes and in their nuclear translocation. The dual behavior of p21(Cip1) may be due to its association with other proteins. Different evidence presented here indicate an in vitro and in vivo interaction of p21(Cip1) with calmodulin: 1) purified p21(Cip1) is able to bind to calmodulin-Sepharose in a Ca(2+)-dependent manner, and this binding is inhibited by the calmodulin-binding domain of calmodulin-dependent kinase II; 2) both molecules coimmunoprecipitate when extracted from cellular lysates; and 3) colocalization of calmodulin and p21(Cip1) can be detected in vivo by electron microscopy immunogold analysis. The carboxyl-terminal domain of p21(Cip1) is responsible for the calmodulin interaction, since p21(145-164) peptide is also able to bind calmodulin and to compete with full-length p21(Cip1) for the calmodulin binding. Because treatment of cells with anti-calmodulin drugs decreases the nuclear accumulation of p21(Cip1), we hypothesize that calmodulin interaction with p21(Cip1) is important for p21(Cip1), and in consequence for cyclin D-Cdk4, translocation into the cell nucleus.
Taulés
M
M
Departament de Biologia Cel.lular i Anatomia Patològica, Institut d'Investigacions Biomèdiques August Pi i Sunyer (IDIBAPS), Facultat de Medicina, Universitat de Barcelona, 08036 Barcelona, Spain.
Rodríguez-Vilarrupla
A
A
Rius
E
E
Estanyol
J M
JM
Casanovas
O
O
Sacks
D B
DB
Pérez-Payá
E
E
Bachs
O
O
Agell
N
N
D000595:Amino Acid Sequence; D000818:Animals; D002147:Calmodulin / Q000378:metabolism*; D002460:Cell Line; D002467:Cell Nucleus / Q000378:metabolism*; D019938:Cyclin D1 / Q000378:metabolism; D051358:Cyclin-Dependent Kinase 4; D050759:Cyclin-Dependent Kinase Inhibitor p21; D018844:Cyclin-Dependent Kinases / Q000378:metabolism; D016213:Cyclins / Q000737:chemistry / Q000378:metabolism*; D004789:Enzyme Activation; D008854:Microscopy, Electron; D008969:Molecular Sequence Data; D010766:Phosphorylation; D011233:Precipitin Tests; D011485:Protein Binding; D011518:Proto-Oncogene Proteins; D051381:Rats; D013449:Sulfonamides / Q000494:pharmacology
D002147:Calmodulin; C493958:Cdkn1a protein, rat; D050759:Cyclin-Dependent Kinase Inhibitor p21; D016213:Cyclins; D011518:Proto-Oncogene Proteins; D013449:Sulfonamides; D019938:Cyclin D1; C040184:W 12; C033772:N-(4-aminobutyl)-5-chloro-2-naphthalenesulfonamide; C495903:Cdk4 protein, rat; D051358:Cyclin-Dependent Kinase 4; D018844:Cyclin-Dependent Kinases