title: Preferences for phosphorylation sites in the retinoblastoma protein of D-type cyclin-dependent kinases, Cdk4 and Cdk6, in vitro.
abstract: D-type cyclin-dependent kinases (Cdk4 and Cdk6) regulate the G1 to S phase progression of the mammalian cell cycle. It has been suggested that Cdk4 and Cdk6 may have distinct functions in vivo, even though they are indistinguishable biochemically. Here we show that although these Cdks phosphorylate multiple residues in pRB, they do so with different residue selectivities in vitro; Thr821 and Thr826 are preferentially phosphorylated by Cdk6 and Cdk4, respectively. This raises the possibility different substrate specificities lead to their different roles in the regulation of cellular events. Furthermore, our results indicate the new concept that Cdk itself contributes to substrate recognition.
authors.affiliation: Banyu Tsukuba Research Institute in collaboration with Merck Research Laboratories, 3 Okubo, Tsukuba, Ibaraki 300-2611.
authors.forename: Tohru
authors.initials: T
authors.lastname: Takaki
authors.forename: Kazuhiro
authors.initials: K
authors.lastname: Fukasawa
authors.forename: Ikuko
authors.initials: I
authors.lastname: Suzuki-Takahashi
authors.forename: Kentaro
authors.initials: K
authors.lastname: Semba
authors.forename: Masatoshi
authors.initials: M
authors.lastname: Kitagawa
authors.forename: Yoichi
authors.initials: Y
authors.lastname: Taya
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Hirai
mesh_terms: D020816:Amino Acid Motifs; D015153:Blotting, Western; D051358:Cyclin-Dependent Kinase 4; D051361:Cyclin-Dependent Kinase 6; D018844:Cyclin-Dependent Kinases / Q000378:metabolism*; D004591:Electrophoresis, Polyacrylamide Gel; D010449:Peptide Mapping; D010748:Phosphopeptides / Q000737:chemistry; D010766:Phosphorylation; D011518:Proto-Oncogene Proteins / Q000378:metabolism*; D016160:Retinoblastoma Protein / Q000737:chemistry / Q000378:metabolism*; D013379:Substrate Specificity; D013912:Threonine / Q000378:metabolism
chemical_list: D010748:Phosphopeptides; D011518:Proto-Oncogene Proteins; D016160:Retinoblastoma Protein; D013912:Threonine; D051358:Cyclin-Dependent Kinase 4; D051361:Cyclin-Dependent Kinase 6; D018844:Cyclin-Dependent Kinases