title: B-Myb promotes S-phase independently of its sequence-specific DNA binding activity and interacts with polymerase delta-interacting protein 1 (Pdip1).
abstract: B-Myb is a highly conserved member of the Myb transcription factor family, which plays an essential role in cell cycle progression by regulating the transcription of genes at the G 2/M-phase boundary. The role of B-Myb in other parts of the cell cycle is less well-understood. By employing siRNA-mediated silencing of B-Myb expression, we found that B-Myb is required for efficient entry into S-phase. Surprisingly, a B-Myb mutant that lacks sequence-specific DNA-binding activity and is unable to activate transcription of B-Myb target genes is able to rescue the S-phase defect observed after B-Myb knockdown. Moreover, we have identified polymerase delta-interacting protein 1 (Pdip1), a BTB domain protein known to bind to the DNA replication and repair factor PCNA as a novel B-Myb interaction partner. We have shown that Pdip1 is able to interact with B-Myb and PCNA simultaneously. In addition, we found that a fraction of endogenous B-Myb can be co-precipitated via PCNA, suggesting that B-Myb might be involved in processes related to DNA replication or repair. Taken together, our work suggests a novel role for B-Myb in S-phase that appears to be independent of its sequence-specific DNA-binding activity and its ability to stimulate the expression of bona fide B-Myb target genes.
authors.affiliation: Institut für Biochemie, Westfälische-Wilhelms-Universität Münster, Münster, Germany.
authors.forename: Eugen
authors.initials: E
authors.lastname: Werwein
authors.forename: Thore
authors.initials: T
authors.lastname: Schmedt
authors.forename: Heiko
authors.initials: H
authors.lastname: Hoffmann
authors.forename: Clemens
authors.initials: C
authors.lastname: Usadel
authors.forename: Nora
authors.initials: N
authors.lastname: Obermann
authors.forename: Jeffrey D
authors.initials: JD
authors.lastname: Singer
authors.forename: Karl-Heinz
authors.initials: KH
authors.lastname: Klempnauer
mesh_terms: D000818:Animals; D018797:Cell Cycle Proteins / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D002460:Cell Line; D002645:Chickens; D004247:DNA / Q000737:chemistry / Q000378:metabolism*; D004261:DNA Replication; D057809:HEK293 Cells; D056945:Hep G2 Cells; D006801:Humans; D009154:Mutation; D009687:Nuclear Proteins / Q000378:metabolism*; D018809:Proliferating Cell Nuclear Antigen / Q000378:metabolism; D011485:Protein Binding; D034622:RNA Interference; D034741:RNA, Small Interfering / Q000378:metabolism; D059807:S Phase Cell Cycle Checkpoints; D015534:Trans-Activators / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D014162:Transfection
chemical_list: D018797:Cell Cycle Proteins; C439978:KCTD13 protein, human; C064352:MYBL2 protein, human; D009687:Nuclear Proteins; D018809:Proliferating Cell Nuclear Antigen; D034741:RNA, Small Interfering; D015534:Trans-Activators; D004247:DNA