title: c-Myb contributes to G2/M cell cycle transition in human hematopoietic cells by direct regulation of cyclin B1 expression.
abstract: Myb family proteins are ubiquitously expressed transcription factors. In mammalian cells, they play a critical role in regulating the G(1)/S cell cycle transition but their role in regulating other cell cycle checkpoints is incompletely defined. Herein, we report experiments which demonstrate that c-Myb upregulates cyclin B1 expression in normal and malignant human hematopoietic cells. As a result, it contributes directly to G(2)/M cell cycle progression. In cell lines and primary cells, cyclin B1 levels varied directly with c-Myb expression. Chromatin immunoprecipitation assays, mutation analysis, and luciferase reporter assays revealed that c-Myb bound the cyclin B1 promoter preferentially at a site just downstream of the transcriptional start site. The biological significance of c-Myb, versus B-Myb, binding the cyclin B1 promoter was demonstrated by the fact that expression of inducible dominant negative c-Myb in K562 cells accelerated their exit from M phase. In addition, expression of c-Myb in HCT116 cells rescued cyclin B1 expression after B-myb expression was silenced with small interfering RNA. These results suggest that c-Myb protein plays a previously unappreciated role in the G(2)/M cell cycle transition of normal and malignant human hematopoietic cells and expands the known repertoire of c-myb functions in regulating human hematopoiesis.
authors.affiliation: Division of Hematology/Oncology, Department of Medicine, University of Pennsylvania School of Medicine, Philadelphia, PA 19104, USA.
authors.forename: Yuji
authors.initials: Y
authors.lastname: Nakata
authors.forename: Susan
authors.initials: S
authors.lastname: Shetzline
authors.forename: Chizuko
authors.initials: C
authors.lastname: Sakashita
authors.forename: Anna
authors.initials: A
authors.lastname: Kalota
authors.forename: Ravikumar
authors.initials: R
authors.lastname: Rallapalli
authors.forename: Stephen I
authors.initials: SI
authors.lastname: Rudnick
authors.forename: Yi
authors.initials: Y
authors.lastname: Zhang
authors.forename: Stephen G
authors.initials: SG
authors.lastname: Emerson
authors.forename: Alan M
authors.initials: AM
authors.lastname: Gewirtz
mesh_terms: D018952:Antigens, CD34 / Q000378:metabolism; D001483:Base Sequence; D002455:Cell Division; D002478:Cells, Cultured; D019926:Cyclin B / Q000235:genetics / Q000378:metabolism*; D056744:Cyclin B1; D016195:G2 Phase; D005786:Gene Expression Regulation / Q000187:drug effects; D006413:Hematopoietic System; D006801:Humans; D007376:Interleukin-2 / Q000494:pharmacology; D010835:Phytohemagglutinins / Q000494:pharmacology; D020598:Proto-Oncogene Proteins c-myb / Q000235:genetics / Q000378:metabolism; D034741:RNA, Small Interfering / Q000235:genetics; D013601:T-Lymphocytes / Q000187:drug effects / Q000378:metabolism
chemical_list: D018952:Antigens, CD34; C534699:CCNB1 protein, human; D019926:Cyclin B; D056744:Cyclin B1; D007376:Interleukin-2; D010835:Phytohemagglutinins; D020598:Proto-Oncogene Proteins c-myb; D034741:RNA, Small Interfering