title: A novel E2 box-GATA element modulates Cdc6 transcription during human cells polyploidization.
abstract: Cdc6 is a key regulator of the strict alternation of S and M phases during the mitotic cell cycle. In mammalian and plant cells that physiologically become polyploid, cdc6 is transcriptionally and post-translationally regulated. We have recently reported that Cdc6 levels are maintained in megakaryoblastic HEL cells, but severely downregulated by ectopic expression of transcriptional repressor Drosophila melanogaster escargot. Here, we show that cdc6 promoter activity is upregulated during megakaryocytic differentiation of HEL endoreplicating cells, and that Escargot interferes with such activation. Transactivation experiments showed that a 1.7 kb region located at 2800 upstream cdc6 transcription initiation site behaved as a potent enhancer in endoreplicating cells only. This activity was mainly dependent on a novel cis-regulatory element composed by an E2 box overlapping a GATA motif. Ectopic Escargot could bind this regulatory element in vitro and endogenous GATA-1 and E2A formed specific complexes in megakaryoblastic cells as well as in primary megakaryocytes. Chromatin Immunoprecipitation analysis revealed that both transcription factors were occupying the E2 box/GATA site in vivo. Altogether, these data suggest that cdc6 expression could be actively maintained during megakaryocytic differentiation through transcriptional mechanisms involving specific cis- and trans-regulatory elements.
authors.affiliation: Department of Biochemistry, Instituto de Investigaciones Biomédicas A. Sols, Universidad Autónoma-CSIC, Arturo Duperier, 4, 28029 Madrid, Spain.
authors.forename: Nuria
authors.initials: N
authors.lastname: Vilaboa
authors.forename: Rodrigo
authors.initials: R
authors.lastname: Bermejo
authors.forename: Pilar
authors.initials: P
authors.lastname: Martinez
authors.forename: Rafael
authors.initials: R
authors.lastname: Bornstein
authors.forename: Carmela
authors.initials: C
authors.lastname: Calés
mesh_terms: D024506:5' Flanking Region; D000818:Animals; D051792:Basic Helix-Loop-Helix Proteins; D001665:Binding Sites; D018797:Cell Cycle Proteins / Q000096:biosynthesis / Q000235:genetics*; D002460:Cell Line; D004261:DNA Replication; D004268:DNA-Binding Proteins / Q000378:metabolism; D015536:Down-Regulation; D029721:Drosophila Proteins / Q000378:metabolism; D024721:E-Box Elements; D050981:Erythroid-Specific DNA-Binding Factors; D050982:GATA1 Transcription Factor; D005786:Gene Expression Regulation; D006801:Humans; D008533:Megakaryocytes / Q000378:metabolism*; D051379:Mice; D009687:Nuclear Proteins / Q000096:biosynthesis / Q000235:genetics*; D011123:Polyploidy; D012333:RNA, Messenger / Q000378:metabolism; D051381:Rats; D020218:Response Elements; D014157:Transcription Factors / Q000378:metabolism; D014158:Transcription, Genetic; D015533:Transcriptional Activation
chemical_list: D051792:Basic Helix-Loop-Helix Proteins; D018797:Cell Cycle Proteins; D004268:DNA-Binding Proteins; D029721:Drosophila Proteins; D050981:Erythroid-Specific DNA-Binding Factors; D050982:GATA1 Transcription Factor; D009687:Nuclear Proteins; D012333:RNA, Messenger; D014157:Transcription Factors; C103706:CDC6 protein, human; C494688:GATA1 protein, human; C494689:Gata1 protein, mouse; C494690:Gata1 protein, rat; C407909:TCF3 protein, human; C467520:esg protein, Drosophila