title: Two E2F elements regulate the proliferating cell nuclear antigen promoter differently during leaf development.
abstract: E2F transcription factors regulate genes expressed at the G1/S boundary of the cell division cycle in higher eukaryotes. Although animal E2F proteins and their target promoters have been studied extensively, little is known about how these factors regulate plant promoters. An earlier study identified two E2F consensus binding sites in the promoter of a Nicotiana benthamiana gene encoding proliferating cell nuclear antigen (PCNA) and showed that the proximal element (E2F2) is required for the full repression of PCNA expression in mature leaves. In this study, we examined the distal element (E2F1) and how it interacts with the E2F2 site to regulate the PCNA promoter. Gel shift assays using plant nuclear extracts or purified Arabidopsis E2F and DP proteins showed that different complexes bind to the two E2F sites. Mutation of the E2F1 site or both sites differentially altered PCNA promoter function in transgenic plants. As reported previously for the E2F2 mutation, the E2F1 and E2F1+2 mutations partially relieved the repression of the PCNA promoter in mature leaves. In young tissues, the E2F1 mutation resulted in a threefold reduction in PCNA promoter activity, whereas the E2F1+2 mutation had no detectable effect. The activity of E2F1+2 mutants was indistinguishable from that of E2F2 mutants. These results demonstrate that both E2F elements contribute to the repression of the PCNA promoter in mature leaves, whereas the E2F1 site counters the repression activity of the E2F2 element in young leaves.
authors.affiliation: Department of Biochemistry, North Carolina State University, Raleigh, North Carolina 27695, USA.
authors.forename: Erin M
authors.initials: EM
authors.lastname: Egelkrout
authors.forename: Luisa
authors.initials: L
authors.lastname: Mariconti
authors.forename: Sharon B
authors.initials: SB
authors.lastname: Settlage
authors.forename: Rino
authors.initials: R
authors.lastname: Cella
authors.forename: Dominique
authors.initials: D
authors.lastname: Robertson
authors.forename: Linda
authors.initials: L
authors.lastname: Hanley-Bowdoin
mesh_terms: D001483:Base Sequence; D001665:Binding Sites / Q000235:genetics; D018797:Cell Cycle Proteins; D004268:DNA-Binding Proteins; D050684:E2F Transcription Factors; D050687:E2F1 Transcription Factor; D017791:Geminiviridae / Q000235:genetics / Q000502:physiology; D018507:Gene Expression Regulation, Developmental; D018506:Gene Expression Regulation, Plant; D008969:Molecular Sequence Data; D009154:Mutation; D018515:Plant Leaves / Q000235:genetics* / Q000254:growth & development / Q000821:virology; D030821:Plants, Genetically Modified; D018809:Proliferating Cell Nuclear Antigen / Q000235:genetics* / Q000378:metabolism; D011401:Promoter Regions, Genetic / Q000235:genetics*; D011485:Protein Binding; D020218:Response Elements / Q000235:genetics; D014026:Nicotiana / Q000235:genetics / Q000254:growth & development / Q000821:virology; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism
chemical_list: D018797:Cell Cycle Proteins; D004268:DNA-Binding Proteins; D050684:E2F Transcription Factors; D050687:E2F1 Transcription Factor; D018809:Proliferating Cell Nuclear Antigen; D014157:Transcription Factors