Normal regulation of Rbf1/E2f1 target genes in Drosophila type 1 protein phosphatase mutants.
G1 Cyclin/Cdk complexes phosphorylate and inactivate the pRb tumor suppressor by preventing its ability to bind and repress E2F transcription factors. Current molecular and biochemical evidence suggests that type 1 protein phosphatases (PP1) dephosphorylate and thereby activate pRb, but the functional significance of this has not been addressed in the context of animal development. Here, we use genetic analyses to determine the role of PP1 in the regulation of Rbf1 activity during Drosophila development. While Rbf1 is required for E2f1 inhibition and G1 arrest in the embryonic epidermis and for the periodic expression of E2f1 target genes during endocycle S phase in the embryonic midgut and larval salivary gland, PP1 is not. PP1 regulates periodic cyclin E protein accumulation in ovarian nurse cells independently of Rbf1, which is dispensable for endocycle regulation in this tissue. We conclude that PP1 is not a major regulator of the Rbf1/E2F1 pathway in Drosophila.
Department of Biology, University of North Carolina, Chapel Hill, North Carolina 27599, USA.
Lisa M
LM
Swanhart
Akeisha N
AN
Sanders
Robert J
RJ
Duronio
D000818:Animals; D002384:Catalysis; D002453:Cell Cycle; D019927:Cyclin E / Q000096:biosynthesis / Q000378:metabolism; D029721:Drosophila Proteins / Q000378:metabolism*; D004331:Drosophila melanogaster / Q000235:genetics* / Q000378:metabolism*; D050687:E2F1 Transcription Factor / Q000378:metabolism*; D004817:Epidermis / Q000196:embryology; D018507:Gene Expression Regulation, Developmental; D015971:Gene Expression Regulation, Enzymologic; D017403:In Situ Hybridization; D009154:Mutation; D054645:Protein Phosphatase 1 / Q000235:genetics* / Q000502:physiology; D016160:Retinoblastoma Protein / Q000378:metabolism; D014157:Transcription Factors / Q000378:metabolism*; D019076:Transgenes
D019927:Cyclin E; D029721:Drosophila Proteins; D050687:E2F1 Transcription Factor; C099965:Rbf protein, Drosophila; D016160:Retinoblastoma Protein; D014157:Transcription Factors; D054645:Protein Phosphatase 1