Epigenetic regulation of gene expression by Drosophila Myb and E2F2-RBF via the Myb-MuvB/dREAM complex.
The Drosophila Myb oncoprotein, the E2F2 transcriptional repressor, and the RBF and Mip130/LIN-9 tumor suppressor proteins reside in a conserved Myb-MuvB (MMB)/dREAM complex. We now show that Myb is required in vivo for the expression of Polo kinase and components of the spindle assembly checkpoint (SAC). Surprisingly, the highly conserved DNA-binding domain was not essential for assembly of Myb into MMB/dREAM, for transcriptional regulation in vivo, or for rescue of Myb-null mutants to adult viability. E2F2, RBF, and Mip130/LIN-9 acted in opposition to Myb by repressing the expression of Polo and SAC genes in vivo. Remarkably, the absence of both Myb and Mip130, or of both Myb and E2F2, caused variegated expression in which high or low levels of Polo were stably inherited through successive cell divisions in imaginal wing discs. Restoration of Myb resulted in a uniformly high level of Polo expression similar to that seen in wild-type tissue, whereas restoration of Mip130 or E2F2 extinguished Polo expression. Our results demonstrate epigenetic regulation of gene expression by Myb, Mip130/LIN-9, and E2F2-RBF in vivo, and also provide an explanation for the ability of Mip130-null mutants to rescue the lethality of Myb-null mutants in vivo.
Wen
Hong
H
Department of Pathology and Department of Genetics, Stanford University, Stanford, CA 94305, USA.
Andrejka
Laura
L
Ashton
Jonathan
J
Karess
Roger
R
Lipsick
Joseph S
JS
D000818:Animals; D002352:Carrier Proteins / Q000235:genetics / Q000378:metabolism; D020169:Caspases / Q000378:metabolism; D018797:Cell Cycle Proteins / Q000235:genetics / Q000378:metabolism*; D029721:Drosophila Proteins / Q000235:genetics / Q000378:metabolism*; D004331:Drosophila melanogaster / Q000235:genetics*; D050703:E2F2 Transcription Factor / Q000235:genetics / Q000378:metabolism*; D044127:Epigenesis, Genetic; D049452:Green Fluorescent Proteins / Q000032:analysis / Q000235:genetics; D008938:Mitosis / Q000235:genetics; D009369:Neoplasms / Q000235:genetics; D017346:Protein Serine-Threonine Kinases / Q000235:genetics; D020598:Proto-Oncogene Proteins c-myb / Q000235:genetics / Q000378:metabolism*; D016160:Retinoblastoma Protein / Q000235:genetics / Q000378:metabolism*; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism*
D002352:Carrier Proteins; D018797:Cell Cycle Proteins; D029721:Drosophila Proteins; D050703:E2F2 Transcription Factor; C115434:E2f2 protein, Drosophila; C489655:Mip130 protein, Drosophila; C467519:Myb protein, Drosophila; D020598:Proto-Oncogene Proteins c-myb; C099965:Rbf protein, Drosophila; D016160:Retinoblastoma Protein; D014157:Transcription Factors; D049452:Green Fluorescent Proteins; C072004:polo protein, Drosophila; D017346:Protein Serine-Threonine Kinases; D020169:Caspases; C438246:STRICA protein, Drosophila