Distribution of GAGA protein on Drosophila genes in vivo.
GAGA protein binds specific CT.GA-rich DNA sequences in vitro, and many of these sequences are required for transcription in vivo. GAGA protein has been implicated in the transcription of numerous Drosophila genes, including hsp70, hsp26, actin 5C, and Ubx. Here, we examine the in vivo distribution of GAGA protein on a number of Drosophila genes that do and do not have CT-rich sequences by use of a UV cross-linking technique. Prior to heat shock, GAGA protein is associated with the promoter regions of the uninduced hsp70 and hsp26 genes. Upon heat shock induction, GAGA protein is recruited to their transcription units with its distribution coincident with that of RNA polymerase II. The recruitment of GAGA protein to the hsp70 gene after an instantaneous heat shock occurs in a 5' to 3' manner with kinetics similar to RNA polymerase. GAGA protein has been shown to disrupt nucleosome both in vivo and in vitro. We propose that GAGA protein may function in vivo both by binding constitutively to its high-affinity binding sites and by spreading through the induced gene opening the chromatin structure allowing polymerase to elongate efficiently.
O'Brien
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Section of Biochemistry, Molecular and Cell Biology, Cornell University, Ithaca, New York 14853, USA.
Wilkins
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RC
Giardina
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Lis
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JT
D000199:Actins / Q000235:genetics; D000818:Animals; D001482:Base Composition; D004247:DNA / Q000378:metabolism*; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D004330:Drosophila / Q000235:genetics*; D029721:Drosophila Proteins; D005786:Gene Expression Regulation / Q000502:physiology; D017344:Genes, Insect; D018840:HSP70 Heat-Shock Proteins / Q000235:genetics; D006360:Heat-Shock Proteins / Q000235:genetics; D018398:Homeodomain Proteins; D008957:Models, Genetic; D011401:Promoter Regions, Genetic / Q000235:genetics; D012319:RNA Polymerase II / Q000378:metabolism; D011993:Recombinant Fusion Proteins / Q000096:biosynthesis / Q000276:immunology; D014157:Transcription Factors / Q000378:metabolism*; D014158:Transcription, Genetic / Q000502:physiology*; D014466:Ultraviolet Rays
D000199:Actins; D004268:DNA-Binding Proteins; D029721:Drosophila Proteins; D018840:HSP70 Heat-Shock Proteins; D006360:Heat-Shock Proteins; D018398:Homeodomain Proteins; C087442:Hsp26 protein, Drosophila; D011993:Recombinant Fusion Proteins; D014157:Transcription Factors; C063460:Trl protein, Drosophila; C066177:Ubx protein, Drosophila; D004247:DNA; D012319:RNA Polymerase II