Midline enhancer activity of the short gastrulation shadow enhancer is characterized by three unusual features for cis-regulatory DNA.
The shadow enhancer of the short gastrulation (sog) gene directs its sequential expression in the neurogenic ectoderm and the ventral midline of the developing Drosophila embryo. Here, we characterize three unusual features of the shadow enhancer midline activity. First, the minimal regions for the two different enhancer activities exhibit high overlap within the shadow enhancer, meaning that one developmental enhancer possesses dual enhancer activities. Second, the midline enhancer activity relies on five Single-minded (Sim)-binding sites, two of which have not been found in any Sim target enhancers. Finally, two linked Dorsal (Dl)- and Zelda (Zld)-binding sites, critical for the neurogenic ectoderm enhancer activity, are also required for the midline enhancer activity. These results suggest that early activation by Dl and Zld may facilitate late activation via the noncanonical sites occupied by Sim. We discuss a model for Zld as a pioneer factor and speculate its role in midline enhancer activity.
Graduate School of East-West Medical Science, Kyung Hee University, Yongin 17104, Korea.
Dong-Hyeon
DH
Shin
Graduate School of East-West Medical Science, Kyung Hee University, Yongin 17104, Korea.
Joung-Woo
JW
Hong
D000818:Animals; D051792:Basic Helix-Loop-Helix Proteins / Q000235:genetics / Q000378:metabolism; D001665:Binding Sites; D004247:DNA / Q000235:genetics* / Q000378:metabolism; D004330:Drosophila; D029721:Drosophila Proteins / Q000235:genetics* / Q000378:metabolism; D004475:Ectoderm / Q000378:metabolism; D004742:Enhancer Elements, Genetic; D018507:Gene Expression Regulation, Developmental; D009687:Nuclear Proteins / Q000235:genetics / Q000378:metabolism; D011485:Protein Binding
D051792:Basic Helix-Loop-Helix Proteins; D004247:DNA; D029721:Drosophila Proteins; D009687:Nuclear Proteins; C089449:sim protein, Drosophila; C091428:sog protein, Drosophila