Mechanisms of Gene Transcription Across the Hedgehog Signaling Gradient.

Enhancer;Morphogen gradients;Gene regulation;Transcription factor binding sites;Gli/Ci;Molecular;Cellular and Developmental Biology;Science;Cellular and Molecular Biology

Ramos Serrano, Andrea IsabelDlugosz, Andrzej A. ;

University of Michigan

关键词: Enhancer;    Morphogen gradients;    Gene regulation;    Transcription factor binding sites;    Gli/Ci;    Molecular;    Cellular and Developmental Biology;    Science;    Cellular and Molecular Biology;   

Others  :  https://deepblue.lib.umich.edu/bitstream/handle/2027.42/110416/airamos_1.pdf?sequence=1&isAllowed=y

瑞士|英语

来源: The Illinois Digital Environment for Access to Learning and Scholarship

【 摘 要 】

The combinatorial binding of transcription factors to enhancers controls unique patterns of gene expression to establish cell fates and body plans. Enhancers regulated by the Hedgehog (Hh) signaling morphogen integrate inputs from the bifunctional transcription factor Ci to activate or repress the expression of target genes in response to Hh signaling. Despite the essential role played by this pathway during organogenesis, it is not clear how Hh/Ci-regulated enhancers control different transcriptional outputs in different developmental contexts. Here, I examined the role of Ci binding sites in four Hh-regulated enhancers of dpp, patched (ptc), stripe and wingless. Counterintuitively, high-affinity enhancers with consensus Ci binding motifs respond in more restricted domains, whereas low-affinity enhancers with Ci site variants respond more broadly to Hh signaling. To further study the relationship between Ci binding sites and enhancer function, I characterized the role of predicted binding motifs in newly identified enhancers in the ptc locus. This analysis doubled the number of known Hh/Ci-regulated enhancers in Drosophila, and revealed that the vast majority of these enhancers require sites that deviate from the optimal Ci site to respond to Hh in different contexts. To better understand how the Ci binding site composition of these enhancers produce specific transcriptional outputs in vivo, I measured the transcriptional output of isolated Ci site variants. Using synthetic Hh-regulated enhancers with defined inputs, I found that certain Ci binding motifs are regulated in a Hh/Ci-independent manner. These findings may explain previous unexpected results, and suggest that some Ci sites may be under complex selective pressures to balance inputs from activator Ci, repressor Ci, and other transcription factors with overlapping binding preferences. Competition for shared or partially overlapping binding sites might provide tissue-specificity to Hh signaling.