Researchers found a mechanism which is critical for the initiation of embryonic development

Biologists from New York University and scientists at the Stowers Institute for Medical Research have just found a mechanism that promotes activation of genes critical for the initiation of embryonic development.
The paper was published in the journal Genome Research. Christine Rushlow, a professor of biology at NYU, and Julia Zeitlinger, a principal investigator at Kansas City's Stowers Institute, are co-authors of the paper. According to them, our genes are activated by regulatory factors that bind to the control regions of genes called "enhancers"—a process necessary to turn them on at the right time during development. Scientists are so interested in how they gain access to the enhancer regions when they are wrapped in proteins that form the chromosome structure.
They find that a protein called Zelda in the fruit fly embryo is responsible for "opening up" the enhancer regions so that other regulatory factors can gain access and bind to them, thus enabling activation of the associated genes. They also find that enhancer regions appear to be inherently "closed". That's to say, they like to be wrapped in proteins, more so than other non-enhancer regions of the genome, and Zelda tackles the regions to open them up.
"It makes sense that enhancers are intrinsically closed because you do not want developmental genes to turn on inadvertently," says Rushlow, part of NYU's Center for Developmental Genetics. "Instead, it is important that they are tightly controlled so they are active only at the right time and right place. Otherwise, tissue and organs could end up in the wrong place or not form at all."
"We suspect that the more these enhancers are intrinsically closed, the better they can be regulated," says Zeitlinger, who is also an assistant professor at the University of Kansas Medical Center. "It may be counterintuitive, but the tight enclosure allows Zelda to open these enhancer regions just enough for other more tissue-specific factors to come in without risking the enhancers becoming active at the wrong time or place."
Zelda allows many different factors to gain access, thus helping them establish the different tissues of the embryo. The results demonstrate the significance of a mechanism that scouts out enhancers across the genome to prime them for later activation by tissue-specific factors. When Zelda was absent, the binding of other factors such as the Dorsal protein, which is important for proper dorsal-ventral (back-belly) patterning of the fly body, was greatly reduced at target enhancers, and instead redistributed to other regions of the genome that are inherently open.
The findings point out a new-found and critical role of this protein.
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