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The mcp element from the Drosophila melanogaster bithorax complex mediates long-distance regulatory interactions
M Muller1, K Hagstrom, H Gyurkovics
1Department of Molecular Biology, Princeton University, Princeton, New Jersey 08540, USA.
Abstract:
In the studies reported here, we have examined the properties of the Mcp element from the Drosophila melanogaster bithorax complex (BX-C). We have found that sequences from the Mcp region of BX-C have properties characteristic of Polycomb response elements (PREs), and that they silence adjacent reporters by a mechanism that requires trans-interactions between two copies of the transgene. However, Mcp trans-regulatory interactions have several novel features. In contrast to classical transvection, homolog pairing does not seem to be required. Thus, trans-regulatory interactions can be observed not only between Mcp transgenes inserted at the same site, but also between Mcp transgenes inserted at distant sites on the same chromosomal arm, or even on different arms. Trans-regulation can even be observed between transgenes inserted on different chromosomes. A small 800-bp Mcp sequence is sufficient to mediate these long-distance trans-regulatory interactions. This small fragment has little silencing activity on its own and must be combined with other Polycomb-Group-responsive elements to function as a "pairing-sensitive" silencer. Finally, this pairing element can also mediate long-distance interactions between enhancers and promoters, activating mini-white expression.
Insights
The Mcp element from Drosophila melanogaster
Area of Science:
- Developmental Biology
- Genetics
- Molecular Biology
Background:
- The bithorax complex (BX-C) in Drosophila melanogaster is crucial for embryonic development.
- Polycomb group (PcG) proteins maintain cellular memory by silencing genes.
- Polycomb response elements (PREs) are DNA sequences that recruit PcG proteins.
Purpose of the Study:
- To investigate the properties of the Mcp element from the Drosophila melanogaster bithorax complex (BX-C).
- To determine the mechanism by which Mcp mediates gene silencing and trans-regulatory interactions.
- To explore the potential of Mcp in mediating long-distance enhancer-promoter interactions.
Main Methods:
- Transgenic Drosophila melanogaster lines were generated with Mcp sequences driving reporter genes.
- Gene silencing assays were performed to assess the function of Mcp.
- Analysis of trans-interactions between Mcp transgenes at various genomic locations.
Main Results:
- Mcp sequences function as Polycomb response elements (PREs), silencing adjacent reporters via trans-interactions.
- Homolog pairing is not required for Mcp-mediated trans-regulatory interactions.
- An 800-bp Mcp fragment mediates long-distance trans-regulation, including enhancer-promoter interactions, and requires other PREs for robust silencing.
Conclusions:
- The Mcp element exhibits unique long-distance trans-regulatory properties distinct from classical transvection.
- Mcp can mediate interactions between transgenes irrespective of their genomic location, including on different chromosomes.
- Mcp plays a role in both gene silencing and enhancer-promoter communication, highlighting its complex regulatory functions in Drosophila development.