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Distinct contributions of MSL complex subunits to the transcriptional enhancement responsible for dosage compensation in Drosophila.

Dunlap D, Yokoyama R, Ling H, Sun HY, McGill K, Cugusi S, Lucchesi JC - Nucleic Acids Res. (2012)

Bottom Line: In Drosophila, this mechanism, designed to compensate for the difference in the dosage of X-linked genes between the sexes, depends on the MSL complex that enhances the transcription of the single dose of these genes in males.We have determined that the association of the MSL complex reduces the level of negative supercoiling of the deoxyribonucleic acid of compensated genes, and we have defined the role that the other subunits of the complex play in this topological modification.Lastly, we have analyzed the potential contribution of ISWI-containing remodeling complexes to the architecture of compensated chromatin, and we suggest a role for this remodeling factor in dosage compensation.

View Article: PubMed Central - PubMed

Affiliation: Department of Cell Biology and Department of Biology, Emory University, Atlanta, GA 30322, USA.

ABSTRACT
The regulatory mechanism of dosage compensation is the paramount example of epigenetic regulation at the chromosomal level. In Drosophila, this mechanism, designed to compensate for the difference in the dosage of X-linked genes between the sexes, depends on the MSL complex that enhances the transcription of the single dose of these genes in males. We have investigated the function of various subunits of the complex in mediating dosage compensation. Our results confirm that the highly enriched specific acetylation of histone H4 at lysine 16 of compensated genes by the histone acetyl transferase subunit MOF induces a more disorganized state of their chromatin. We have determined that the association of the MSL complex reduces the level of negative supercoiling of the deoxyribonucleic acid of compensated genes, and we have defined the role that the other subunits of the complex play in this topological modification. Lastly, we have analyzed the potential contribution of ISWI-containing remodeling complexes to the architecture of compensated chromatin, and we suggest a role for this remodeling factor in dosage compensation.

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Dosage compensation was measured as the ratio of relative luciferase activity (firefly vsersus Renilla) between S2 cells transfected with plasmid bearing a roX site next to the firefly gene and S2 cells transfected with a plasmid lacking a roX site. In S2 cells treated with RNAi to GFP (mock) or ISWI, ISWI knockdown did not affect dosage compensation.
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gks890-F7: Dosage compensation was measured as the ratio of relative luciferase activity (firefly vsersus Renilla) between S2 cells transfected with plasmid bearing a roX site next to the firefly gene and S2 cells transfected with a plasmid lacking a roX site. In S2 cells treated with RNAi to GFP (mock) or ISWI, ISWI knockdown did not affect dosage compensation.

Mentions: The absence of an effect of ISWI knockdown on the change in template topology specifically associated with dosage-compensated genes led us to ask whether dosage compensation of the plasmids, as determined by the relative activity of the firefly luciferase reporter gene, remains unchanged. Firefly luciferase activity relative to Renilla luciferase activity was measured in cells in which the MSL complex forms and in cells in which it does not, in the presence or absence of ISWI RNA interference. The absence of ISWI leads to a substantial increase in the transcription of the firefly luciferase gene in both types of cells, whereas the Renilla luciferase gene exhibits only a minor enhancement in transcription (data not shown). Nevertheless, the results of these experiments show that the absence of ISWI has no effect on the dosage compensation of the firefly plasmid (Figure 7).Figure 7.


Distinct contributions of MSL complex subunits to the transcriptional enhancement responsible for dosage compensation in Drosophila.

Dunlap D, Yokoyama R, Ling H, Sun HY, McGill K, Cugusi S, Lucchesi JC - Nucleic Acids Res. (2012)

Dosage compensation was measured as the ratio of relative luciferase activity (firefly vsersus Renilla) between S2 cells transfected with plasmid bearing a roX site next to the firefly gene and S2 cells transfected with a plasmid lacking a roX site. In S2 cells treated with RNAi to GFP (mock) or ISWI, ISWI knockdown did not affect dosage compensation.
© Copyright Policy - creative-commons
Related In: Results  -  Collection

License 1 - License 2
Show All Figures
getmorefigures.php?uid=PMC3526317&req=5

gks890-F7: Dosage compensation was measured as the ratio of relative luciferase activity (firefly vsersus Renilla) between S2 cells transfected with plasmid bearing a roX site next to the firefly gene and S2 cells transfected with a plasmid lacking a roX site. In S2 cells treated with RNAi to GFP (mock) or ISWI, ISWI knockdown did not affect dosage compensation.
Mentions: The absence of an effect of ISWI knockdown on the change in template topology specifically associated with dosage-compensated genes led us to ask whether dosage compensation of the plasmids, as determined by the relative activity of the firefly luciferase reporter gene, remains unchanged. Firefly luciferase activity relative to Renilla luciferase activity was measured in cells in which the MSL complex forms and in cells in which it does not, in the presence or absence of ISWI RNA interference. The absence of ISWI leads to a substantial increase in the transcription of the firefly luciferase gene in both types of cells, whereas the Renilla luciferase gene exhibits only a minor enhancement in transcription (data not shown). Nevertheless, the results of these experiments show that the absence of ISWI has no effect on the dosage compensation of the firefly plasmid (Figure 7).Figure 7.

Bottom Line: In Drosophila, this mechanism, designed to compensate for the difference in the dosage of X-linked genes between the sexes, depends on the MSL complex that enhances the transcription of the single dose of these genes in males.We have determined that the association of the MSL complex reduces the level of negative supercoiling of the deoxyribonucleic acid of compensated genes, and we have defined the role that the other subunits of the complex play in this topological modification.Lastly, we have analyzed the potential contribution of ISWI-containing remodeling complexes to the architecture of compensated chromatin, and we suggest a role for this remodeling factor in dosage compensation.

View Article: PubMed Central - PubMed

Affiliation: Department of Cell Biology and Department of Biology, Emory University, Atlanta, GA 30322, USA.

ABSTRACT
The regulatory mechanism of dosage compensation is the paramount example of epigenetic regulation at the chromosomal level. In Drosophila, this mechanism, designed to compensate for the difference in the dosage of X-linked genes between the sexes, depends on the MSL complex that enhances the transcription of the single dose of these genes in males. We have investigated the function of various subunits of the complex in mediating dosage compensation. Our results confirm that the highly enriched specific acetylation of histone H4 at lysine 16 of compensated genes by the histone acetyl transferase subunit MOF induces a more disorganized state of their chromatin. We have determined that the association of the MSL complex reduces the level of negative supercoiling of the deoxyribonucleic acid of compensated genes, and we have defined the role that the other subunits of the complex play in this topological modification. Lastly, we have analyzed the potential contribution of ISWI-containing remodeling complexes to the architecture of compensated chromatin, and we suggest a role for this remodeling factor in dosage compensation.

Show MeSH