We use dosage compensation in Drosophila as a model to understand how chromatin domains are created and maintained for precise control of gene expression. Dosage compensation increases transcriptional output from the single male X chromosome to balance X and autosomal gene expression in males (XY) as it is in females (XX). This is achieved by the MSL complex, which binds to active genes on the X chromosome, and acetylates histone H4 on Lys 16 within gene bodies. Initial targeting of the X occurs at sites of non-coding roX1 and roX2 RNA synthesis, and at ~250 """"""""chromatin entry sites"""""""" through binding to 21 bp MSL recognition elements (MREs) that are enriched, but not exclusive to the X chromosome. A second, sequence-independent """"""""spreading"""""""" step leads to binding of virtually all active genes on X in cis. Once bound to gene bodies, the MSL complex somehow increases transcriptional output approximately two-fold. In this proposal, we have developed three specific aims to address the most intriguing aspects of dosage compensation at a mechanistic level.
In Aim 1, we ask how a simple sequence can function specifically on X to nucleate MSL spreading.
In Aim 2, we ask when and how spreading to active genes occurs.
In Aim 3, we ask how the MSL complex increases transcription of X linked genes. Our current approaches reflect the rapid changes in genomic analysis that have occurred in the field. We continue to utilize a model genetic approach, but we can now, for the first time, follow the manipulation of genotype with analysis of the resulting chromosomal and transcriptional phenotypes at very precise, sometimes base pair resolution. Success in these approaches should serve as a model for understanding how the genome is organized for the precise and coordinate regulation of gene expression.

Public Health Relevance

The packaging of the genome into active and silent domains plays a key role in its fidelity in higher organisms, so it is not surprising that aberrations in chromatin-modifying complexes are now recognized to play a crucial role in human diseases, including cancer. Our studies are aimed at understanding how chromatin domains are created and maintained for the precise control of gene expression, using a powerful model system to explore novel insights into epigenetic regulation.

Agency
National Institute of Health (NIH)
Institute
National Institute of General Medical Sciences (NIGMS)
Type
Research Project (R01)
Project #
2R01GM045744-24
Application #
8704051
Study Section
Molecular Genetics B Study Section (MGB)
Program Officer
Carter, Anthony D
Project Start
1991-04-01
Project End
2018-03-31
Budget Start
2014-05-01
Budget End
2015-03-31
Support Year
24
Fiscal Year
2014
Total Cost
Indirect Cost
Name
Brigham and Women's Hospital
Department
Type
DUNS #
City
Boston
State
MA
Country
United States
Zip Code
02115
Kuroda, Mitzi I; Hilfiker, Andres; Lucchesi, John C (2016) Dosage Compensation in Drosophila-a Model for the Coordinate Regulation of Transcription. Genetics 204:435-450
Zee, Barry M; Alekseyenko, Artyom A; McElroy, Kyle A et al. (2016) Streamlined discovery of cross-linked chromatin complexes and associated histone modifications by mass spectrometry. Proc Natl Acad Sci U S A 113:1784-9
Alekseyenko, Artyom A; McElroy, Kyle A; Kang, Hyuckjoon et al. (2015) BioTAP-XL: Cross-linking/Tandem Affinity Purification to Study DNA Targets, RNA, and Protein Components of Chromatin-Associated Complexes. Curr Protoc Mol Biol 109:21.30.1-32
Lucchesi, John C; Kuroda, Mitzi I (2015) Dosage compensation in Drosophila. Cold Spring Harb Perspect Biol 7:
Ferrari, Francesco; Alekseyenko, Artyom A; Park, Peter J et al. (2014) Transcriptional control of a whole chromosome: emerging models for dosage compensation. Nat Struct Mol Biol 21:118-25
McElroy, Kyle A; Kang, Hyuckjoon; Kuroda, Mitzi I (2014) Are we there yet? Initial targeting of the Male-Specific Lethal and Polycomb group chromatin complexes in Drosophila. Open Biol 4:140006
Alekseyenko, Artyom A; Gorchakov, Andrey A; Zee, Barry M et al. (2014) Heterochromatin-associated interactions of Drosophila HP1a with dADD1, HIPP1, and repetitive RNAs. Genes Dev 28:1445-60
Ferrari, Francesco; Plachetka, Annette; Alekseyenko, Artyom A et al. (2013) ""Jump start and gain"" model for dosage compensation in Drosophila based on direct sequencing of nascent transcripts. Cell Rep 5:629-36
Ferrari, F; Jung, Y L; Kharchenko, P V et al. (2013) Comment on ""Drosophila dosage compensation involves enhanced Pol II recruitment to male X-linked promoters"". Science 340:273
Zhou, Qi; Ellison, Christopher E; Kaiser, Vera B et al. (2013) The epigenome of evolving Drosophila neo-sex chromosomes: dosage compensation and heterochromatin formation. PLoS Biol 11:e1001711

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