The alternative packaging of DNA into euchromatic and heterochromatic forms can be stably maintained in differentiated cells, and represents an important form of epigenetic inheritance. Malfunction in the heterochromatin system can lead to misregulation of gene expression, as well as chromosome instability, and is a contributing factor in many health problems, including cancer and genetically-based developmental disabilities. Heterochromatin packaging can be perpetuated and spread by virtue of an interacting set of structural proteins, with Heterochromatin Protein 1 (HP1a) playing a key role in both recognizing a critical histone modification mark (methylation of H3K9) and interacting with the histone methyl transferase (HMT). Our long term goal is to understand why and how certain regions of the genome are selected for heterochromatin assembly, and to identify the required chromosomal proteins and their interactions. All work will be carried out in Drosophila, a model system that allows genetic, cytological, and biochemical approaches;position effect variegation (PEV) is used as an indicator of heterochromatin packaging. Our studies of chromosome four (entirely heterochromatic by several measures) indicate that remnants of the 1360 DNA transposon serve as targets for heterochromatin formation, but that stable heterochromatin requires a high repeat density. In the first specific aim, the role of genome organization and identity of specific targets will be tested using reporter P elements with different types and copy number of repetitious elements. In our second aim, binding studies and structural analysis will explore how HP1a discriminates among its several partners to assemble a silencing structure. The HMT specific for chromosome four will be identified, its pattern of interactions explored, and the impact on spreading considered. Additional heterochromatin components will be identified by screening for proteins interacting with HP2 in a yeast two hybrid system exploiting recently recovered HP2 mutations as controls. In a third long-term aim, we will ask whether some fourth chromosome genes function optimally in a heterochromatic environment, and explore that adaptation. Taken together these studies will illuminate how heterochromatin formation is initiated and sustained, and will provide new insights into gene regulation at the domain level.

Agency
National Institute of Health (NIH)
Institute
National Institute of General Medical Sciences (NIGMS)
Type
Research Project (R01)
Project #
5R01GM068388-23
Application #
7848058
Study Section
Molecular Genetics B Study Section (MGB)
Program Officer
Carter, Anthony D
Project Start
1987-12-01
Project End
2013-08-31
Budget Start
2010-07-01
Budget End
2013-08-31
Support Year
23
Fiscal Year
2010
Total Cost
$458,451
Indirect Cost
Name
Washington University
Department
Biology
Type
Schools of Arts and Sciences
DUNS #
068552207
City
Saint Louis
State
MO
Country
United States
Zip Code
63130
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Leung, Wilson (see original citation for additional authors) (2015) Drosophila muller f elements maintain a distinct set of genomic properties over 40 million years of evolution. G3 (Bethesda) 5:719-40
Eissenberg, Joel C; Elgin, Sarah C R (2014) HP1a: a structural chromosomal protein regulating transcription. Trends Genet 30:103-10
Wang, Sidney H; Nan, Ruth; Accardo, Maria C et al. (2014) A distinct type of heterochromatin at the telomeric region of the Drosophila melanogaster Y chromosome. PLoS One 9:e86451
Sentmanat, M; Wang, S H; Elgin, S C R (2013) Targeting heterochromatin formation to transposable elements in Drosophila: potential roles of the piRNA system. Biochemistry (Mosc) 78:562-71
Gu, Tingting; Elgin, Sarah C R (2013) Maternal depletion of Piwi, a component of the RNAi system, impacts heterochromatin formation in Drosophila. PLoS Genet 9:e1003780
Mendez, Deanna L; Mandt, Rebecca E; Elgin, Sarah C R (2013) Heterochromatin Protein 1a (HP1a) partner specificity is determined by critical amino acids in the chromo shadow domain and C-terminal extension. J Biol Chem 288:22315-23
Sentmanat, Monica F; Elgin, Sarah C R (2012) Ectopic assembly of heterochromatin in Drosophila melanogaster triggered by transposable elements. Proc Natl Acad Sci U S A 109:14104-9
Riddle, Nicole C; Jung, Youngsook L; Gu, Tingting et al. (2012) Enrichment of HP1a on Drosophila chromosome 4 genes creates an alternate chromatin structure critical for regulation in this heterochromatic domain. PLoS Genet 8:e1002954
Mendez, Deanna L; Kim, Daesung; Chruszcz, Maksymilian et al. (2011) The HP1a disordered C terminus and chromo shadow domain cooperate to select target peptide partners. Chembiochem 12:1084-96

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