Washington University in St. Louis
Campus Box 1137
One Brookings Drive
St. Louis, MO 63130-4899
We are interested in the role that chromatin structure plays in gene regulation, both effects from packaging large domains and local effects of the nucleosome array. Working with Drosophila melanogaster, we have used a transposable P element containing a copy of the white gene, a visible marker for gene silencing, and a copy of hsp26, a well-characterized inducible gene, to examine the effect of insertion into different chromosomal domains. While these genes are fully active in euchromatic domains, silencing (similar to Position Effect Variegation) is observed on insertion into pericentric heterochromatin, telomeres, and sites within the small fourth chromosome. Both changes in the local nucleosome array, and the spatial organization of the nucleus, appear critical in determining gene silencing. The fourth chromosome, which appears entirely heterochromatic by many criteria, but has ~80 genes, is the focus of our studies. Mapping experiments indicate that heterochromatin formation can be targeted by the presence of a repetitious element, 1360, and perhaps by other similar elements. Genetic analysis has shown that heterochromatic silencing is dependent on the RNAi machinery. Work is ongoing to determine the mechanism of heterochromatin targeting, and to analyze the role of critical heterochromatin-associated proteins, including HP1 and HP2.
Photo caption: Our P-element construct contains a visible marker for variegation, hsp70-white, and a marked copy of hsp26 for accompanying studies of chromatin structure. Many fly lines have been recovered showing a PEV phenotype (A); all have P element inserts in the pericentric heterochromatin (as shown for this case by in situ hybridization of the polytene chromosomes with the entire P element; see B), telomeres and the small fourth chromosome.
Leung, W….[940 students, 72 faculty]…Elgin, SCR (2015) The Drosophila Muller F elements maintain a distinct set of genomics properties over 40 million years of evolution. G3: GENES, GENOMES, GENETICS 5: 719-740.
Ho, JW, Jung YL, Liu T, Alver BH, Lee S, Ikegami K, Sohn KA, Minoda A, Tolstorukov MY, Appert A, Parker SC, Gu T, Kundaje A, Riddle NC, Bishop E, Egelhofer TA, Hu SS, Alekseyenko AA, Rechtsteiner A, ….[42 additional co-authors]…Kingston RE, Kim JH, Bernstein BE, Dernburg AF,Pirrotta V, Kuroda MI, Noble WS, Tullius TD, Kellis M, MacAlpine DM, Strome S, Elgin SC, Liu XS, Lieb JD, Ahringer J, Karpen GH, Park PJ (2014) Comparative analysis of metazoan chromatin organization. Nature 512z; 449-52. PMID: 25164756
Eissenberg, JC & SCR Elgin (2014) HP1a: A structural chromosomal protein regulatingtranscription. Tr Genetics 30: 103-10. PMCID: PMC3991861
Gu, T, and Elgin, SCR (2013) Maternal delpletion of Piwi, a component of the RNAi system, impacts heterochromatin formation in Drosophila. PLoS Genetics 9: e1003780/ PMCID: PMC3777992
Riddle, NC, YL Jung, T Gu, AA Alekseyenko, D Asker, H Gui, PV Kharchenko, A Minoda, A Plachetka, YB Schwartz, MY Tolstorukov, MI Kuroda, V Pirrotta, GH Karpen, PJ Park, SCR Elgin. (2012) “Enrichment of HP1a on Drosophila chromosome 4 genes creates an alternative chromatin structure critical for regulation in this heterochromatic domain,” PLoS Genetics 8: e1002954 PMCID: PMC3447959
Wang, S H, and Elgin, SCR (2011) “Drosophila Piwi functions downstream of piRNA production mediating a chromatin-based silencing mechanism in female germline,” Proc Natl Acad Sci USA. 108: 21164-69. PMCID: PMC3248523.