title: Analysis of the heterochromatin protein 1 (HP1) interactome in Drosophila.
abstract: Heterochromatin protein 1 (HP1) was first described in Drosophila melanogaster as a heterochromatin associated protein required for epigenetic gene silencing. Most eukaryotes have at least three HP1 homologs that play differential roles in heterochromatin and euchromatin. However, despite the fact that the three HP1 proteins bind to different regions of the genome, several studies show that most of the interactions occur in a manner specific to HP1a. In addition, little is known about the overall interaction network of the three Drosophila HP1 homologs, HP1a, HP1b, and HP1c. Here, we performed the first comprehensive proteomic analysis of Drosophila HP1 homologs by coupling a double-affinity purification approach with MudPIT analysis to identify interacting proteins of Drosophila HP1. We discovered 160-310 proteins co-eluted with HP1, including a number of novel HP1-binding partners along with the previously identified HP1 binding proteins. Finally, we showed that slight and unique binding preferences might exist between the three HP1 proteins in Drosophila. These studies are the first to systematically analyze the interactome of HP1 paralogs and provide the basic clues as to the molecular mechanism by which HP1 might control cellular processes.
  
  
  CONCLUSIONS
  Most eukaryotes have at least three HP1 homologs with similar domain structures but with differential roles in heterochromatin and euchromatin. However, little is known about the overall interactome of the three Drosophila HP1 homologs, HP1a, HP1b, and HP1c. The present study compared interacting proteins of three HP1 homologs in Drosophila. To better understand the underlying mechanisms for gene regulation of HP1, a double-affinity purification and MudPIT mass spectrometry were employed to identify differential proteins as well as common binding proteins of HP1. Therefore, this study provides not only the comparative proteomic analysis but also molecular mechanism underlying the HP1 homolog-specific function.
authors.affiliation: College of Pharmacy, Yonsei Institute of Pharmaceutical Sciences, Yonsei University, Incheon, 406-840, Republic of Korea.
authors.forename: Hyun-Wook
authors.initials: HW
authors.lastname: Ryu
authors.affiliation: College of Pharmacy, Yonsei Institute of Pharmaceutical Sciences, Yonsei University, Incheon, 406-840, Republic of Korea.
authors.forename: Dong Hoon
authors.initials: DH
authors.lastname: Lee
authors.affiliation: Stowers Institute for Medical Research, 1000 East 50th Street, Kansas City, MO 64110, USA.
authors.forename: Laurence
authors.initials: L
authors.lastname: Florens
authors.affiliation: Stowers Institute for Medical Research, 1000 East 50th Street, Kansas City, MO 64110, USA.
authors.forename: Selene K
authors.initials: SK
authors.lastname: Swanson
authors.affiliation: Stowers Institute for Medical Research, 1000 East 50th Street, Kansas City, MO 64110, USA; Department of Pathology and Laboratory Medicine, University of Kansas Medical Center, Kansas City, KS 66160, USA.
authors.forename: Michael P
authors.initials: MP
authors.lastname: Washburn
authors.affiliation: College of Pharmacy, Yonsei Institute of Pharmaceutical Sciences, Yonsei University, Incheon, 406-840, Republic of Korea. Electronic address: soheekwon@yonsei.ac.kr.
authors.forename: So Hee
authors.initials: SH
authors.lastname: Kwon
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D002467:Cell Nucleus / Q000378:metabolism; D002843:Chromatin / Q000378:metabolism; D000090266:Chromobox Protein Homolog 5; D002868:Chromosomal Proteins, Non-Histone / Q000378:metabolism*; D029721:Drosophila Proteins / Q000378:metabolism*; D004331:Drosophila melanogaster / Q000378:metabolism*; D000939:Epitopes / Q000378:metabolism; D005786:Gene Expression Regulation; D020868:Gene Silencing; D013058:Mass Spectrometry; D008856:Microscopy, Fluorescence; D008969:Molecular Sequence Data; D011485:Protein Binding; D025941:Protein Interaction Mapping; D040901:Proteomics
chemical_list: D002843:Chromatin; D002868:Chromosomal Proteins, Non-Histone; D029721:Drosophila Proteins; D000939:Epitopes; D000090266:Chromobox Protein Homolog 5
keywords: HP1a; HP1b; HP1c; Interactome; MudPIT