title: Sequence-specific binding to telomeric DNA by CEH-37, a homeodomain protein in the nematode Caenorhabditis elegans.
abstract: Caenorhabditis elegans can serve as a model system to study telomere functions due to its similarity to higher organisms in telomere structures. We report here the identification of the nematode homeodomain protein CEH-37 as a telomere-binding protein using a yeast one-hybrid screen. The predicted three-dimensional model of the homeodomain of CEH-37, which has a typical helix-loop-helix structure, was similar to that of the Myb domain of known telomere-binding proteins, which is also a helix-loop-helix protein, despite little amino acid sequence similarity. We demonstrated the specific binding of CEH-37 to the nematode telomere sequences in vitro by competition assays. We determined that CEH-37 binding required at least 1.5 repeats of TTAGGC and that the core sequence for binding was GGCTTA. We found that CEH-37 had an ability to bend telomere sequence-containing DNA, which is the case for other known telomere-binding proteins such as TRF1 and RAP1, indicating that CEH-37 may be involved in establishing or maintaining a secondary structure of the telomeres in vivo. We also demonstrated that CEH-37 was primarily co-localized to the chromosome ends in vivo, indicating that CEH-37 may play roles in telomere functions. Consistent with this, a ceh-37 mutation resulting in a truncated protein caused a weak high incidence of male phenotype, which may have been caused by chromosome instability. The identification of CEH-37 as a telomere-binding protein may represent an evolutionary conservation of telomere-binding proteins in terms of tertiary protein structure rather than primary amino acid sequence.
authors.affiliation: National Research Laboratory and the Molecular Aging Research Center, Department of Biology, Yonsei University, 134 Shinchon, Seodaemun-ku, Seoul 120-749, Korea.
authors.forename: Seung Hyun
authors.initials: SH
authors.lastname: Kim
authors.forename: Soon Baek
authors.initials: SB
authors.lastname: Hwang
authors.forename: In Kwon
authors.initials: IK
authors.lastname: Chung
authors.forename: Junho
authors.initials: J
authors.lastname: Lee
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D017173:Caenorhabditis elegans; D029742:Caenorhabditis elegans Proteins / Q000737:chemistry* / Q000378:metabolism*; D004247:DNA / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000378:metabolism; D018398:Homeodomain Proteins / Q000737:chemistry* / Q000378:metabolism*; D008856:Microscopy, Fluorescence; D008969:Molecular Sequence Data; D010641:Phenotype; D011485:Protein Binding; D017433:Protein Structure, Secondary; D017434:Protein Structure, Tertiary; D034622:RNA Interference; D017386:Sequence Homology, Amino Acid; D016615:Telomere / Q000378:metabolism / Q000648:ultrastructure*; D020798:Two-Hybrid System Techniques
chemical_list: C476585:CEH-37 protein, C elegans; D029742:Caenorhabditis elegans Proteins; D004268:DNA-Binding Proteins; D018398:Homeodomain Proteins; D004247:DNA