Sequence-specific binding to telomeric DNA by CEH-37, a homeodomain protein in the nematode Caenorhabditis elegans.
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.
Kim
Seung Hyun
SH
National Research Laboratory and the Molecular Aging Research Center, Department of Biology, Yonsei University, 134 Shinchon, Seodaemun-ku, Seoul 120-749, Korea.
Hwang
Soon Baek
SB
Chung
In Kwon
IK
Lee
Junho
J
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
C476585:CEH-37 protein, C elegans; D029742:Caenorhabditis elegans Proteins; D004268:DNA-Binding Proteins; D018398:Homeodomain Proteins; D004247:DNA