Identification of HMG-5 as a double-stranded telomeric DNA-binding protein in the nematode Caenorhabditis elegans.
Many protein components of telomeres, the multifunctional DNA-protein complexes at the ends of eukaryotic chromosomes, have been identified in diverse species ranging from yeast to humans. In Caenorhabditis elegans, CEH-37 has been identified by a yeast one hybrid screen to be a double-stranded telomere-binding protein. However, the role of CEH-37 in telomere function is unclear because a deletion mutation in this gene does not cause severe telomere defects. This observation raises the possibility of the presence of genetic redundancy. To identify additional double-stranded telomere-binding proteins in C. elegans, we used a different approach, namely, a proteomic approach. Affinity chromatography followed by Finnigan LCQ ion trap mass spectrometer analysis allowed us to identify several candidate proteins. We further characterized one of these, HMG-5, which is encoded by F45E4.9. HMG-5 bound to double-stranded telomere in vitro as shown by competition assays. At least two telomeric DNA repeats were needed for this binding. HMG-5 was expressed in the nuclei of the oocytes and all embryonic cells, but not in the hatched larvae or adults. HMG-5 mainly localized to the chromosomal ends, indicating that HMG-5 also binds to telomeres in vivo. These observations suggest that HMG-5 may participate, together with CEH-37, in early embryogenesis by acting at the telomeres.
Im
Seol Hee
SH
National Research Laboratory, Department of Biology, Yonsei University, 134 Shinchon, Seodaemun-ku, Seoul 120-749, South Korea.
Lee
Junho
J
D000595:Amino Acid Sequence; D000818:Animals; D017173:Caenorhabditis elegans / Q000737:chemistry* / Q000196:embryology / Q000378:metabolism; D029742:Caenorhabditis elegans Proteins / Q000235:genetics / Q000302:isolation & purification* / Q000378:metabolism*; D002846:Chromatography, Affinity; D002875:Chromosomes / Q000378:metabolism; D004247:DNA / Q000737:chemistry / Q000378:metabolism; D008958:Models, Molecular; D008969:Molecular Sequence Data; D011485:Protein Binding; D017433:Protein Structure, Secondary; D011994:Recombinant Proteins / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism; D017386:Sequence Homology, Amino Acid; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization / Q000379:methods; D013379:Substrate Specificity; D016615:Telomere / Q000235:genetics / Q000378:metabolism* / Q000648:ultrastructure; D034501:Telomere-Binding Proteins / Q000235:genetics / Q000302:isolation & purification* / Q000378:metabolism*
D029742:Caenorhabditis elegans Proteins; D011994:Recombinant Proteins; D034501:Telomere-Binding Proteins; D004247:DNA