C. elegans telomeres contain G-strand and C-strand overhangs that are bound by distinct proteins.
Single-strand extensions of the G strand of telomeres are known to be critical for chromosome-end protection and length regulation. Here, we report that in C. elegans, chromosome termini possess 3' G-strand overhangs as well as 5' C-strand overhangs. C tails are as abundant as G tails and are generated by a well-regulated process. These two classes of overhangs are bound by two single-stranded DNA binding proteins, CeOB1 and CeOB2, which exhibit specificity for G-rich or C-rich telomeric DNA. Strains of worms deleted for CeOB1 have elongated telomeres as well as extended G tails, whereas CeOB2 deficiency leads to telomere-length heterogeneity. Both CeOB1 and CeOB2 contain OB (oligo-saccharide/oligo-nucleotide binding) folds, which exhibit structural similarity to the second and first OB folds of the mammalian telomere binding protein hPOT1, respectively. Our results suggest that C. elegans telomere homeostasis relies on a novel mechanism that involves 5' and 3' single-stranded termini.
Raices
Marcela
M
The Salk Institute for Biological Studies, 10010 North Torrey Pines Road., La Jolla, CA 92037, USA.
Verdun
Ramiro E
RE
Compton
Sarah A
SA
Haggblom
Candy I
CI
Griffith
Jack D
JD
Dillin
Andrew
A
Karlseder
Jan
J
D000818:Animals; D030801:Animals, Genetically Modified; D017173:Caenorhabditis elegans / Q000235:genetics* / Q000378:metabolism; D002460:Cell Line; D018509:DNA, Helminth / Q000378:metabolism; D004277:DNA, Single-Stranded / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D004625:Embryo, Nonmammalian / Q000378:metabolism; D006801:Humans; D040681:Structural Homology, Protein; D016615:Telomere / Q000737:chemistry / Q000378:metabolism* / Q000648:ultrastructure
D018509:DNA, Helminth; D004277:DNA, Single-Stranded; D004268:DNA-Binding Proteins