The double-stranded DNA-binding proteins TEBP-1 and TEBP-2 form a telomeric complex with POT-1

Abstract

Telomeres are bound by dedicated proteins, which protect them from DNA damage and regulate telomere length homeostasis. In the nematode Caenorhabditis elegans, a comprehensive understanding of the proteins interacting with the telomere sequence is lacking. Here, we harnessed a quantitative proteomics approach to identify TEBP-1 and TEBP-2, two paralogs expressed in the germline and embryogenesis that associate to telomeres in vitro and in vivo. tebp-1 and tebp-2 mutants display strikingly distinct phenotypes: tebp-1 mutants have longer telomeres than wild-type animals, while tebp-2 mutants display shorter telomeres and a Mortal Germline. Notably, tebp-1;tebp-2 double mutant animals have synthetic sterility, with germlines showing signs of severe mitotic and meiotic arrest. Furthermore, we show that POT-1 forms a telomeric complex with TEBP-1 and TEBP-2, which bridges TEBP-1/-2 with POT-2/MRT-1. These results provide insights into the composition and organization of a telomeric protein complex in C. elegans.

The Caenorhabditis elegans TDRD5/7-like protein, LOTR-1, interacts with the helicase ZNFX-1 to balance epigenetic signals in the germline

“…Western blot in S3D Fig was performed exactly as described [ 113 ] using a mouse monoclonal anti-FLAG antibody (Sigma-Aldrich, #F3165) in a 1:5000 dilution in Skim Milk solution (1x PBS, 0.1% Tween-20, 5% (w/v) Skim Milk Powder), and a rabbit anti-Actin antibody (Sigma-Aldrich, #A2066) in a 1:500 dilution in Skim Milk Solution. We first probed the IP bait with a HRP-linked secondary antibody (Cell Signaling Technology, anti-mouse IgG, #7076; 1:10,000 dilution in Skim Milk Solution), and Actin was subsequently probed with a LI-COR secondary antibody (LI-COR IRDye 800CW Donkey anti-Rabbit IgG (H+L), #926–32213, in a 1:15,000 dilution in Skim Milk Solution).…”

POT-3 preferentially binds the terminal DNA-repeat on the telomeric G-overhang

“…Indeed, there is ∼100× more POT-2 protein in worm embryos than POT-3 ( 26 ). This disparity in abundance might also explain why POT-2 but not POT-3 was detected via mass spectrometry in pulldowns using the telomere binding proteins TEBP-1 and TEBP-2 ( 27 ). Thus, in a pot-2 mutant, POT-3 is no longer restricted to the terminal telomeric repeat and may now mislocalise to other regions such as the displaced G-strand formed next to a T-loop.…”

“…The precise function of the C-overhang is unclear. However, it is likely to be important as POT-1 is required to maintain the physical interaction between the telomeric dsDNA binders (TEBP-1/2) and the telomeric ssDNA binder (POT-2) in vivo ( 27 ). POT-1 also promotes telomeric association with the nuclear envelope during embryogenesis ( 14 ).…”

Unzipped assemblies of polyploid root-knot nematode genomes reveal new kinds of unilateral composite telomeric repeats

“…Two proteins in C. elegans, TEBP1/DTN-1 and TEBP2/DTN-2, were shown to bind double-stranded telomeric DNA and POT1 (Yamamoto et al, 2021). Sterility is observed after one or several generations in tebp-1; tebp-2 double mutants (Dietz et al, 2021;Yamamoto et al, 2021). A single TEBP homolog was found in many nematodes including in C. briggsae (Dietz et al, 2021).…”

“…Sterility is observed after one or several generations in tebp-1; tebp-2 double mutants (Dietz et al, 2021;Yamamoto et al, 2021). A single TEBP homolog was found in many nematodes including in C. briggsae (Dietz et al, 2021).…”