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SRX23849696: GSM8128701: embryo, 50h, rep4; Ascaris suum; OTHER
1 ILLUMINA (Illumina NovaSeq 6000) run: 64.8M spots, 19.6G bases, 6.1Gb downloads

External Id: GSM8128701_r1
Submitted by: 420C, Biochemistry & Cellular and Molecular Biology, University of Tennessee Knoxville
Study: End resection and telomere healing of DNA double-strand breaks during nematode programmed DNA elimination
show Abstracthide Abstract
Most DNA double-strand breaks (DSBs) are harmful to genome integrity. However, some forms of DSBs are essential to biological processes, such as meiotic recombination and V(D)J recombination. DSBs are also required for programmed DNA elimination (PDE) in ciliates and nematodes. In nematodes, the DSBs are healed with telomere addition. While telomere addition sites have been well-characterized, little is known regarding the DSBs that fragment nematode chromosomes. Here, we used embryos from the nematode Ascaris to study the timing of PDE breaks and examine the DSBs and their end processing. Using END-seq, we characterize the DSB ends and demonstrate that DNA breaks are introduced before mitosis, followed by extensive end resection. The resection profile is unique for each break site, and the resection generates 3' overhangs before the addition of telomeres. Interestingly, telomere healing occurs much more frequently on retained DSB ends than on eliminated ends. This biased repair of the DSB in Ascaris is likely due to the sequestration of the eliminated DNA into micronuclei, preventing their ends from telomere healing. Additional DNA breaks occur within the eliminated DNA in both Ascaris and Parascaris, ensuring chromosomal breakage and providing a fail-safe mechanism for nematode PDE. Overall design: END-seq on Ascaris suum and Parascaris univalens early embryos undergoing programmed DNA elimination. Includes biological replicates for various stages of embryo development.
Sample: embryo, 50h, rep4
SAMN40279009 • SRS20669772 • All experiments • All runs
Organism: Ascaris suum
Library:
Name: GSM8128701
Instrument: Illumina NovaSeq 6000
Strategy: OTHER
Source: GENOMIC
Selection: other
Layout: PAIRED
Construction protocol: Ascaris females were collected, and the fertilized embryos (0hr, 1-cell before prenuclear fusion) were harvested and processed as previously described (Wang et al. 2011, Wang et al. 2014). Ascaris 0hr samples were incubated at 30°C with constant shaking for the desired time (from 50hr to 98hr). For all molecular experiments, the eggshells were first de-coated with bleach treatment (0.4 M KOH, 2% sodium hypochlorite) for 1.5 hours at 30°C. Parascaris samples were collected as described (Simmons et al. 2023, Wang et al. 2017). Parascaris eggs were prepared similarly to Ascaris, except the incubation was carried out at 37°C and the embryonation time was shorter (10-14hr). An adapted END-seq protocol was used (Canela et al. 2016, Wong et al. 2021). Embryos were embedded in agarose plugs. Some plugs were treated with the restriction enzymes as internal controls. Plugs were treated with exonuclease VII and exonuclease T. Blunt ends were A-tailed and capped with END-seq adaptor 1 (Canela et al. 2016). Plugs were melted and DNA was sheared to 200-300 bp with a Covaris M220 focused ultrasonicator. DNA fragments containing END-seq adaptor 1 were isolated with Dynabeads MyOne Streptavidin C1. END-seq adaptor 2 was ligated to the sheared ends of the A-tailed DNA fragments. The hairpins within the adaptors were digested with USER, and the DNA was amplified with Illumina TruSeq primers and barcodes. The following modifications were made to the END-seq protocol to capture break ends with different features. For the direct capture method, we excluded the exonuclease VII and exonuclease T treatments. For the all-END protocol, the plugs were treated with T4 polymerase (with dNTPs).
Runs: 1 run, 64.8M spots, 19.6G bases, 6.1Gb
Run# of Spots# of BasesSizePublished
SRR2823859564,750,79719.6G6.1Gb2024-03-15

ID:
32153679

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