Sung, Sanghyun et al. (2013) International Worm Meeting "in vivo isolation of telomeric proteins in the nematode Caenorhabditis elegans."

Seo, Beomseok, Sung, Sanghyun, Lee, Junho

[International Worm Meeting, 2013]

Telomeres are special nucleoprotein complexes that cap the ends of the eukaryotic linear chromosomes to maintain genomic integrity. Many interesting aspects of the telomeres of Caenorhabditis elegans have been studied; for example, the extension of organismic lifespan by longer telomeres and alternative lengthening of telomeres at the organismic level have been reported. It is conceivable that the protein components of the telomeres may have critical roles in these processes as regulators of length, stability, and yet unknown interesting mechanisms of telomeres. Because most telomeric proteins found in higher mammals (or even yeasts) do not have homologous partners in C. elegans, there is a strong need for biochemical approaches to identify them in C. elegans. Previously, we used a nucleic acid affinity capture method to isolate specific proteins associated with telomeric DNA. Although this in vitro method was useful, it had limitations for describing all proteins that may act in the in vivo context. Therefore, in this study, we utilized the recently developed technique called proteomics of isolated chromatin segments(PICh). PICh uses unique nucleic acid to capture the endogenous segments of chromatin which are fixed before hybridization, so it can be a direct and quantitative tool. Currently, we are investigating the telomere-specific proteins of wild type C. elegans.

Seo, Beomseok et al. (2015) International Worm Meeting "Telomere maintenance through recruitment of internal genomic regions."

Seo, Beomseok, Hills, Mark, Oh, Hyun-Seok, Lee, Junho, Sung, Sanghyun, Kim, Chuna, Shim, Jaegal, Choi, Rachael Mi Jung, Kim, Eunkyeong, Lim, Daisy S., Chun, Jongsik, Kim, Hyesook

[International Worm Meeting, 2015]

Telomere is a ribonucleoprotein complex that protects the natural ends of the linear chromosome. Telomere length is mainly maintained by telomerase, a reverse transcriptase that adds telomere repeat sequence. However recombination-dependent mechanism for telomere maintenance also exist in yeast and human cancer cells. In Caenorhabditis elegans, some of telomerase deletion mutant, trt-1(ok410), can maintain the telomere by alternative lengthening of telomeres (ALT). However the molecular mechanism of ALT in worms is largely unknown. In this study, we established stably maintained ALT survivors of worms that activate an ALT mechanism to escape from the sterility phenotype caused by telomerase deletion. By whole genome sequencing and mapping we concluded that mutation may not be required to maintain ALT telomere in these survivors. Interestingly, ALT survivors added either of two specific internal genomic regions as templates for ALT(T-ALT) according to their genetic backgrounds. A T-ALT sequence consists of telomere-like repeat sequence with unrelated sequence in between. T-ALTs had already been copied to a proximal telomere region of the same chromosome prior to ALT activation in nature, and were amplified interchromosomally by ALT activation. Here we propose a hypothesis that the existence of T-ALT structure in the proximal telomere may be one of the prerequisites for ALT activation..