Molecular dynamics of de novo telomere heterochromatin formation in budding yeast

• Published in: Journal of genetics and genomics Vol. 43; no. 7; pp. 451 - 465
• Main Authors: Duan, Yi-Min, Zhou, Bo-O., Peng, Jing, Tong, Xia-Jing, Zhang, Qiong-Di, Zhou, Jin-Qiu
• Format: Journal Article
• Language: English
• Published: China Elsevier Ltd 20.07.2016
• Subjects: Aldose-Ketose Isomerases - deficiency; Aldose-Ketose Isomerases - genetics; Base Sequence; Gene Silencing; Genetic Loci - genetics; Heterochromatin; Heterochromatin - genetics; Nucleosome positioning; Repressor Proteins - deficiency; Repressor Proteins - genetics; Saccharomyces cerevisiae - genetics; Saccharomyces cerevisiae - metabolism; Saccharomyces cerevisiae Proteins - genetics; Sir; Telomerase - metabolism; Telomere; Telomere - genetics; Telomere-Binding Proteins - deficiency; Telomere-Binding Proteins - genetics; yKu; Heterochromatin; yKu; Telomere; Sir; Nucleosome positioning
• ISSN: 1673-8527
• DOI: 10.1016/j.jgg.2016.03.009

In the budding yeast Saccharomyces cerevisiae, heterochromatin structure is found at three chromosome regions, which are homothallic mating-type loci, rDNA regions and telomeres. To address how telomere heterochromatin is assembled under physiological conditions, we employed a de novo telomere addition system, and analyzed the dynamic chromatin changes of the TRPI reporter gene during telomere elongation. We found that integrating a 255-bp, but not an 81-bp telomeric sequence near the TRP1 promoter could trigger Sir2 recruitment, active chromatin mark（s）＇ removal, chromatin compaction and TRP1 gene silencing, indicating that the length of the telomeric sequence inserted in the internal region of a chromosome is critical for determining the chromatin state at the proximal region. Interestingly, Rill but not Rif2 or yKu is indispensable for the formation of intra-chromosomal silent chromatin initiated by telomeric sequence. When an internal short telomeric sequence （e.g., 81 bp） gets exposed to become a de novo telomere, the herterochromatin features, such as Sir recruitment, active chromatin mark（s）＇ removal and chromatin compaction, are detected within a few hours before the de novo telomere reaches a stable length. Our results recapitulate the molecular dynamics and reveal a coherent picture of telomere het- erochromatin formation.