Rad6–Bre1-mediated H2B ubiquitination regulates telomere replication by promoting telomere-end resection

Abstract

Rad6 and Bre1, ubiquitin-conjugating E2 and E3 enzymes respectively, are responsible for histone H2B lysine 123 mono-ubiquitination (H2Bub1) in Saccharomyces cerevisiae. Previous studies have shown that Rad6 and Bre1 regulate telomere length and recombination. However, the underlying molecular mechanism remains largely unknown. Here we report that H2BK123 mutation results in telomere shortening, while inactivation of Ubp8 and/or Ubp10, deubiquitinases of H2Bub1, leads to telomere lengthening in Rad6–Bre1-dependent manner. In telomerase-deficient cells, inactivation of Rad6–Bre1 pathway retards telomere shortening rate and the onset of senescence, while deletion of UBP8 and/or UBP10 accelerates senescence. Thus, Rad6–Bre1 pathway regulates both telomere length and recombination through its role in H2Bub1. Additionally, inactivation of both Rad6–Bre1–H2Bub1 and Mre11–Rad50–Xrs2 (MRX) pathways causes synthetic growth defects and telomere shortening in telomerase-proficient cells, and significantly accelerates senescence and eliminates type II telomere recombination in telomerase-deficient cells. Furthermore, RAD6 or BRE1 deletion, or H2BK123R mutation decreases the accumulation of ssDNA at telomere ends. These results support the model that Rad6–Bre1–H2Bub1 cooperates with MRX to promote telomere-end resection and thus positively regulates both telomerase- and recombination-dependent telomere replication. This study provides a mechanistic link between histone H2B ubiquitination and telomere replication.

The evolutionarily conserved factor Sus1/ENY2 plays a role in telomere length maintenance

“…3c (see lanes 8, 9 and 10), telomeres were also slightly longer compared to the wild-type for all DUBm mutant. This is consistent with a recent study demonstrating that inactivation of both Ubp8 and Ubp10 promotes telomere elongation (Wu et al 2017b). Since the phenotype of elongated telomeres are shared by all DUBm, our results suggest that Ubp8 activity takes place in the context of the DUBm as a complete module, by playing a relevant role in telomere homeostasis in yeast.…”

“…However, a precise correlation between telomere length and global H2B monoubiquitination levels is unknown. The data presented in this study, together with recent work in humans and yeast (Armour et al 2013;Atanassov et al 2016;Wu et al 2017b) suggested that a normal cycle of ubiquitination and deubiquitination of H2BK123, as has been found for other proteins (Chu et al 2016;Jiang 2016;Nostramo and Herman 2016), influences telomere length. Thus, we decided to investigate whether mutants with short telomeres, such as rsc2Δ, resulted in a depletion of H2BK123ub 1 .…”

The MRE11–RAD50–NBS1 Complex Conducts the Orchestration of Damage Signaling and Outcomes to Stress in DNA Replication and Repair

“…Also, telomere elongation may depend on X-ray repair cross-complementing protein 3 (XRCC3) and NBS1 in stem cells (169). The MRX complex may also assist Rad6 and Bre1 ubiquitin-conjugating enzymes in successful telomere replication (170). …”

Simultaneous visualisation of the complete sets of telomeres from the MmeI generated terminal restriction fragments in yeasts

“…One copy of RIF1 was deleted in BY4743 by a pRS306-rif1Δ cassette as descried previously (Liu et al, 2016;Wu et al, 2017). Rif1-5UTR-F & T7 and Rif1-orf-F& Rif1-orf-R were used to confirm RIF1 deletion.…”