17 / 22
Page 56
allied
academies
Archives of Industrial Biotechnology | Volume 2
May 14-15, 2018 | Montreal, Canada
World Yeast Congress
F
ailure to maintain telomeres leads to their progressive
erosion at each cell division and replicative senescence,
a cell cycle arrest mediated by the DNA damage checkpoint
signaling. To understand the flow of signaling events from
telomeres to cell proliferation cessation, we set up a
microfluidics-based live-cell imaging assay to investigate
replicative senescence in individual
Saccharomyces
cerevisiae
cell lineages following telomerase inactivation.
Using this strategy, we found that most lineages experience
an abrupt and irreversible transition consistent with a
model where the first telomere reaching a critical short
length triggers senescence onset. However, many lineages
undergo frequent reversible DNA damage checkpoint cell-
cycle arrests, beginning soon after telomerase inactivation
(Xu et al, Nat Com, 2015). Here, we provide evidence that
this novel phenotype stems from replicative stress at
telomeres and gives rise to genomic instability, a hallmark
of senescence escapers. First, we demonstrate that the DNA
damage tolerance pathway is critical for viability immediately
after telomerase inactivation. More specifically, Rad5 and
Rad51 operate cooperatively and sequentially to bypass
replication barriers at telomeres and the repair choice is
modulated by Srs2 and orchestrated by PCNA modifications.
Second, the long reversible arrests are suppressed in an
adaptation defective mutant of the polo-like kinase Cdc5.
This mutant strongly reduces the senescence-specific
genome instability and alters the post-senescence survival
patterns. Thus, replication stress at telomeres revealed by
telomerase inactivation, initiates repair and adaptation
pathways, leading to genomic instability and to potential
post-senescence survival. Overall, our findings provide
an essential mechanistic link between ageing and cancer
emergence.
e:
teresa.teixeira@ibpc.frReal-time analysis of replicative senescence at single cell resolution
Maria Teresa Teixeira
1
, Zhou Xu
1
, Héloïse Coutelier
1
, Erin Henninger
1
, Pascale Jolivet
1
, Stefano Mattarocci
1
, Serge Pelet
2
, Marie Doumic
3
and
Gilles Charvin
4
1
Sorbonne Université, France
2
University of Lausanne, Switzerland
3
Université Pierre et Marie Curie, France
4
Institut de Génétique et de Biologie Moléculaire et Cellulaire, France