Replication stress and cancer are induced by replication challenging sequences. On these regions the replisome cannot proceed efficiently, the forks stall inducing ss DNA and ds breaks. Telomeres are paradigmatic replication challenging sequences due to the repetitive nature of their sequence, the presence of a capping complex, and the tridimensional organization including G quadruplex pairing. The nuclear envelope contributes to telomere integrity and mutations of lamins, which alter the nuclear envelope, cause telomere dysfunction. We identified a mammalian telomeric protein, AKTIP, involved in telomere replication. Beyond working at telomeres, AKTIP displays a second relevant property: it is a lamin binding partner.
Although many evidence link genome and telomere integrity to the nuclear envelope, the mechanics of this interaction is not yet defined. AKTIP is the first characterized human protein locating at the nuclear envelope involved in telomere replication. This induces to hypothesize that the study of complexes involving AKTIP will give insights into replicative mechanisms at telomeres, into their control by the nuclear envelope, and information on replication stress and tumorigenesis. In particular the proposed experiment are aimed to define the mechanics of AKTIP in replication, to identify factors controlling replication at the nuclear envelope and to get insights into the role of the mouse orthologue of AKTIP, Ft1, in replication and tumorigenesis. Our data, besides clarifying AKTIP role in telomere replication and unraveling the function of factors acting in the same process, will give insights into the implication of nuclear envelope and telomere defects in genome instability and tumorigenesis, as independent and combined insults. This study will provide relevant results contributing to elucidating the molecular drivers linking replication stress and cancer and identifying in this way, putative therapeutic targets.
We expect with this study to obtain relevant results for basic knowledge of replication stress management at telomeres, and of cancer driving molecular mechanisms. Our results will contribute to elucidating the implication of telomeric factors in lymphomagenesis, the mechanism of action of these factors at telomeres and, possibly at other replication challenging sites in the genome. We also expect to unravel the association of the nuclear envelope with telomere stability and its association with cancer. The work-packages that we propose include tasks which are designed as a logical sequence, planned to give results independently, and, at the same time, to produce an integrative picture of the implication of telomeres, replication stress and nuclear envelope in genome integrity. Given the established role of replication stress in cancer, and the open questions related to its mechanics, our data will contribute to the identification of cancer molecular players. We have decided to focus on lymphomagenesis because we have preliminary data on lymphomas, and to give a defined picture on a single cancer type. However, three elements chosen in this study represent models for larger interpretation schemes of mechanisms of tumorigenesis. Indeed, lymphomas model cancers affecting highly proliferating tissue. Secondly, telomeres are paradigmatic replication challenging sequences. Thirdly, the nuclear envelope connects our study to phenotypes related to aged cells, which have nuclear envelope defects. Moreover correction strategies for cancer require well-defined explanations of molecular drivers to create customized therapeutic approaches. This study will provide relevant results contributing to elucidating the molecular drivers linking replication stress and cancer Altogether, this suggests that this study can impact on cancer, and on basic knowledge, with a robustly positive success/risk ratio. Depending on the accorded grant we will develop one or more workpackages.
References of the entire project:
1 Tubbs A et al, Cell 2017
2 Gaillard H et al, Nat Rev Cancer,2015
3 Sfeir A et al, Cell 2009
4 Drosopoulos W et al, J Cell Biol 2013
5 Vannier J et al, Science 2013
6 Pinzaru A et al, Cell Reports 2016
7 Scherthan H et al, Mol Biol Cell 2000
8 Schmitt J et al, PNAS 2007
9 Link J et al, PLoS Genetics 2013
10 Bronshtein I et al, Nature Communications 2015
11 Crabbe L et al, Cell reports 2012
12 Gonzalez-Suarez I, Cell Cycle 2009
13 Gonzalo S, Adv Exp Med Biol 2014
14 Burla R et al, Nucleus, 2018
15 Scaffidi P, Misteli T, Science 2006
16 Burla R et al, PLoS genetics 2015
17 Cenci G et al, PLoS genetics 2015
18 Burla R et al, Open Biol 2016
19 La Torre M et al, Aging Cell 2018
20 Cerella C et al, EMBO J 2016
21 Pegoraro G et al, Nat Cell Biol, 2009
22 Capell B et al, PNAS 2005