Ricerc@Sapienza

Telomeres are very challenging genomic regions for the replication complex progress due to the their specific features; indeed the presence of heterochromatin, of secondary structures such as G-quadruplex and T-loop, TERRA transcription, as well as telomere compaction and telomere attachment to the nuclear envelope can be sources of endogenous blocks for replication forks. The shelterin TRF1 plays a key role in ensuring proper telomere replication; in its absence were observed the formation of telomeric aberration linked to replication impairment, as fragile telomeres. It likely acts mainly by recruiting specific factors to telomeres in S-phase, such as helicases BLM and RTEL1, that unwind telomeric secondary structure to allow replication fork complex passage. However the precise mechanism of action is still elusive and probably other factors remain to be discovered.
AKTIP is a telomeric protein that interacts with shelterins TRF2 and TRF1 and its important for proper telomere replication. Indeed its absence triggers the formation of aberrant telomeres, in particular fragile telomeres and sister telomere association, and affects the incorporation of BrdU at telomeres, both indicative of replication defects. This replication impairment induces the DNA damage response activation culminating in senescence induction in primary cells. AKTIP also interacts with replisome components RPA70 and PCNA. Even though AKTIP is clearly involved in telomere replication, its mechanism of action remains elusive. The aim of this project is investigate how AKTIP acts on telomere replication moving from the hypothesis that AKTIP forms a complex with shelterin TRF1 at telomeres in S-phase that contributes to correct recruitment of DNA helicases, BLM, WRN and RTEL1, at telomeres and to fork complex stabilization at these genomic regions. This study could also give insight in the definition of molecular mechanism of telomere replication, which is essential for genome integrity maintenance