Ricerc@Sapienza

The abundance of hTR, the telomerase RNA, is negatively regulated by the TGS1 hypermethylase, which converts the hTR 5' mono-methylguanosine cap to a trimethylguanosine cap. TGS1 loss results in an increase of hTR dosage, upregulation of telomerase activity and telomere elongation. We have also found that chemical inhibition of TGS1 by the SAM analog sinefungin, elicits phenotypes similar to those observed upon genetic loss of TGS1. We are currently testing if chemical inhibition of TGS1 may be beneficial for diseases caused by excessive telomere shortening, due to mutations in genes controlling telomerase homeostasis, such as dyskeratosis congenita (DC) and pulmonary fibrosis. In these disorders, the primary defect is shortened telomeres, which in turn cause exhaustion of stem cells renewal, resulting in tissue homeostasis failure at organism level. We will assay sinefungin and its analogs for their ability to restore telomere length in different cell types, carrying mutations in the PARN or DKC1 genes (found in patients affected by DC), with the objective of correcting their telomere shortening phenotype, thus improving their proliferation potential.
We will also explore the role of TGS1 in the DNA damage response. Our recent work suggests the hypothesis that TGS1 might cooperate with the Survival Motor Neuron protein (SMN) in preventing the accumulation of transcriptional stress in the genome and in particular at transcription termination regions. Both TGS1 and Smn physically interact with Topoisomerase 2, which prevents R-loops accumulation. To address the functional relationships between these protein in the maintenance of genome stability, we will perform studies on Drosophila mutants in which Tgs1, Smn and Top2 functions are specifically depleted in the eye imaginal discs by RNAi, and in parallel, experiments in CRISPR-cas9-derived HeLA cells, deficient for TGS1 and SMN.