Titolo della tesi: Yeast decapping mutants as model systems for ageing and autophagy
The S. cerevisiae yeast has been successfully established over time as a useful eukaryotic model for
the study of various physiological and pathological cellular processes. Among these, cellular
ageing plays a role of great interest, as it is the result of the occurrence of different pathways and
molecular changes which can be challenging to study in a more complex model system. In
previous studies it has been shown that the mutant strain for the essential gene LSM4, whose
protein product is involved in the degradation of messenger RNAs, shows premature markers of
aged cells and shorter life span due to the uncontrolled accumulation of RNA in the cytoplasm. In
this context, generally the survival mechanism of choice of the cell population turns out to be
autophagy and, if this is not sufficient, the consequent triggered process is the regulated cell death.
It has been demonstrated the involvement of LSM complex in autophagy regulation and in the
case of the LSM4 mutant, a gene involved in the biosynthesis of phospholipids and membranes
necessary for the autophagic process, NEM1, has a positive effect on the life span of the strain.
Starting from this, in the present work we demonstrate that in the mutant strain the activation of
autophagy due to restriction of nutrients or during chronological ageing is compromised, with an
accumulation of cytoplasmic autophagosomal structures, and that the increase in viability u nder
calorie restriction is probably dependent on a change in RNAs metabolism or in the activation of
an alternative autophagic pathway . Furthermore, we created a reporter system comprising the
truncated form of LSM4 and the GFP protein at genome level using the CRISPR /Cas9 system,
which shows the phenotypic markers of premature aged cells as well.