1) Long Interspersed Nuclear elements (LINE) are transposable
elements so abundant to represent large portions of the human
genome (about 20%). They amplify themselves, inserting copies in
new genomic locations, by a RNA-mediated retrotransposition
process. Their mobility is generally repressed in most
differentiated somatic cells, but it can be activated in several
conditions. Until now the factors involved in LINE activation are
still little known. Aim of this study is to gain understanding on
how retrotransposition is regulated, using a L1 engineering element
in an in vitro retrotransposition assay.
2) Exposure to extremely low frequency magnetic fields (ELF-MF)
is ubiquitous in industrialized countries. Until now, conclusive
results on ELF-MF biological and health effects have not yet been
obtained because of the high number of parameters that have to be
considered. Aim of this study is to investigate on the biological
effects, including genotoxicity, of ELF-MFs with different
physical characteristics.
1) LINE elements belong to the non-LTR retrotransposon class and
amplify themselves by a retrotransposition process consisting of
several steps: L1 RNA transcription, transport to the cytoplasm,
translation of its two ORFs, formation of ribonucleic particle,
return to nucleus, reverse transcription and integration of
retrotranscripts in a new genomic location by a molecular mechanism
termed target-site primed reverse transcription (TPRT). Although
the majority of human LINEs are defective, about 100 functional
elements have been estimated. Their mobility can give arise to
insertional mutagenesis, transduction, genomic deletions, thus
modifying genome structure and function. This could on one hand
contribute to genome evolution, on the other one cause a variety of
diseases. Active in gem line cells, LINEs are generally repressed
in most somatic cells. Until now, multiple factors that limit L1
retrotransposition at different molecular steps have been
identified, including methylation, RNA interference, APOBEC3
proteins, L1 ribonucleoprotein sequestering in stress granules.
Recently it has been observed, using an in vitro
retrotransposition, that L1 retrotransposition can occur in some
somatic cells, such as human embryonic, neuronal precursor, tumour
cells; in addition several chemical and physical agents, including
UV, heavy metals, benzo(a)pyrene, have been reported to induce
retrotransposition. The cellular factors determining these LINE
activations are still little known. The aim of the present research
is to gain understanding on how retrotransposition is regulated,
using a L1 engineering element in an in vitro
retrotransposition assay. The study addresses two aspects. The
first concerns L1 regulation in relationship with neural cell
differentiation. A neuroblastoma cell line ha been chosen as a
model because it is easily induced to differentiate in
vitro towards neural phenotype. This cell line has been
observed to be able to support L1 retrotransposition, though with a
low frequency. Analysis will be performed in order to verify
whether and how differentiation can influence L1 mobility, which
cellular factors and which steps of retrotransposition process can
be involved. The second aspect that will be addressed deals with
those environmental factors able to influence L1
retrotransposition. The effect of several chemical and physical
agents, including magnetic fields, temperature shocks,
oxidants, will be investigated studying the signalling
pathways involved.
2) Extremely low frequency magnetic fields (ELF-MF) can
influence cell physiology so that they are used as therapeutic
agents. However a clear picture is not yet emerging because of the
high number of parameters that have to be considered. ELF-MF
biological effects critically depend on exposure duration, signal
characteristics, magnitude of magnetic induction, hence the results
obtained by different laboratories are often not comparable. The
aim of this study is to investigate the influence of ELF-MFs with
different physical characterictics on some biological end points
(proliferation index, viability, heat shock and differentiation
marker expression) in several human cell types. In addition
possible genotoxic effects will be evaluated assessing both single-
and double-strand DNA break induction.
