of the Max - MDC

Mobile DNA
Zsuzsanna Izsvák
DNA transposons are mobile genes transposing with low
intrinsic activity. These elements are self-regulated and
interact with cellular host factors without producing serious
levels of genetic damage. Transposons offer a new model to
study DNA recombination in higher organism, as well as hostparasite
interaction. Transposons are also natural gene delivery
vehicles that are being developed as genetic tools. Our laboratory
is following the strategy of understanding the mechanism
of transposition and its regulation and translate this knowledge
to derive transposon-based genetic tools for genome manipulation
or for gene therapy.
Checkpoint controls in Sleeping Beauty element
(SB) transposition
Diana Pryputniewicz
Our understanding the way of how eukaryotic recombinases
are working is still mostly based on assuming analogies to
bacterial transposons. Besides the basic chemical reaction,
the different elements have a variety of “built-in” regulatory
mechanisms, often involving host factors, to provide
specificity to the transposition reaction. The main function
of a regulation is to impose “quality control” on transposition
in the form of regulatory checkpoints, at which certain
molecular requirements have to be fulfilled for the transpositional
reaction to proceed. The role of these regulatory
checkpoints is to avoid accumulation of incorrect reaction
products in genomes, possessing a threat of genome instability
associated by transposition. Our ultimate goal is to
reconstruct the entire transposition process of the SB
in vitro, and to decipher the checkpoint controls of the
reaction. A fascinating question is the differential regulation
of transposition and the transposition derived V(D)J
recombination.
Recombination and DNA repair
Yongming Wang
Cellular mechanisms that are directly involved in repairing
transposition-inflicted DNA lesions or can attenuate DNA
damage should have crucial role in establishing stable hosttransposon
co-existence. Our results suggest that DNA damage
repair of lesions generated by transposition are differently
regulated from any other repair process. This differential
regulation manifests in actively influencing the
accessibility of host repair factors to the DNA lesions generated
by transposition. SB transposon takes advantage of the
cellular repair machinery and/or during DNA replication to
amplify their own genome. This process is active in germinal,
but strongly inhibited in somatic cells.
Transposition and stress/developmental
signaling
David Grzela, Anantharam Deveraj
Transposons occupy a significant portion of our genomes.
However, the vast majority of transposons remain silent due
to accumulated mutations in their genomes. The transposition
of the few, active copies is strongly regulated, but this
control is sensitive to environmental stress. Our preliminary
results show that transposons might exist in a “latent” form
in the genome and are able to sense developmental and
environmental changes and manipulate stress signaling.
Finding the active copy of RAT-IAP endogenous
retrovirus
Yongming Wang
The endogenous retrovirus, Rat-IAP was repeatedly demonstrated
to influence the expression of rat genes, without
knowing the active copy. A phenotype of hypodactyly in rat
was associated with a recent retrotransposition event. We
have identified an “active” copy of an IAP-type endogenous
retroelement in the rat genome, and showed that the element
is active in retrotransposition. The transpositionally
active copy has an intact env gene, so element might be
capable of infection.
Isolating hyperactive transposase versions by
directed evolution.
Lajos Mátés
It is widely believed that naturally occurring transposons
have not been selected for the highest possible activity, and
are strongly downregulated to avoid insertional inactivation
of essential genes. Using DNA shuffling technology combined
with molecular evolutionary approaches, we were able
to find a special combination of synergistic mutations that
resulted in a significant, ∼100-fold increase in transposase
activity in SB. The 100-fold hyperactive SB system
58 Cardiovascular and Metabolic Disease Research