DNA end protection is fundamental for the long-term preservation of the genome. In
vertebrates the Shelterin protein complex protects telomeric DNA ends, thereby contributing
to the maintenance of genome integrity. In the Drosophila genus, this function is
thought to be performed by the Terminin complex, an assembly of fast-evolving subunits.
Considering that DNA end protection is fundamental for successful genome replication,
the accelerated evolution of Terminin subunits is counterintuitive, as conservation
is supposed to maintain the assembly and concerted function of the interacting partners.
This problem extends over Drosophila telomere biology and provides insight into the
evolution of protein assemblies. In order to learn more about the mechanistic details
of this phenomenon we have investigated the intra- and interspecies assemblies of
Verrocchio and Modigliani, two Terminin subunits using in vitro assays. Based on our
results and on homology-based three-dimensional models for Ver and Moi, we conclude
that both proteins contain Ob-fold and contribute to the ssDNA binding of the Terminin
complex. We propose that the preservation of Ver function is achieved by conservation
of specific amino acids responsible for folding or localized in interacting surfaces.
We also provide here the first evidence on Moi DNA binding.
