| Non-Scientific Abstract Inside cells, DNA is packaged in strands known
as chromosomes.When cells divide, chromosomes duplicate, providing each new cell with a set of
chromosomes. During duplication, chromosomes inevitably grow shorter at the ends, due to the method
by which they are copied. The loss of important information is prevented by the presence of extra
DNA, called telomeres, at the ends of chromosomes. The telomeres in fruitflies are unique because
they are formed by a process that is different from that in other organisms.Moreover, certain
sections of fruitfly telomeres are not read to make proteins, yet they are present in all
fruitflies. This suggests that such regions are important to the cell. The purpose of this study
was to discover proteins that bind to one of these regions, Duplicate (Dup). Studies were conducted
by introducing the Dup region into yeast cells and then expressing fruitfly proteins in these
cells. Tests yielded 82 yeast cells containing proteins that might bind the Dup region, and these
cells will be studied further. Identifying proteins that bind Dup may help reveal other roles
telomeres play in the cell. Moreover, finding such proteins may reveal how the the method of
telomere formation in fruitflies is evolutionarily related to the method used by other organisms.
Abstract
While most organisms synthesize their telomeres by using the reverse transcriptase enzyme
telomerase, Drosophila caps its chromosome ends by the repeated transposition of two non-LTR
retrotransposons: HeT-A and TART.Unlike other retrotransposons, HeT-A and TART are found only at
the telomeres, and both possess exceptionally long untranslated regions. Certain A-rich regions in
HeT-A¹s 3¹ untranslated region, in particular, have been found in all HeT-A elements, suggesting
that these regions may be involved in binding proteins. To identify proteins that bind one of these
A-rich regions,Duplicate (Dup), a yeast one-hybrid screen was carried out.The Dup region was placed
upstream of a reporter gene, and the construct was integrated into the yeast genome. Potential
Dup-binding proteins were introduced into the cell, in the form of a cDNA library encoding
Drosophila proteins. Positive protein-DNA interactions were detected by the activation of the
reporter gene. Transformation with the cDNA library yielded 82 possible interactors,which will be
characterized further. It is hoped that identifying proteins that bind Dup will increase our
understanding of the roles played by telomeres in the cell, as well as help clarify the
evolutionary relationship between retrotransposons and retroviruses. |
