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Title
MOLECULAR FUNCTIONS OF THE CHROMATIN REMODELER FUN30
Faculty Advisor
Dr. Ahmed H. Hassan Al Marzouqi
Defense Date
4 January 2017
Abstract
Many studies have identified conserved ATP-dependent chromatin remodeling complexes whose functions
are to modulate DNA access by relieving chromatin-mediated repression. We have previously characterized
Fun30 in Saccharomyces cerevisiae as a homodimer with ATP-dependent chromatin remodeling activity.
Other studies have shown that Fun30 plays a role in maintaining the silenced state of subtelomeric and
centromeric chromosomal regions. Fun30 has also been shown to play an important role in DNA damage
repair by facilitating long range resection of DNA in Double Strand Breaks. This thesis was focuses on
understanding the mechanisms by which Fun30 is involved in DNA damage repair. Results presented here
show that Fun30 can anneal complementary strands of DNA that is facilitated by ATP hydrolysis and
a helicase activity in the presence of trap DNA. In addition, Fun30 was found to be able to relax both
negatively and positively supercoiled DNA in an ATP-independent manner and cleave a 3’ overhang in
a forked DNA duplex or a duplex that has a protruding 3’. Annealing and 3’ flap endonuclease activities
of Fun30 suggest a mechanism by which Fun30 can facilitates double strand break repair by the Single
Strand Annealing pathway, while a potential helicase activity can facilitate Synthesis Depended Strand
Annealing and as a result reduce the generation of recombination intermediates. Moreover, employing
in vivo approaches, we show that Fun30 genetically interacts with the Mus81 nuclease upon chronic
treatment with chemicals that stall the replication fork, suggesting that Fun30 deletion might lead to the
accumulation of toxic recombination intermediates that are difficult to resolve in the absence of Mus81.
We also found that Fun30 deletion affects the cell cycle progression of cells lacking TopI, without affecting
the viability of the cells. This might explain a function for Fun30 in facilitating the progression of the cell
cycle in the presence of torsional stress which can be induced by TopI deletion. Moreover, we found that
Fun30 is not involved in removing camptothecin induced TopI/DNA complexes since no genetic interaction
between Tdp1 and Fun30 was observed. Furthermore, we show that Fun30 genetically interacts with Asf1
under DNA damaging conditions, suggesting that Fun30 is required in the absence of Asf1. Finally, couple
of models are proposed that explain how Fun30 annealing and nuclease activities may be important in
the Single Strand Annealing pathway and how Fun30 helicase activity might be used to reduce the level of
toxic recombination intermediates and thus maintain genomic stability, which if compromised could lead
to cancer or other diseases.
Dissertation
ZEINA SALIM AL-NATOUR
Department of Biochemistry and Molecular Biology
College of Medicine and Heath Sciences