Indiana University-Purdue University Indianapolis (IUPUI) / Fanconi Anemia (FA), a chromosomal instability syndrome, is characterized by
bone marrow failure, genetic malformations, and predisposition to malignancies
like acute myeloid leukemia (AML) and solid tumors. FA is caused by germline
bi-allelic mutations in one of 21 known FA pathway genes and somatic mutations
in FA genes are also found in a variety of sporadic cancers. Recently, numerous
reports have discovered that the protective function of the FA pathway extends
beyond its canonical role in regulation of DNA repair in interphase. In particular,
the FA pathway has been shown to function in essential mitotic processes
including spindle assembly checkpoint (SAC), cytokinesis, and centrosome
maintenance.
Understanding of the mechanistic origins of genomic instability leading to
carcinogenesis and bone marrow failure has important scientific and clinical
implications. To this end, using a micronucleus assay, we showed that both
interphase DNA damage and mitotic errors contribute to genomic instability in FA
ex vivo and in vivo. Functional studies of primary FA patient cells coupled with
super-resolution microscopy revealed that FANCA is important for centrosome dependent spindle assembly supporting the protective role of FA pathway in
mitotic processes.
Furthermore, we dissected the interactions between the FA pathway and cellular
kinase networks by employing a synthetic lethality sh-RNA screen targeting all
human kinases. We mapped kinases that were synthetically lethal upon loss of
FANCA, particularly those involved in highly conserved signal transduction
pathways governing proliferation and cell cycle homeostasis. We mechanistically
show that loss of FANCA, the most abundant FA subtype, results in in premature
degradation of the mitotic kinase BUBR1 and faster mitotic exit. We further
demonstrate that FANCA is important for PCAF-dependent acetylation of BUBR1
to prevent its premature degradation.
Our results deepen our understanding of the molecular functions of the FA
pathway in mitosis and uncover a mechanistic connection between FANCA and
SAC phosphosignaling networks. These findings support the notion that further
weakening the SAC through targeting kinases like BUBR1 in FA-deficient
cancers may prove to be a rational therapeutic strategy.
| Identifer | oai:union.ndltd.org:IUPUI/oai:scholarworks.iupui.edu:1805/13850 |
| Date | 22 June 2017 |
| Creators | Abdul Sater, Zahi Abass |
| Contributors | Nalepa, Grzegorz, Clapp, Wade, Goebl, Mark, Wek, Ronald |
| Source Sets | Indiana University-Purdue University Indianapolis |
| Language | en_US |
| Detected Language | English |
| Type | Dissertation |
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