Page 190 - 2014 Printable Abstract Book
P. 190
PS3 SPACE RADIATION, RADIOTHERAPY, POST RADIATION
(PS3-01) A novel role for Rad51 in cellular response to clustered DNA lesions. Eiichiro Mori, MD; Fengtao
Su, PhD; David J. Chen, PhD; and Aroumougame Asaithamby, PhD; Department of Radiation Oncology,
University of Texas Southwestern Medical Center, Dallas, TX
Convincing evidence indicate that high-linear energy transfer (LET) ionizing radiation (IR) induced
complex DNA lesions are more difficult to repair than isolated DNA lesions induced by low-LET IR and, in
some instances, irreparable. This has been associated with the increased relative biological effectiveness
for cell killing, chromosomal aberrations, mutagenesis, and carcinogenesis in high-LET irradiated cells
compared to those treated with low-LET radiation. Though various DNA repair pathways have been
implicated in the processing of clustered DNA lesions, the exact role of Rad51-mediated homologous
recombination (HR) pathways in the suppression of genome instability in response to high-LET IR remains
unclear. To explore the contribution of Rad51 in cellular responses to clustered DNA lesions, we
established a tetracycline-inducible small-hairpin RNA-mediated Rad51 knock-down human cell line.
Using this cell line, we noticed that the Rad51-deficient cells were highly sensitive to Fe-particles
irradiation as compared with low-LET γ-irradiation. Further, using a novel cell line that differentiates cells
in different phases of the cell cycle, we found that the S/G2-phase cells lacking Rad51 lost their ability to
repair a major fraction of clustered-DSBs. In contrast to control cells, Rad51-deficient cells were arrested
in S-phase, but not in G2-phase, for a prolonged period after the Fe-particles irradiation, and this
correlated well with the DNA-damage response signaling. Furthermore, Rad51-deficient cells were not
only defective in clustered-DSBs repair, but also defective in replication fork recovery in response to Fe-
particles irradiation. Notably, we noticed that Rad51 was important for the protection of newly replicated
genome from MRE11-mediated degradation in response to clustered DNA lesions. Significantly, Fe-
particles irradiated Rad51-deficient cells exhibited elevated levels of gross-chromosomal, including
chromatid- and chromosome-type aberrations. Thus, difficulties associated with clustered DNA damage
repair together with defective nascent DNA strand protection in Rad51-deficient human cells appear to
promote genome instability that may lead to carcinogenesis. Acknowledgements: This work is supported
by National Aeronautics and Space Administration, USA.
(PS3-02) Biological and metabolic response in STS-135 space-flown mouse skin. Xiao Wen Mao, MD ,
4
1
2
3
Michael J. Pecaut, PhD ; Louis S. Stodieck, PhD ; Virginia L. Ferguson, PhD ; Ted A. Bateman, PhD ; Mary
1
1
5
Bouxsein, PhD ; and Daila S. Gridley, PhD; Loma Linda University, Loma Linda, CA , Bioserve Space
2
Technology, University of Colorado, Boulder, CO , BioServe Space Technology, University of Colorado,
3
4
Boulder, CO , University of North Carolina at Chapel Hill, Chapel Hill, NC , and Harvard Medical School,
5
Boston, MA
There is evidence that space flight condition-induced biological damage that is associated with
increased oxidative stress. Strong links have been shown between oxidative stress and extracellular matrix
(ECM) remodeling. To explore oxidation and antioxidant response in mouse skin tissue, changes in
expression of genes implicated in oxidative stress and in ECM remodeling and selected protein expression
profiles were examined after spacefight. The metabolic effects of space flight in the glutathione
metabolism and redox homeostasis of skin tissues were also characterized. STS-135 was launched at the
Kennedy Space Center (KSC) on a 13 day mission in July of 2011. Female C57BL/6 mice were flown in the
Space Shuttle Atlantis (STS-135) using animal enclosure modules (AEMs). Within 3-5 hours of landing, the
188 | P a g e
(PS3-01) A novel role for Rad51 in cellular response to clustered DNA lesions. Eiichiro Mori, MD; Fengtao
Su, PhD; David J. Chen, PhD; and Aroumougame Asaithamby, PhD; Department of Radiation Oncology,
University of Texas Southwestern Medical Center, Dallas, TX
Convincing evidence indicate that high-linear energy transfer (LET) ionizing radiation (IR) induced
complex DNA lesions are more difficult to repair than isolated DNA lesions induced by low-LET IR and, in
some instances, irreparable. This has been associated with the increased relative biological effectiveness
for cell killing, chromosomal aberrations, mutagenesis, and carcinogenesis in high-LET irradiated cells
compared to those treated with low-LET radiation. Though various DNA repair pathways have been
implicated in the processing of clustered DNA lesions, the exact role of Rad51-mediated homologous
recombination (HR) pathways in the suppression of genome instability in response to high-LET IR remains
unclear. To explore the contribution of Rad51 in cellular responses to clustered DNA lesions, we
established a tetracycline-inducible small-hairpin RNA-mediated Rad51 knock-down human cell line.
Using this cell line, we noticed that the Rad51-deficient cells were highly sensitive to Fe-particles
irradiation as compared with low-LET γ-irradiation. Further, using a novel cell line that differentiates cells
in different phases of the cell cycle, we found that the S/G2-phase cells lacking Rad51 lost their ability to
repair a major fraction of clustered-DSBs. In contrast to control cells, Rad51-deficient cells were arrested
in S-phase, but not in G2-phase, for a prolonged period after the Fe-particles irradiation, and this
correlated well with the DNA-damage response signaling. Furthermore, Rad51-deficient cells were not
only defective in clustered-DSBs repair, but also defective in replication fork recovery in response to Fe-
particles irradiation. Notably, we noticed that Rad51 was important for the protection of newly replicated
genome from MRE11-mediated degradation in response to clustered DNA lesions. Significantly, Fe-
particles irradiated Rad51-deficient cells exhibited elevated levels of gross-chromosomal, including
chromatid- and chromosome-type aberrations. Thus, difficulties associated with clustered DNA damage
repair together with defective nascent DNA strand protection in Rad51-deficient human cells appear to
promote genome instability that may lead to carcinogenesis. Acknowledgements: This work is supported
by National Aeronautics and Space Administration, USA.
(PS3-02) Biological and metabolic response in STS-135 space-flown mouse skin. Xiao Wen Mao, MD ,
4
1
2
3
Michael J. Pecaut, PhD ; Louis S. Stodieck, PhD ; Virginia L. Ferguson, PhD ; Ted A. Bateman, PhD ; Mary
1
1
5
Bouxsein, PhD ; and Daila S. Gridley, PhD; Loma Linda University, Loma Linda, CA , Bioserve Space
2
Technology, University of Colorado, Boulder, CO , BioServe Space Technology, University of Colorado,
3
4
Boulder, CO , University of North Carolina at Chapel Hill, Chapel Hill, NC , and Harvard Medical School,
5
Boston, MA
There is evidence that space flight condition-induced biological damage that is associated with
increased oxidative stress. Strong links have been shown between oxidative stress and extracellular matrix
(ECM) remodeling. To explore oxidation and antioxidant response in mouse skin tissue, changes in
expression of genes implicated in oxidative stress and in ECM remodeling and selected protein expression
profiles were examined after spacefight. The metabolic effects of space flight in the glutathione
metabolism and redox homeostasis of skin tissues were also characterized. STS-135 was launched at the
Kennedy Space Center (KSC) on a 13 day mission in July of 2011. Female C57BL/6 mice were flown in the
Space Shuttle Atlantis (STS-135) using animal enclosure modules (AEMs). Within 3-5 hours of landing, the
188 | P a g e
