Page 117 - 2014 Printable Abstract Book
P. 117
few studies addressing the role of glial cells, we had focused our first NASA grant proposal on identifying
the major DNA repair pathways induced by oxidative stress due to high atomic number (Z) and energy
(HZE) radiation in glial cells. Ionizing radiation (IR) causes degeneration of myelin, the insulating sheaths
of neuronal axons, leading to neurological impairment. Recent data with lower doses of 600 MeV/n of
56Fe particle radiation not only show dose-dependent decrease in viable neurons (like X-rays), but also
reveal an adverse effect on astrocytes and OL progenitor cells (OPC). However, with higher doses, there
was an increase in the proportion of OPC-derived astrocytes, suggesting astrocytosis. Thus, astronauts
exposed to protons and HZE radiation may risk adverse effects during their missions as well as latent
health effects. Moreover, patients undergoing fractionated radiotherapy show higher DNA repair activity
in their normal cells as compared to their tumor cells. Because base excision DNA repair (BER) is a pathway
up-regulated in response to oxidative stress by low-LET radiation, it is important to determine how high-
LET-induced BER affects the fate of OPC. BER is even more important in mitochondria, the predominant
sites of oxidative metabolism, where other DNA repair pathways are more limiting or absent. Our current
studies show significant induction of the central BER enzyme apurinic endonuclease-1 (APE1) in rat glial
progenitor cell (GPC) line CG-4 as well as in OPC of rat spinal cords white matter section, with dose
fractionation. Also fractionation of HZE and Protons increased demyelination, neuro inflammation and
cognitive deficits. In this project, we are determining the mechanism of latent cognitive changes from HZE
particle and proton exposures with development of APE1 and other DNA repair proteins, as radiation bio
markers to quantify these changes and predict radiation risks to CNS. This work was supported by NASA
HRP program grants NNX11AO89G and NNAX13AD74G to MN with partial salary support from NASA grant
NNX13AJO1G to LH (for MP and MN).
(PS1-26) Regulation of DNA repair system by nuclear structure proteins. Ning-Ang Liu; Jiying Sun; and
Satoshi Tashiro, Department of Cellular Biology, Research Institute for Radiation Biology and Medicine,
Hiroshima University, Hiroshima City, Japan
DNA repair plays an important role in keeping genomic integrity. Recent advances in the research
field of DNA repair have revealed the role of chromatin reorganization in the regulation of DNA damage
response. However, how proteins associated with nuclear architectures are involved in the regulation of
DNA repair is unclear. To investigate the role of nuclear architectures in DNA repair, we searched proteins
associated with nuclear structures in the RAD51 protein complex. RAD51 is a key player in homologous
recombinational repair (HR) of DNA double strand breaks (DSBs). We identified Lamin B1, a nuclear lamina
protein, in the RAD51 protein complex obtained from both irradiated and non-irradiated human cells. The
B-type lamins are important structural determinant for the nuclear envelope as a whole, which play
important roles in the structural organization and function of the eukaryotic cell nucleus. The depletion
of Lamin B1 lead to a significant decrease in RAD51 protein levels of human cells after ionizing radiation
(IR). This finding suggests that Lamin B1 is involved in the regulation of RAD51 function following DNA
damage. We conjectured that this Lamin B1 depletion would impair RAD51 mediated HR repair after IR.
To further explore this notion, we examined the role of Lamin B1 in the RAD51 focus formation.
Immunofluorescence staining analysis using anti-RAD51 antibody revealed that the radiation-induced
focus formation of RAD51 was significantly repressed in Lamin B1 deficient cells compared to control cells.
On the other hand, Sister Chromatid Exchange (SCE), which is mediated by HR, was significantly decreased
by the depletion of Lamin B1. Taken together, these findings strongly suggest that Lamin B1 is involved in
HR repair by regulating RAD51 function after IR.
115 | P a g e
the major DNA repair pathways induced by oxidative stress due to high atomic number (Z) and energy
(HZE) radiation in glial cells. Ionizing radiation (IR) causes degeneration of myelin, the insulating sheaths
of neuronal axons, leading to neurological impairment. Recent data with lower doses of 600 MeV/n of
56Fe particle radiation not only show dose-dependent decrease in viable neurons (like X-rays), but also
reveal an adverse effect on astrocytes and OL progenitor cells (OPC). However, with higher doses, there
was an increase in the proportion of OPC-derived astrocytes, suggesting astrocytosis. Thus, astronauts
exposed to protons and HZE radiation may risk adverse effects during their missions as well as latent
health effects. Moreover, patients undergoing fractionated radiotherapy show higher DNA repair activity
in their normal cells as compared to their tumor cells. Because base excision DNA repair (BER) is a pathway
up-regulated in response to oxidative stress by low-LET radiation, it is important to determine how high-
LET-induced BER affects the fate of OPC. BER is even more important in mitochondria, the predominant
sites of oxidative metabolism, where other DNA repair pathways are more limiting or absent. Our current
studies show significant induction of the central BER enzyme apurinic endonuclease-1 (APE1) in rat glial
progenitor cell (GPC) line CG-4 as well as in OPC of rat spinal cords white matter section, with dose
fractionation. Also fractionation of HZE and Protons increased demyelination, neuro inflammation and
cognitive deficits. In this project, we are determining the mechanism of latent cognitive changes from HZE
particle and proton exposures with development of APE1 and other DNA repair proteins, as radiation bio
markers to quantify these changes and predict radiation risks to CNS. This work was supported by NASA
HRP program grants NNX11AO89G and NNAX13AD74G to MN with partial salary support from NASA grant
NNX13AJO1G to LH (for MP and MN).
(PS1-26) Regulation of DNA repair system by nuclear structure proteins. Ning-Ang Liu; Jiying Sun; and
Satoshi Tashiro, Department of Cellular Biology, Research Institute for Radiation Biology and Medicine,
Hiroshima University, Hiroshima City, Japan
DNA repair plays an important role in keeping genomic integrity. Recent advances in the research
field of DNA repair have revealed the role of chromatin reorganization in the regulation of DNA damage
response. However, how proteins associated with nuclear architectures are involved in the regulation of
DNA repair is unclear. To investigate the role of nuclear architectures in DNA repair, we searched proteins
associated with nuclear structures in the RAD51 protein complex. RAD51 is a key player in homologous
recombinational repair (HR) of DNA double strand breaks (DSBs). We identified Lamin B1, a nuclear lamina
protein, in the RAD51 protein complex obtained from both irradiated and non-irradiated human cells. The
B-type lamins are important structural determinant for the nuclear envelope as a whole, which play
important roles in the structural organization and function of the eukaryotic cell nucleus. The depletion
of Lamin B1 lead to a significant decrease in RAD51 protein levels of human cells after ionizing radiation
(IR). This finding suggests that Lamin B1 is involved in the regulation of RAD51 function following DNA
damage. We conjectured that this Lamin B1 depletion would impair RAD51 mediated HR repair after IR.
To further explore this notion, we examined the role of Lamin B1 in the RAD51 focus formation.
Immunofluorescence staining analysis using anti-RAD51 antibody revealed that the radiation-induced
focus formation of RAD51 was significantly repressed in Lamin B1 deficient cells compared to control cells.
On the other hand, Sister Chromatid Exchange (SCE), which is mediated by HR, was significantly decreased
by the depletion of Lamin B1. Taken together, these findings strongly suggest that Lamin B1 is involved in
HR repair by regulating RAD51 function after IR.
115 | P a g e
