Role of LET and chromatin structure on chromosomal inversion in CHO10B2 cells.
BACKGROUND
In this study we evaluated the effect of linear energy transfer (LET) and chromatin structure on the induction of chromosomal inversion. High LET radiation causes more complex DNA damage than low LET radiation; this "dirty" damage is more difficult to repair and may result in an increase in inversion formation. CHO10B2 cells synchronized in either G1 or M phase were exposed 0, 1, or 2 Gy of 5 mm Al and Cu filters at 200 kVp and 20 mA X-rays or 500 MeV/nucleon of initial energy and 200 keV/μ m Fe ion radiation. In order to increase the sensitivity of prior techniques used to study inversions, we modified the more traditional Giemsa plus fluorescence technique so that cells were only allowed to incorporate BrdU for a single cycle verses 2 cycles. The BrdU incorporated DNA strand was labeled using a BrdU antibody and an Alexa Fluor 488 probe. This modified technique allowed us to observe inversions smaller than 0.6 megabases (Mb).


RESULTS
In this study we have shown that high LET radiation induces significantly more inversions in G1 cells than in M phase cells. Additionally, we have shown that the sizes of the induced inversions not only differ between Fe ion and X-rays, but also between G1 and M phase cells exposed to Fe ions.


CONCLUSIONS
We have effectively shown that both radiation quality and chromosome structure interact to alter not only the number of inversions induced, but also the size of the inversions.
Ian M
IM
Cartwright
Matthew D
MD
Genet
Akira
A
Fujimori
Department of Environmental and Radiological Health Sciences, Colorado State University, 1618 Campus Delivery, Fort Collins 80523, USA. takamitsu.kato@colostate.edu.
Takamitsu A
TA
Kato