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1 June 2007 The Delayed Quinacrine Mustard Fluorescence from the C-blocks of Apodemus argenteus Is Due to the Introduction of Nicks into the DNA
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Abstract

“Delayed QM-fluorescence” refers to the unusual kinetics of fluorescence from most of the C-heterochromatic regions of the chromosomes of the small Japanese field mouse Apodemus argenteus. When stained with quinacrine mustard (QM-stained), these C-heterochromatic regions emit weak fluorescence immediately after exposure to blue light (BL); they emit bright fluorescence within a few minutes; and the intensity of the fluorescence gradually decreases after maximum fluorescence has been recorded. To elucidate the mechanism of this phenomenon, we used acridine orange staining (AO-staining) and a modified version of the in situ nick-translation method. Focusing on the large C-heterochromatic region (C-block) of the X chromosome, we noted that AO-stained C-blocks emitted greenish fluorescence, while QM-stained and BL-exposed (QM-BL-processed) C-blocks emitted reddish fluorescence upon AO-staining after removal of QM. These findings suggested that the C-block DNA of A. argenteus might undergo a structural change, such as strand breaks, during QM-BL processing. Application of the modified in situ nick-translation method revealed the generation of an appreciable number of nicks in the C-block DNA by QM-BL processing. No such nick formation was observed in the C-blocks of three other mammalian species: Apodemus peninsulae, Microtus montebelli, and Urotrichus talpoides. Our findings support the hypothesis that nick formation due to exposure to BL might play a primary role in inducing delayed QM-fluorescence in the C-blocks of A. argenteus. On the basis of the present and earlier findings, we propose a probable mechanism for delayed QM-fluorescence in A. argenteus chromosomes.

Michiko Inuma, Yoshitaka Obara, and Masaki Kuro-o "The Delayed Quinacrine Mustard Fluorescence from the C-blocks of Apodemus argenteus Is Due to the Introduction of Nicks into the DNA," Zoological Science 24(6), 588-595, (1 June 2007). https://doi.org/10.2108/zsj.24.588
Received: 9 September 2006; Accepted: 1 January 2007; Published: 1 June 2007
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