Sulfoquinovosyl acylpropanediol (SQAP): Inhibition of poly(ADP-ribose) metabolism and enhanced cytotoxicity in homologous recombination repair-deficient Chinese hamster-derived cells.

Sulfoquinovosyl acylpropanediol (SQAP; a synthetic derivative of the sulfoglycolipid natural product sulfoquinovosyl acylglycerol, SQAG), has anti-tumor and radiosensitizing activities in tumor xenograft mouse models. Here, we have studied the PARP inhibitory activity of SQAP and synthetic lethality in BRCA2-deficient cells. In initial screening studies with DNA repair-deficient Chinese hamster ovary cells, homologous recombination repair-deficient cell lines showed increased sensitivity to SQAP, compared to wild-type cells or other DNA repair-deficient mutants. Chinese hamster lung V79 cells and the derivative cell lines V-C8 (BRCA2-deficient) and V-C8 + BRCA2 gene corrections were used to test the role of BRCA2 in SQAP cytotoxicity. The findings were confirmed in studies of the human colon cancer cell lines DLD-1 and its BRCA2-knockout derivative. SQAP inhibited the enzymes poly(ADP-ribose) polymerase (PARP) and poly(ADP-ribose) glycohydrolase (PARG). SQAP pretreatment decreased H2O2induced poly(ADP-ribose) formation in V79 cells. SQAP caused DNA double-strand breaks and chromosome aberrations in V79 BRCA2-mutated cells but did not affect cells in the G2 phase. We have demonstrated that SQAP induces synthetic lethality in BRCA2-deficient Chinese hamster-derived cells via its effects on poly(ADP-ribose) metabolism, motivating further examination of its therapeutic potential, especially against tumors that are deficient in homologous recombination repair due to mutations in BRCA2 or other genes.

Global analysis of the regulatory network structure of gene expression in Saccharomyces cerevisiae.

Gene expression in eukaryotic cells is controlled by the concerted action of various transcription factors. To help clarify these complex mechanisms, we attempted to develop a method for extracting maximal information regarding the transcriptional control pathways. To this end, we first analyzed the expression profiles of numerous transcription factors in yeast cells, under the assumption that the expression levels of these factors would be elevated under conditions in which the factors were active in the cells. Based on the results, we successfully categorized about 400 transcription factors into three groups based on their expression profiles. We then analyzed the effect of the loss of function of various induced transcription factors on the global expression profile to investigate the above-mentioned assumption of a correlation between transcription elevation and functional activity. By comparing the expression profiles of wild-type with those of disruption mutants using microarrays, we were able to detect a substantial number of relations between transcription factors and the genes they regulate. The results of these experiments suggested that our approach is useful for understanding the global transcriptional networks of eukaryotic cells, in which most genes are regulated in a temporal and conditional manner.