Multi-copy suppression of the lethality of essential checkpoint genes by CYC8 in Saccharomyces cerevisiae

초록

CYC8 (CRT8) was originally identified as a mutant that express high levels of RNR3 in the absence of DNA damaging agents. It forms a complex with Tup1 and acts as a general transcriptional co-repressor. It also acts as part of a transcriptional co-activator complex that recruits the SWI/SNF and SAGA complexes to promoters. Rad53 is an essential checkpoint kinase that plays a central role in cell cycle arrest at all checkpoints. It also functions in transcriptional activation in response to DNA damage. RNR, the key enzyme in the maintenance and regulation of dNTP biosynthesis, is one of the target genes for transcriptional control by Rad53. In this study, we screened multi-copy suppressor genes that suppress the hydroxyurea sensitivity of rad53 mutant, and identified CYC8 as a candidate gene. Overexpression of CYC8 by a multi-copy plasmid suppressed the lethality of rad53 null-mutation. The yeast cells transformed with this plasmid showed lower dNTP levels than were observed in the cells with control plasmid. The possible mechanism of multi-copy suppression by CYC8 was discussed on the basis of these observations. (This work supported by grant R01-2007-000-20380-0 from KOSEF)