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RNR3 Gene Expression is Regulated by WEB2 Gene in S Checkpoint Pathway of S.cerevisiae
Xin-Ming Li1, Li-Guang Sun*, Ping Liu, Yue Fu, Fu-Sheng Bai2, Zhong-Xin Xuan
Department of Biochemistry and Molecular Biology, 1Department of Microbiology and Parasitology, China Medical University, Shenyang 110001, China; 2Depatrment of Neurology, Liaoning Provincial Jinqiu Hospital, Shenyang 110016, China
Abstract: Previous works suggest the role of WEB2 in S checkpoint regulation， it is necessary to make sure its location and interactions with other checkpoint genes in this signal transduction pathway. RNR3 gene is an important effector at the end of this pathway. The transcription of RNR3 gene is induced in response to DNA damage or DNA replication block. So we detect if WEB2 gene involves in RNR3 induction .The induction of RNR3 gene was investigated in S.cerevisiae using RNR3-LacZ fusion plasmid. Gene induction was monitored by measuring the b-galactosidase activity. When WEB2 mutant and wild type were exposed to hydroxyurea (HU) or methyl methanesulfonate (MMS)， induction of RNR3 were observed. The b-galactosidase activity is 8.27?.38 or 9.55?0.24 fold to basal levels in WEB2 mutant， but is far lower than in wild type， which are 83.32?.42 or 124.67?.87 ford. RAD53 mutant has lower induction of RNR3， 2.37?.18 and 2.91?.13 fold， respectively. The results suggest that WEB2 gene mutation blocks the checkpoint signal transduction to RNR3 gene. WEB2 gene acts upstream of RNR3 gene， less important than RAD53， may function together with other genes in regulation of RNR3 expression.
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