Malaysian Applied Biology Journal

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Malays. Appl. Biol. (2008) 37(1): 1–9


WONG, C.M.V.L.,1* LEE, C.M.2 and RADU, S.3

1 Biotechnology Research Institute, Universti Malaysia Sabah, 88999 Kota Kinabalu, Sabah.
2 Institute of Bioscience, 3 Department of Food Science, Faculty of Food Science and Technology,
Universiti Putra Malaysia, 43400 Serdang, Selangor
*E-mail: This e-mail address is being protected from spambots. You need JavaScript enabled to view it


The stable maintenance of the 2? plasmid depends on its ability to overcome the maternal inheritance bias, which in S. cerevisiae normally results in failure to transmit the plasmid to daughter cells. In addition to the plasmid-encoded proteins Rep1p and Rep2p acting on the plasmid DNA locus STB, it has been shown that other chromosome-encoded yeast proteins are required. We have previously shown that chromosome-encoded chromatin remodeling protein, Rsc2p was essential for the stability of the 2? plasmid. Recently several chromosome-encoded chromatin remodelling genes CST6, SBA1 and NAT1 have been found to affect the stability of chromosomes. These genes may also be important for the maintenance of the 2? plasmid. Hence, this study was carried out to determine if CST6, SBA1 and NAT1 are required for the stability of the 2? plasmid. It was found that an overexpression of CST6, SBA1 or NAT1 did not affect the stability of 2? plasmid. Interestingly, disruption of NAT1 was found to affect the stability of 2? plasmid. Disruptions of CST6 and SBA1 affected the maintenance of the centromeric plasmid but not the 2? plasmid. Additionally, yeast mutagenesis produced three stable mutants, m1, m2 and m3 that lost the 2? plasmid rapidly. The phenotype of mutant m3 was rescued by the wildtype RSC2 gene, while mutant m1 was rescued by the wildtype NAT1 gene, confirming the results that the two genes were essential for the maintenance of the 2? plasmid. Another mutant, m2 was not rescued by the presence of either RSC2 or NAT1 indicating that there is at least another unidentified chromosomal gene that is required for the maintenance of the 2? plasmid.

Key words: 2? plasmid maintenance, stability, gene disruption


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