Interactions among rice ORC subunits.

The origin recognition complex (ORC) is composed of six subunits and plays an important role in DNA replication in all eukaryotes. The ORC subunits OsORC6 as well as the other five ORC subunits in rice were experimentally isolated and sequenced. It indicated that there also exist six ORC subunits in rice. Results of RT-PCR indicated that expression of all the rice ORC genes are no significant difference under 26°C and 34°C. Yeast two hybridization indicated that OsORC2, -3, -5 interact with each other. OsORC5 can then bind OsORC4 to form the OsORC2, -3,-4,-5 core complex. It suggested that the basic interactions have been conserved through evolution. No binding of OsORC1 and OsORC6 with the other subunits were observed. A model of ORC complex in rice is proposed.