Characterization of Prt1, a gene encoding for one of the subunits of the translation initiation factor 3 (eIF3), from Nicotiana tabacum

Translation initiation Factors play essential functions in the regulation o f protein synthesis. Although many genes (cDNAs) encoding several eukaryoti c initiation factors (eIFs) have been isolated in plants, genes encoding di fferent subunits of the largest eIF, eIF3, are poorly studied. We describe here the characterization of a cDNA encoding the first plant homologue of P RT1, one of the eIF3 subunits, from Nicotiana tabacum. The tobacco Prt1 cDN A is 2518 bp long and contains an open reading frame encoding a protein of 719 amino acids which shares sequence homology of 31-41% identity and 53-64 % similarity with the yeast and human PRT1 proteins. Southers blot analysis showed that the Prt1 gene is present as a single copy in the tobacco genom e. Northern blot analysis revealed that Prt1 transcript accumulates most ab undantly in tissues with high mitotic activity in tobacco plants. In the sy nchronized tobacco BY2 cells. Prt1 showed a cell-cycle regulated expression pattern. Its transcript level was maximal at M phase. An increase by a fac tor of about two was found upon G2/M transition. This increase was abolishe d when the cell cycle was arrested by the treatment with DNA synthesis-inhi bitors. (C) 1999 Elsevier Science ireland Ltd. All rights reserved.