Belostotsky D A, Meagher R B
Department of Genetics, University of Georgia, Athens 30602-7223, USA.
Plant Cell. 1996 Aug;8(8):1261-75. doi: 10.1105/tpc.8.8.1261.
Poly(A) tails of eukaryotic mRNAs serve as targets for regulatory proteins affecting mRNA stability and translation. Differential mRNA polyadenylation and deadenylation during gametogenesis and early development are now widely recognized as mechanisms of translational regulation in animals, but they have not been observed in plants. Here, we report that the expression of the PAB5 gene encoding one of the poly(A) binding proteins (PABPs) in Arabidopsis is restricted to pollen and ovule development and early embryogenesis. Furthermore, PAB5 is capable of rescuing a PABP-deficient yeast strain by partially restoring both poly(A) shortening and translational initiation functions of PABP. However, PAB5 did not restore the linkage of deadenylation and decapping, thus demonstrating that this function of PABP is not essential for viability. Also, like endogenous PABP, PAB5 expressed in yeast demonstrated genetic interaction with a recently characterized yeast protein SIS1, which is also involved in translational initiation. We propose that PAB5 encodes a post-transcriptional regulatory factor acting through molecular mechanisms similar to those reported for yeast PABP. This factor may have evolved further to post-transcriptionally regulate plant sexual reproduction and early development.
真核生物信使核糖核酸（mRNA）的聚腺苷酸（Poly(A)）尾可作为影响mRNA稳定性和翻译的调控蛋白的作用靶点。配子发生和早期发育过程中mRNA的差异聚腺苷酸化和去腺苷酸化，如今已被广泛认为是动物体内翻译调控的机制，但在植物中尚未观察到此类现象。在此，我们报告称，拟南芥中编码一种聚腺苷酸结合蛋白（PABP）的PAB5基因的表达仅限于花粉和胚珠发育以及早期胚胎发生阶段。此外，PAB5能够通过部分恢复PABP的聚腺苷酸缩短和翻译起始功能，拯救一株缺乏PABP的酵母菌株。然而，PAB5并未恢复去腺苷酸化与脱帽作用之间的联系，因此表明PABP的这一功能对于细胞活力并非必不可少。同样，与内源性PABP一样，在酵母中表达的PAB5也与最近鉴定出的一种酵母蛋白SIS1存在遗传相互作用，SIS1也参与翻译起始过程。我们提出，PAB5编码一种转录后调控因子，其作用机制与已报道的酵母PABP类似。该因子可能已进一步进化，以便在转录后调控植物有性生殖和早期发育过程。
