Soto M, Requena J M, Alonso C
Centro de Biología Molecular Severo Ochoa (CSIC-UAM), Universidad Autónoma de Madrid, Spain.
Mol Biochem Parasitol. 1993 Oct;61(2):265-74. doi: 10.1016/0166-6851(93)90072-6.
Two tandemly linked genes are present in the Leishmania infantum genome that code for the acidic ribosomal PO protein. The genes are identical in the coding region, although a striking lack of nucleotide sequence conservation is observed when the boundaries of the coding regions between both genes are compared. The 3' untranslated regions of the two genes are, moreover, different in size. The deduced amino acid sequence of the L. infantum PO protein (LiPO) shows a high degree of sequence conservation, including the highly charged conserved C-terminal domain, with the ribosomal PO proteins of other eukaryotic organisms. Northern blot experiments showed that two different size class transcripts are expressed in the gene cluster and that the steady state level of each of the transcripts in logarithmic phase promastigotes is markedly different. The abundance of both transcripts is down-regulated in parasite cultures on reaching stationary phase. Since it seems that the two Leishmania ribosomal PO genes are expressed in a single polycistronic transcript, it is likely that the different levels of PO mRNAs observed in cultured cells is due to a postranscriptional regulatory mechanism.
婴儿利什曼原虫基因组中存在两个串联连接的基因，它们编码酸性核糖体PO蛋白。这两个基因在编码区是相同的，尽管在比较两个基因编码区的边界时，核苷酸序列的保守性明显缺乏。此外，这两个基因的3'非翻译区大小不同。婴儿利什曼原虫PO蛋白（LiPO）的推导氨基酸序列与其他真核生物的核糖体PO蛋白显示出高度的序列保守性，包括高度带电的保守C末端结构域。Northern印迹实验表明，在基因簇中表达了两种不同大小类别的转录本，并且在对数期前鞭毛体中每种转录本的稳态水平明显不同。在寄生虫培养物进入稳定期时，两种转录本的丰度均下调。由于似乎两个利什曼原虫核糖体PO基因在单个多顺反子转录本中表达，因此在培养细胞中观察到的不同水平的PO mRNA可能是由于转录后调控机制。
