Pace T, Birago C, Janse C J, Picci L, Ponzi M
Laboratorio di Biologia Cellulare, Istituto Superiore di Sanità, Rome, Italy.
Mol Biochem Parasitol. 1998 Nov 30;97(1-2):45-53. doi: 10.1016/s0166-6851(98)00130-3.
The B7 gene of Plasmodium berghei, highly conserved within the genus Plasmodium, encodes a nuclear protein most likely involved in chromatin assembly. In this study we describe the transcription pattern of B7 during asexual multiplication and sexual differentiation of the parasites in the blood of the vertebrate host. Two alternative transcripts have been identified: one, 1.4 kb in length is specific for asexual blood stages; the other, 1.8 kb in length is specific for sexually differentiated cells (gametocytes). The processed mRNAs are identical in their coding region and differ only in their 5' untranslated regions (5' UTRs). We show here that the differences in 5' UTRs are the result of two mechanisms: (1) the use of alternative transcription initiation sites mapped at least 1.4 kb apart, which imply the existence of separate, stage-specific promoters; (2) the splicing of a 765 bp gametocyte-specific intron at the 5' UTR of the 1.8 kb transcript.
伯氏疟原虫的B7基因在疟原虫属内高度保守，编码一种很可能参与染色质组装的核蛋白。在本研究中，我们描述了该寄生虫在脊椎动物宿主血液中进行无性繁殖和有性分化期间B7的转录模式。已鉴定出两种可变转录本：一种长度为1.4 kb，是无性血液阶段所特有的；另一种长度为1.8 kb，是有性分化细胞（配子体）所特有的。加工后的mRNA在编码区相同，仅在其5'非翻译区（5' UTR）有所不同。我们在此表明，5' UTR的差异是由两种机制导致的：（1）使用了相距至少1.4 kb定位的可变转录起始位点，这意味着存在单独的、阶段特异性的启动子；（2）在1.8 kb转录本的5' UTR处对一个765 bp的配子体特异性内含子进行剪接。
