Abundant larval transcript-1 and -2 genes from Brugia malayi:: diversity of genomic environments but conservation of 5′ promoter sequences functional in Caenorhabditis elegans
Abundant larval transcript-1 and -2 genes from Brugia malayi:: diversity of genomic environments but conservation of 5′ promoter sequences functional in Caenorhabditis elegans
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DOI：
10.1016/s0166-6851(02)00219-0
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发表时间：
2002-11-01
影响因子：
1.5
通讯作者：
Maizels, RM
中科院分区：
文献类型：
--
作者：
Gomez-Escobar, N;Gregory, WF;Maizels, RM
两个丰富的幼虫转录本（alt）基因的基因组组织从马来丝虫线虫已被定义。这些基因的产物在氨基酸序列上有78%的相同性，并且在蚊媒感染性幼虫中以阶段特异性的方式高度表达。ALT-1以两个几乎相同的拷贝存在，以类似于7.6kb的反向重复序列组织，占据基因组的总共16 kb。ALT-2是位于与ALT-1不同的基因座的单拷贝基因。两个alt-1基因（alt-1.1和-1.2）在编码序列和内含子序列上分别有99.7%和99.5%的相同性。alt-1和alt-2都含有3个内含子，alt-2的第三个内含子在实验室维持菌株的不同个体寄生虫中表现出明显的大小多态性。alt-1.1/1.2（分别为26和6 kb）和alt-2（分别为6和4 kb）上游和下游的基因组序列显示，两个基因都不在多重阵列中，也不是操纵子。最值得注意的是，alt-1和alt-2的相邻基因彼此之间没有相似性，或者与秀丽隐杆线虫中远距离alt同源物侧翼的基因没有相似性。尽管侧翼基因存在这种多样性，5' UTR区在每个B的上游延伸约800。马来人ALT基因显示出高度的相似性（总体上59%的同一性与77-86%的同一性的片段）。推测该区域可能含有保守的启动子元件，含有B的构建体。将具有或不具有编码序列的malayi alt 5' UTR与β-半乳糖苷酶报告蛋白融合。将这些构建体注射到C.对线虫和后代进行β-半乳糖表达染色。我们的研究结果表明，alt-1和alt-2结构在线虫的肠道细胞中的表达相对较强，从蠕虫开始，一直持续到成年。此外，当构建体除了S' UTR之外还含有alt-1编码和内含子序列的片段时，表达增强。我们的结论是，高水平的alt转录在丝虫L3 s是不是由于从一个多拷贝基因家族的表达，但到一组强大的启动子元件之间共享的两个alt基因。(C)2002 Elsevier Science B. V.保留所有权利。
The genomic organisation of two abundant larval transcript (alt) genes from the filarial nematode Brugia malayi has been defined. The products of these genes are 78% identical in amino acid sequence, and are highly expressed in a stage-specific manner by mosquito-borne infective larvae. alt-1 is present as two near-identical copies organised in an inverted repeat of similar to7.6 kb, occupying a total of 16 kb of the genome. alt-2 is a single-copy gene at a different locus to alt-1. The two alt-1 genes (alt-1.1 and -1.2) are 99.7% identical in coding sequence and 99.5% in intronic sequences. Both alt-1 and -2 contain 3 introns, and the third intron of alt-2 exhibits a size polymorphism evident in different individual parasites from the laboratory-maintained strain. Genomic sequence up and down-stream from alt-1.1/1.2 (26 and 6 kb, respectively) and alt-2 (6 and 4 kb, respectively) show that neither gene is in a multiple array or an operon. Most notably, the neighbouring genes of alt-1 and -2 show no similarity to each other, or to the genes flanking the distant alt homologue in Caenorhabditis elegans. Despite this diversity in flanking genes, the 5' UTR tracts extending some 800 by upstream of each B. malayi alt gene show a high degree of similarity (overall 59% identity with tracts of 77-86% identity). Surmising that this region may contain conserved promoter elements, constructs containing the B. malayi alt 5' UTR with or without coding sequence were made fused to beta-galactosidase reporter protein. These constructs were injected into the syncytical gonad of C. elegans and progeny stained for beta-gal expression. Our results show relatively strong expression in the gut cells of C elegans for both alt-1 and -2 constructs, commencing in larval worms and continuing into adulthood. Moreover, expression was enhanced when constructs contained segments of alt-1 coding and intronic sequence in addition to the S' UTR. We conclude that the high level of alt transcription in filarial L3s is not due to expression from a multi-copy gene family but to a set of strong promoter elements shared between the two alt genes. (C) 2002 Elsevier Science B.V. All rights reserved.