Franck J P, Wright J M
Department of Biology, Dalhousie University, Halifax, N.S., Canada.
Genome. 1993 Feb;36(1):187-94. doi: 10.1139/g93-025.
We have cloned and sequenced a 1900-bp EcoRI fragment (SATB) from the tilapiine fish Oreochromis niloticus. The SATB sequence is highly reiterated in the tilapiine genome and organized in long tandem arrays. A 760-bp HindIII fragment, an internal component of SATB, has also been cloned and sequenced from the related tilapiine species Oreochromis hornorum. Hybridization of the radiolabelled 760-bp HindIII repeat detected the presence of the SATB repeat in the genomes of several tilapiine species as well as the haplochromine species Haplochromis (Protomelas) similis. The 760-bp HindIII fragment did not hybridize to genomic DNA of Etroplus maculatus (an Asian cichlid) or to that of Cichlasoma meeki (a South American cichlid). The SATB repeat sequence is 56% AT and constitutes 0.2-5% of the tilapiine genome depending on the species examined. Four imperfect 21-bp direct repeat sequences are present within the cloned 1900-bp EcoRI repeat. Alignment of the four direct repeats from the O. niloticus cloned 1900-bp DNA and the two homologous direct repeats from the O. hornorum 760-bp HindIII repeat revealed a core motif of 11 bp that exhibits 100% sequence identity between all of the direct repeats. The conservation of this motif in the SATB repeat suggests that this sequence may be under selective constraint.
我们从罗非鱼尼罗罗非鱼中克隆并测序了一个1900 bp的EcoRI片段（SATB）。SATB序列在罗非鱼基因组中高度重复，并以长串联阵列形式组织。一个760 bp的HindIII片段，即SATB的内部组成部分，也已从相关的罗非鱼物种霍氏罗非鱼中克隆并测序。用放射性标记的760 bp HindIII重复序列进行杂交，检测到几种罗非鱼物种以及单倍体丽鱼科物种似原黑丽鱼的基因组中存在SATB重复序列。760 bp HindIII片段与黄斑埃氏鱼（一种亚洲丽鱼科鱼）或米氏丽体鱼（一种南美丽鱼科鱼） 的基因组DNA不杂交。SATB重复序列的AT含量为56%，根据所检测的物种不同，占罗非鱼基因组的0.2%-5%。在克隆的1900 bp EcoRI重复序列中存在四个不完美的21 bp直接重复序列。尼罗罗非鱼克隆的1900 bp DNA中的四个直接重复序列与霍氏罗非鱼760 bp HindIII重复序列中的两个同源直接重复序列的比对显示，有一个1l bp的核心基序，在所有直接重复序列之间表现出100%的序列同一性。SATB重复序列中该基序的保守性表明该序列可能受到选择限制。
