The structure and transcription of an element interspersed between tandem arrays of mini-exon donor RNA genes in Trypanosoma brucei.
The structure and transcription of an element interspersed between tandem arrays of mini-exon donor RNA genes in Trypanosoma brucei.
复制标题
布氏锥虫微型外显子供体 RNA 基因串联阵列中散布的元件的结构和转录。
作者：
M. Carrington;I. Roditi;R. Williams
布氏锥虫的信使RNA在5‘端有相同的35个碱基。这35个碱基不是在基因组中连续编码的，而是从140个碱基的RNA(迷你外显子供体RNA)中捐赠出来的。微小外显子供体RNA(MedRNA)由1.35kbp的基因编码，以串联重复的形式出现。一个与微小外显子供体RNA MedRNA基因相关的DNA元件已经被鉴定，并通过限制性内切酶图谱和部分测序进行了表征。这个元件(MedRNA基因相关元件：MAE)的长度在5.5到7kbp之间变化。每个单倍体基因组中有20到40个拷贝的这种元素。在基因组DNA克隆中，MAE发生在两个MedRNA基因阵列之间和一个MedRNA基因阵列的两侧。在MedRNA基因上，MAE总是处于相同的方向。有人认为，在基因组中，MAE散布在MedRNA基因的串联阵列之间。对该元素的转录进行了研究。在稳态RNA中检测到来自MAE的一小部分70-80碱基的低水平转录本。核径流转录本研究表明，MAE在高水平转录，它们可能包含至少一个转录开始和停止。
Messenger RNAs in Trypanosoma brucei brucei have the same 35 bases at the 5' end. These 35 bases are not encoded contiguously in the genome, but are donated from a 140 base RNA (the mini-exon donor RNA). The mini-exon donor RNA (medRNA) is encoded by 1.35 kbp genes that occur in tandem repeats. A DNA element that is associated with mini-exon donor RNA medRNA genes has been identified and characterised by restriction enzyme mapping and partial sequencing. This element (the medRNA gene associated element: MAE) varies in length between 5.5 and 7 kbp. There are between 20 and 40 copies of the element per haploid genome. In clones of genomic DNA MAEs occurred between two medRNA gene arrays and on both sides of a medRNA gene array. The MAEs were always in the same orientation with respect to the medRNA genes. It is proposed that in the genome MAEs are interspersed between tandem arrays of medRNA genes. The transcription of the element has been investigated. Low levels of a 70-80 base transcript derived from a small part of MAE were detected in steady state RNA. Nuclear run off transcript studies indicated that MAEs were transcribed at high levels and that they possibly contain at least one start and stop of transcription.