Cai J, DuBow M S
Department of Microbiology and Immunology, McGill University, Montréal, Canada.
Can J Microbiol. 1996 Jul;42(7):662-71. doi: 10.1139/m96-091.
A chromosomally located operon (ars) of Escherichia coli has been previously shown to be functional in arsenic detoxification. DNA sequencing revealed three open reading frames homologous to the arsR, arsB, and arsC open reading frames of plasmid-based arsenic resistance operons isolated from both E. coli and staphylococcal species. To examine the outline of transcriptional regulation of the chromosomal ars operon, several transcriptional fusions, using the luciferase-encoding luxAB genes of Vibrio harveyi, were constructed. Measurement of the expression of these gene fusions demonstrated that the operon was rapidly induced by sodium arsenite and negatively regulated by the trans-acting arsR gene product. Northern blotting and primer extension analyses revealed that the chromosomal ars operon is most likely transcribed as a single mRNA of approximately 2100 nucleotides in length and processed into two smaller mRNA products in a manner similar to that found in the E. coli R773 plasmid-borne ars operon. However, transcription was found to initiate at a position that is relatively further upstream of the initiation codon of the arsR coding sequence than that determined for the E. coli R773 plasmid's ars operon.
先前已证明大肠杆菌中一个位于染色体上的操纵子（ars）在砷解毒过程中发挥作用。DNA测序显示，有三个开放阅读框与从大肠杆菌和葡萄球菌物种中分离出的基于质粒的抗砷操纵子的arsR、arsB和arsC开放阅读框同源。为了研究染色体ars操纵子的转录调控概况，构建了几个使用哈氏弧菌编码荧光素酶的luxAB基因的转录融合体。对这些基因融合体表达的测量表明，该操纵子能被亚砷酸钠快速诱导，并受到反式作用的arsR基因产物的负调控。Northern印迹和引物延伸分析表明，染色体ars操纵子很可能转录为一条长度约为2100个核苷酸的单一mRNA，并以类似于在大肠杆菌R773质粒携带的ars操纵子中发现的方式加工成两个较小的mRNA产物。然而，发现转录起始于一个位置，该位置相对于arsR编码序列起始密码子的上游比大肠杆菌R773质粒的ars操纵子所确定的位置更远。
