Hudson A D, Carpenter R, Coen E S
AFRC, Institute of Plant Science Research, John Innes Institute, Norwich, UK.
Plant Mol Biol. 1990 May;14(5):835-44. doi: 10.1007/BF00016516.
We describe two novel ways in which changes in gene expression in Antirrhinum majus may arise as a consequence of the Tam3 transposition mechanism. One involves excision of Tam3 from the nivea gene promoter and insertion of two new Tam3 copies 3.4 kb and 2.1 kb away, on either side of the excision site. One of the new insertions is in the nivea coding region and completely blocks production of an active gene product. This allele probably arose by a symmetrical double transposition, following chromosome replication. The second case involves a small deletion at one end of Tam3 in the pallida gene, flanked by a sequence typical of a Tam3 excision footprint. This suggests that the end of Tam3 was cleaved at an early step in an attempted transposition and re-ligated back to its original flanking sequence. The alteration restores some expression to the pallida gene, suggesting that the ends of the intact Tam3 element contain components which can actively inhibit gene expression. The implications of these findings for the mechanism of Tam3 transposition and for the effects of Tam3 on host gene expression are discussed.
我们描述了两种新的方式，在这两种方式中，金鱼草基因表达的变化可能是Tam3转座机制的结果。一种方式涉及Tam3从nivea基因启动子处切除，并在切除位点两侧3.4 kb和2.1 kb处插入两个新的Tam3拷贝。其中一个新插入片段位于nivea编码区域内，完全阻断了活性基因产物的产生。这个等位基因可能是在染色体复制后通过对称双转座产生的。第二种情况涉及pallida基因中Tam3一端的小缺失，其两侧是典型的Tam3切除足迹序列。这表明Tam3的末端在一次尝试转座的早期步骤中被切割，并重新连接回其原始侧翼序列。这种改变使pallida基因恢复了一些表达，表明完整的Tam3元件末端含有能够积极抑制基因表达的成分。讨论了这些发现对Tam3转座机制以及Tam3对宿主基因表达影响的意义。
