Bastos M C, Murphy E
Public Health Research Institute, New York, NY 10016.
EMBO J. 1988 Sep;7(9):2935-41. doi: 10.1002/j.1460-2075.1988.tb03152.x.
Tn554 is a high-frequency, site-specific, transposable element having integrative properties resembling those of lysogenic bacteriophages. Nucleotide sequence analysis indicates that Tn554 has three transposition genes, designated tnpA, tnpB and tnpC. Mutations in each of these were complemented efficiently in trans by clones containing internal fragments of Tn554; thus the products of these genes function in trans. Elements carrying deletions of the Tn554 termini could not be complemented. The product of tnpC is not absolutely required for transposition, since deletion mutations encompassing 80% of tnpC, as well as frameshift mutations located near the amino terminus of tnpC, transposed at frequencies as high as 2% of that observed with wild-type Tn554. However, such mutations affected the orientation of insertion. With wild-type Tn554 insertion occurs in a single orientation regardless of the orientation of the donor. In tnpC mutants insertion orientation was dictated by the orientation of Tn554 in the donor molecule. A mutant lacking the carboxy-terminal 59 residues of tnpB also exhibited altered insertion orientation. Thus it appears that the tnpC gene product is required for correct orientation of the element upon insertion and that this protein may interact with the carboxy-terminal portion of the tnpB gene product.
Tn554是一种高频、位点特异性的转座元件，其整合特性类似于溶原性噬菌体。核苷酸序列分析表明，Tn554有三个转座基因，分别命名为tnpA、tnpB和tnpC。这些基因中的每一个发生突变后，都能被含有Tn554内部片段的克隆有效地进行反式互补；因此，这些基因的产物具有反式功能。携带Tn554末端缺失的元件无法进行互补。转座并不绝对需要tnpC的产物，因为包含80%的tnpC的缺失突变以及位于tnpC氨基末端附近的移码突变，其转座频率高达野生型Tn554观察频率的2%。然而，这些突变影响了插入方向。对于野生型Tn554，无论供体的方向如何，插入都以单一方向发生。在tnpC突变体中，插入方向由供体分子中Tn554的方向决定。一个缺少tnpB羧基末端59个残基的突变体也表现出插入方向的改变。因此，似乎tnpC基因产物是元件插入时正确定向所必需的，并且该蛋白质可能与tnpB基因产物的羧基末端部分相互作用。
