Kahmann R, Seiler A, Wulczyn F G, Pfaff E
Gene. 1985;39(1):61-70. doi: 10.1016/0378-1119(85)90108-8.
The mom gene of bacteriophage Mu encodes a DNA modification function which converts adenine to acetamido adenine in a sequence-specific manner. The mom gene itself is subject to a complex regulation: gene expression requires methylation by the Escherichia coli Dam methylase of specific sites upstream of the mom promoter and transactivation of the promoter by a Mu gene product. The requirement for transactivation can be overcome when mom is transcribed from foreign promoters. When cloned into various sites in pBR322, the mom gene is always found in an orientation where transcription from vector promoters is excluded. The productive orientation is lethal to the cell. This effect is mediated by the concerted action of the mom gene product and the product of gene com (control of mom, previously termed ORF-x) whose coding region overlaps the 5-coding region of the mom gene. When mom is expressed from its own promoter, internal deletions in com completely abolish expression of the mom gene. Fragments lacking the 5' end of com can be cloned downstream of constitutive plasmid promoters. The com gene product itself is not lethal to the cell. The region encoding mom has been cloned in pL expression vectors. The mom gene product, a peptide of 27 kDal, has been visualized on gels. Efficient expression of Mom from pL requires gene com. A fusion between MS-2 polymerase and com has been generated. The fusion product is made in large amounts, whereas the mom gene product is not overproduced although the gene is present on the same transcriptional unit.(ABSTRACT TRUNCATED AT 250 WORDS)
噬菌体Mu的mom基因编码一种DNA修饰功能，该功能能以序列特异性方式将腺嘌呤转化为乙酰氨基腺嘌呤。mom基因本身受到复杂的调控：基因表达需要大肠杆菌Dam甲基化酶对mom启动子上游的特定位点进行甲基化，以及Mu基因产物对启动子的反式激活。当mom从外源启动子转录时，反式激活的需求可以被克服。当克隆到pBR322的不同位点时，mom基因总是以排除载体启动子转录的方向存在。这种有效方向对细胞是致死的。这种效应是由mom基因产物和com基因（mom的控制基因，以前称为ORF-x）的产物协同作用介导的，其编码区域与mom基因的5'编码区域重叠。当mom从其自身启动子表达时，com内部缺失会完全消除mom基因的表达。缺乏com 5'端的片段可以克隆到组成型质粒启动子的下游。com基因产物本身对细胞不具有致死性。编码mom的区域已被克隆到pL表达载体中。mom基因产物是一种27kDal的肽，已在凝胶上显现出来。从pL高效表达Mom需要com基因。已经构建了MS-2聚合酶与com的融合体。融合产物大量产生，而mom基因产物尽管基因存在于同一转录单元上，但并未过量产生。（摘要截短至250字）
