Lloyd R S, Augustine M L
Mutat Res. 1987 Aug;179(2):135-42. doi: 10.1016/0027-5107(87)90303-4.
The DNA sequences associated with a very high-frequency, spontaneous deletion event have been determined to be two 11-base direct repeats which also contain an internal 6-base palindrome. A parental M13 replicative form (RF) DNA harboring DNA fragments of the T4 denV gene contained these direct repeats and could only be maintained at 5% of the total RF DNA within an infected cell. The remaining RF DNA was deleted for all intervening sequences between the direct repeats (2.2-kb), but one copy of the direct repeat was retained after the deletion had occurred. This site-specific deletion was highly reproducible in that if parental-sized M13 RF DNA was gel purified and transformed back into cells, the deletion occurred at precisely the same sequence as before. Electron microscopic analyses of DNA extracted from cells transformed with parental-sized DNA revealed the presence of excised 2.2-kb double-stranded circular DNA molecules. This observation thus rules out a copy choice replication/deletion mechanism to account for this high-frequency deletion event.
与一个高频自发缺失事件相关的DNA序列已被确定为两个11碱基的直接重复序列，其中还包含一个内部6碱基的回文序列。携带T4 denV基因DNA片段的亲本M13复制型（RF）DNA包含这些直接重复序列，并且在感染细胞内只能以占总RF DNA 5%的比例维持。其余的RF DNA缺失了直接重复序列之间的所有间隔序列（2.2 kb），但在缺失发生后保留了一份直接重复序列。这种位点特异性缺失具有高度可重复性，即如果将亲本大小的M13 RF DNA进行凝胶纯化并重新转化回细胞中，缺失会在与之前完全相同的序列处发生。对用亲本大小的DNA转化的细胞中提取的DNA进行电子显微镜分析，发现存在切除的2.2 kb双链环状DNA分子。因此，这一观察结果排除了复制选择复制/缺失机制来解释这一高频缺失事件。
