Study on the specificity of DNA base sequence required for the transposition immunity of the (gamma) (delta) sequence

一个含有的质粒<gamma><delta>不能通过转座获得另一个拷贝<gamma><delta>（转座免疫），我们以前发现末端的38 bp序列<delta>足以介导免疫。在本研究中。而<gamma>末端38 bp的免疫活性较弱（1/45）。然后<gamma>合成具有和不具有侧翼5-bp序列的末端38-bp序列，并克隆到质粒pUC 13的SmaI位点，以观察侧翼碱基序列对转座免疫效率的影响。当<gamma>末端38 bp与天然侧翼序列GTAA之一一起克隆时。代替人工SmaI位点序列TCCCC，免疫活性增加了7倍。这似乎表明，转座免疫所需的碱基序列的特异性更喜欢AT丰富的侧翼序列，而不是GT丰富的序列。至于第36位和第38位之间的碱基序列，用ATG取代达特使免疫力降低1/28。由于ATG序列与免疫力最强的AAG序列（末端序列）仅相差一个碱基<delta>，因此对37位碱基的特异性极高。

A plasmid containing <gamma><delta> cannot acquire another copy of <gamma> <delta>by transposition (transposition immunity).We previously found that the 38-bp sequence of the <delta> terminal is sufficient to mediate the immunity. In the present study. however, the <gamma>-terminal 38 bp was shown to have weaker (1/45) immunity activity than the other. The <gamma>-terminal 38-bp sequence was then synthesized with and without a flanking 5-bp sequence and cloned into the SmaI-site of the plasmid pUC13 in order to see the effect of the flanking base sequence on the efficiency of transposition immunity. When the<gamma>-terminal 38 bp was cloned together with one of the natural flanking sequences GTAA. in stead of the artificial SmaI-site sequence TCCCC, immunity activity increased by 7-fold. It seems to suggest that the specificity of base sequence required for transposition immunity prefers AT-rich flanking sequence to GT-rich one. As for the base sequence between 36th and 38th, the substitution of TAT with ATG reduced the immunity by 1/28. Since the sequence ATG differs only one base from the sequnce AAG (the <delta>-terminal suquence), which had the strongest immunity, the specificity fo the base 37 must be extremely high.