Love J D, Liarakos C D, Moses R E
Biochemistry. 1981 Sep 1;20(18):5331-6. doi: 10.1021/bi00521a037.
The covalently closed circular duplex deoxyribonucleic acid (DNA) of phi X174 underwent progressive conversion to nicked and linear DNA with increasing bleomycin/phi X174 RFI DNA molecule ratios. The formation of linear DNA (a double-strand break) occurred under limited reaction conditions as low as an average of 0.2 single-strand break/phi X174 RFI DNA molecule. As bleomycin-produced linear DNA was further fragmented by bleomycin, a broad distribution of DNA fragments without notable concentrations of unique size was formed. Restriction enzymes PstI and SstII did not generate discrete fragments from bleomycin-produced full-length linear phi X174 DNA, nor did bleomycin cleavage generate discrete fragments from HpaII or PstI digests of phi X174 RFI. These findings suggest that bleomycin does not act at a few specific sites on phi X174 RFI DNA. The single-strand nick appeared to be the preferred site for bleomycin action for a second cleavage in a phi X174 molecule.
随着博来霉素与φX174 RFI DNA分子比例的增加，φX174的共价闭合环状双链脱氧核糖核酸（DNA）逐渐转化为带切口的DNA和线性DNA。线性DNA（双链断裂）在有限的反应条件下即可形成，低至平均每φX174 RFI DNA分子0.2个单链断裂。由于博来霉素产生的线性DNA会被博来霉素进一步切割成片段，从而形成了广泛分布的DNA片段，没有明显浓度的特定大小片段。限制性内切酶PstI和SstII不能从博来霉素产生的全长线性φX174 DNA中产生离散片段，博来霉素切割也不能从φX174 RFI的HpaII或PstI消化产物中产生离散片段。这些发现表明，博来霉素并非作用于φX174 RFI DNA上的少数特定位点。单链切口似乎是博来霉素在φX174分子中进行第二次切割的优先作用位点。
