Potential Z-DNA-forming elements in serum DNA from human systemic lupus erythematosus

DNA fragments were isolated from serum of a patient with systemic lupus erythematosus. The majority of the DNA was between 150 and 250 base pairs in length. The DNA was cloned into phage M13, and 10 recombinants were sequenced. The average GC content of the DNA was higher than total human DNA (43% against 38%), with some fragments as high as 63%. This DNA is rich in alternating purine-pyrimidine segments that are potentially Z-DNA-forming regions.