title: Polypurine-polypyrimidine sequences adopt unwound structure in pBR322 form V DNA as probed by single-hit analysis of HpaII sites.
abstract: Structure at the polypurine-polypyrimidine sequences flanking the HpaII sites (CCGG) in pBR322 form V DNA was probed employing single-hit analysis using HpaII restriction endonuclease. Reduced cleavage efficiency of HpaII sites flanked by polypurine-polypyrimidine sequences suggested that under high torsional stress these sequences adopt unwound structures rendering these sites insensitive to restriction enzyme cleavage. In addition to polypurine-polypyrimidine sequences. HpaII sites flanked by alternating purine-pyrimidine sequence, a potential motif of left handed Z-DNA, were also found to be resistant to HpaII cleavage. Results obtained from various studies implicating structure sensitivity of restriction endonucleases and methylases were compiled and a direct correlation was observed between the occurrence of altered sites in a domain and its G/C content in pBR322 form V DNA.
authors.affiliation: Molecular Biophysics Unit, Indian Institute of Science, Bangalore.
authors.forename: R
authors.initials: R
authors.lastname: Bagga
authors.forename: S K
authors.initials: SK
authors.lastname: Brahmachari
mesh_terms: D001483:Base Sequence; D015342:DNA Probes; D004262:DNA Restriction Enzymes / Q000737:chemistry; D004269:DNA, Bacterial / Q000737:chemistry*; D019003:Deoxyribonuclease HpaII; D015252:Deoxyribonucleases, Type II Site-Specific; D008969:Molecular Sequence Data; D009690:Nucleic Acid Conformation; D010957:Plasmids; D011687:Purines / Q000737:chemistry*; D011743:Pyrimidines / Q000737:chemistry*
chemical_list: D015342:DNA Probes; D004269:DNA, Bacterial; D011687:Purines; D011743:Pyrimidines; D004262:DNA Restriction Enzymes; D019003:Deoxyribonuclease HpaII; D015252:Deoxyribonucleases, Type II Site-Specific; C030986:pyrimidine