TY - JOUR
T1 - In Z-DNA the sequence G-C-G-C is neither methylated by Hha I methyltransferase nor cleaved by Hha I restriction endonuclease
AU - Vardimon, L.
AU - Rich, A.
PY - 1984
Y1 - 1984
N2 - Plasmids carrying 24- or 32-base-pair inserts of alternating (dG-dC) residues were used to analyze the level of methylation of the G-C-G-C sites by Hha I DNA methyltransferase and their cleavage by Hha I endonuclease in the B-DNA or Z-DNA conformation. In supercoiled plasmids in which the inserts formed Z-DNA, the extent of methylation at the insert G-C-G-C sites was dramatically lower than the level of methylation at the G-C-G-C sites located outside the insert in the same plasmid. Similarly, cleavage by Hha I endonuclease was sharply lowered when the insert was in the Z-DNA form. In the relaxed plasmid, all its G-C-G-C sites were methylated to the same extent and the unmethylated sites were readily cleaved. After treatment with the methylase, the super-coiled plasmid was linearized and then digested with Hha I restriction endonuclease. This exposed unmethylated G-C-G-C sites from the insert that had been protected against cleavage in the Z conformation. A chemical reaction was used to study the distribution of the unmethylated cytosine residues. No accumulation of unmethylated cytosine residues was found anywhere along the entire 32-base-pair insert, which is consistent with a cooperative B-Z transition.
AB - Plasmids carrying 24- or 32-base-pair inserts of alternating (dG-dC) residues were used to analyze the level of methylation of the G-C-G-C sites by Hha I DNA methyltransferase and their cleavage by Hha I endonuclease in the B-DNA or Z-DNA conformation. In supercoiled plasmids in which the inserts formed Z-DNA, the extent of methylation at the insert G-C-G-C sites was dramatically lower than the level of methylation at the G-C-G-C sites located outside the insert in the same plasmid. Similarly, cleavage by Hha I endonuclease was sharply lowered when the insert was in the Z-DNA form. In the relaxed plasmid, all its G-C-G-C sites were methylated to the same extent and the unmethylated sites were readily cleaved. After treatment with the methylase, the super-coiled plasmid was linearized and then digested with Hha I restriction endonuclease. This exposed unmethylated G-C-G-C sites from the insert that had been protected against cleavage in the Z conformation. A chemical reaction was used to study the distribution of the unmethylated cytosine residues. No accumulation of unmethylated cytosine residues was found anywhere along the entire 32-base-pair insert, which is consistent with a cooperative B-Z transition.
UR - http://www.scopus.com/inward/record.url?scp=0344054184&partnerID=8YFLogxK
U2 - 10.1073/pnas.81.11.3268
DO - 10.1073/pnas.81.11.3268
M3 - ???researchoutput.researchoutputtypes.contributiontojournal.article???
C2 - 6328508
AN - SCOPUS:0344054184
SN - 0027-8424
VL - 81
SP - 3268
EP - 3272
JO - Proceedings of the National Academy of Sciences of the United States of America
JF - Proceedings of the National Academy of Sciences of the United States of America
IS - 11 I
ER -