Synthesis and characterization of poly[d(G-z5C)]. B-Z transition and inhibition of DNA methylase.
Deoxy-5-azacytidine 5'-triphosphate was synthesized and used as a substrate for the enzymatic synthesis of the polynucleotide poly[d(G-z5C)]. Whereas the triphosphate decomposes in solution, the azacytosine analogue incorporated into DNA is stable under conditions preserving the double-helical structure. Poly[d(G-z5C)] undergoes the transition to the left-handed Z conformation at salt (NaCl and MgCl2) concentrations approximately 30% higher than those required for unsubstituted poly[d(G-C)]. However, the incorporation of azacytidine potentiates the formation at room temperature of the Z helix stabilized by the transition metal Mn2+; in the case of poly[d(G-C)], a heating step is required. The spectral properties of the two polymers in the B and Z forms are similar. Both left-handed forms are recognized by anti-Z DNA immunoglobulins, indicating that the DNAs bear common antigenic features. Poly[d(G-z5C)] is not a substrate for the DNA cytosine 5-methyltransferase from human placenta. It is a potent inhibitor of the enzyme when tested in a competitive binding assay. These results are compatible with a very strong, possibly covalent, mode of interaction between methyltransferases and DNA containing 5-azacytosine.
McIntosh
L P
LP
Zielinski
W S
WS
Kalisch
B W
BW
Pfeifer
G P
GP
Sprinzl
M
M
Drahovsky
D
D
van de Sande
J H
JH
Jovin
T M
TM
D001374:Azacitidine / Q000031:analogs & derivatives / Q000138:chemical synthesis; D003570:Cytidine Triphosphate / Q000031:analogs & derivatives / Q000138:chemical synthesis; D004248:DNA (Cytosine-5-)-Methyltransferases / Q000037:antagonists & inhibitors*; D005260:Female; D006801:Humans; D007202:Indicators and Reagents; D007700:Kinetics; D009690:Nucleic Acid Conformation; D010920:Placenta / Q000201:enzymology; D011089:Polydeoxyribonucleotides / Q000138:chemical synthesis* / Q000494:pharmacology; D011247:Pregnancy; D013056:Spectrophotometry, Ultraviolet
D007202:Indicators and Reagents; D011089:Polydeoxyribonucleotides; D003570:Cytidine Triphosphate; C038673:5-aza-2'-deoxycytidine-5'-triphosphate; C047553:poly(deoxyguanylic-5-azadeoxycytidylic acid); D004248:DNA (Cytosine-5-)-Methyltransferases; D001374:Azacitidine