Deoxyribonucleic-ribonucleic acid hybrid

Figure 7.5 Example of a chimeric oligonucleic acid and its modification. Chimeric RNA-DNA hybrids are used for correction of point mutations in target genes. One strand of this oligonucleic acid is composed of O-methyl-RNA (outline) with an interruption of 5 bases of deoxyribonucleic acid. X and Y are target residues for correction. In the complementary strand, there is a DNA nick, and T residues loop both ends. 3 -exonuclease and FEN-1 may act on the nick, PARP-1 possibly binds to and is activated by the nick, resulting in activation of damage response pathways. In the modified version, the 3 end is replaced by ribonucleic acids. The 5 end is extended, and the flipped back RNA tail is added. Thus, the nick is expected to be resistant to 3 -exonuclease and FEN-1. In addition, PARP-1 may not be activated by such a nick.

Diazines are aromatic six-membered heterocycles that contain two sp -hybrid-ized nitrogen atoms in the ring. The three diazine isomers are pyridazine (1,2-dia-zine), pyrimidine (1,3-diazine) and pyrazine (1,4-diazine). The most important naturally occurring diazines are the pyrimidine bases uracil, thymine, and cytosine, which comprise the fundamental nucleoside building blocks in deoxyribonucleic acid (DNA) and ribonucleic acid (RNA). Pyrazines occur frequently as... 

Berkower, I., Leis, J., and Hurwitz, J. (1973) Isolation and characterization of an endonuclease from Escherichia coli specific for ribonucleic acid in ribonucleic acid deoxyribonucleic acid hybrid structures J Biol C/iem. 248,5914-5921... 

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