A unique unnatural base pair between a C analogue, pseudoisocytosine, and an A analogue, 6-methoxypurine, in replication |
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Authors: | Hirao Ichiro Kimoto Michiko Yamakage Shun-ichi Ishikawa Masahide Kikuchi Jun Yokoyama Shigeyuki |
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Institution: | Yokoyama CytoLogic Project, ERATO, JST and RIKEN Genomic Sciences Center, 2-1 Hirosawa, Wako-shi, 351-0198, Saitama, Japan. ihirao@postman.riken.go.jp |
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Abstract: | Pseudoisocytidine, a C-nucleoside analogue of cytosine, has two possible isomers of the H1- and H3-forms. Enzymatic incorporation experiments confirmed the existence of the two isomers in solution, and the 2'-deoxyribonucleoside triphosphate of pseudoisocytosine (PIC) was incorporated into DNA opposite both guanine and 6-methoxypurine (M) by the Klenow fragment of Escherichia coli DNA polymerase I. In addition to the PIC*M pairing in replication, M also functioned as an A analogue and T was efficiently incorporated opposite M. Thus, the PIC*M pair is regarded as a base pair between a C analogue and an A analogue, and can mediate the interconversion between the G*C and A*T base pairs. The combination of PIC and M could be used as a G*C<-->A*T transition mutagen. |
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