The deamination of 5-methyl cytosine produces a mismatched base pair which of itself can not be distinguished from a mismatch arising from a different original base pair. We investigated whether the methylation remaining of the opposite strand in the symmetrical CpG dinucleotide might provide a signal for template choice in SV40. There is evidence that methylation may be a signal in procaryotes. / SV40 mismatched at the single Hpa II site (CCGG) was used to transfect CV-1 cells. The sequence at the Hpa II site in the resulting progeny was probed by restriction analysis. Methylation at the Hpa II site on the WT parental strand of the mismatch increased the frequency with which WT was observed in the progeny. This is interpreted as reflecting a preference for the methylated strand to be used as a template in mismatch repair. Methylation at the Hha I site, GCGC, 3 bases away from the mismatch did not increase the proportion of WT clones recovered when the methylation was present on the WT strand. However, when the WT strand of the mismatch was methylated by a bacterial host at the Eco RII, CC('A)GG, and the Mbo I, GATC, sites an increased preference for WT as template was observed. This effect was additive with the effect of Hpa II methylation. These effects were approximately equal even though Hpa II methylation involves only one site while Eco RII methylation and Mbo I methylation are present at 16 and 8 sites respectively. / Having a much stronger influence on strand choice than any methylation pattern was the position of nicks in the mismatch. When the heteroduplex was nicked at the unique Bam HI and Eco RI sites, 2187 bp and 1436 bp away from the mismatch respectively, the strand with the nick closest to the mismatch was preferentially used as the template. We demonstrate that this would not be expected if an enzyme recognizing the nick could move in only one direction. We suggest that this mismatch repair system may operate at the replication fork recognizing the transiently unmethylated nascent strand. / Source: Dissertation Abstracts International, Volume: 46-01, Section: B, page: 0064. / Thesis (Ph.D.)--The Florida State University, 1984.
| Identifer | oai:union.ndltd.org:fsu.edu/oai:fsu.digital.flvc.org:fsu_75503 |
| Contributors | HARE, JOAN TERESA., Florida State University |
| Source Sets | Florida State University |
| Detected Language | English |
| Type | Text |
| Format | 134 p. |
| Rights | On campus use only. |
| Relation | Dissertation Abstracts International |
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