Zakian, VA. “
Origin of replication from Xenopus laevis mitochondrial DNA promotes high-frequency transformation of yeast.”.
Proc Natl Acad Sci U S A 78.5 (1981): ,
78, 5, 3128-32. Print.
AbstractA specific fraction of chromosomal DNA from both yeast and a wide variety of other eukaryotes, but not from Escherichia coli, promotes high-frequency transformation in yeast. The plasmids containing these sequences are maintained as extra-chromosomal molecules in transformed cells. These results suggest that similar or identical sequences are used for the initiation of DNA replication in eukaryotes. To test this hypothesis, several foreign eukaryotic DNAs implicated directly or indirectly in the initiation of DNA replication have been examined for their ability to promote autonomous, extrachromosomal replication in yeast. Simian virus 40 DNA, amplified Xenopus laevis ribosomal DNA, X. laevis 5S ribosomal DNA, X. laevis mtDNA, and five different members of the Alu I family of human middle repetitive DNAs were cloned into the vector YIp5 and used to transform yeast. Of these DNAs, only Xenopus mtDNA promoted high-frequency transformation and extrachromosomal maintenance of YIp5 DNA. A 2.2-kilobase EcoRI fragment from the 17.4-kilobase mtDNA molecule was responsible for these activities. This fragment contains the sequence used for the initiation of replication in Xenopus mitochondria.
Zakian, VA, DW Wagner, and WL Fangman. “
Yeast L double-stranded ribonucleic acid is synthesized during the G1 phase but not the S phase of the cell cycle.”.
Mol Cell Biol 18 (1981): ,
1, 8, 673-9. Print.
AbstractThe cytoplasm of Saccharomyces cerevisiae contains two major classes of protein-encapsulated double-stranded ribonucleic acids (dsRNA's), L and M. Replication of L and M dsRNA's was examined in cells arrested in the G1 phase by either alpha-factor, a yeast mating pheromone, or the restrictive temperature for a cell cycle mutant (cdc7). [3H]uracil was added during the arrest periods to cells prelabeled with [14C]uracil, and replication was monitored by determining the ratio of 3H/14C for purified dsRNA's. Like mitochondrial deoxyribonucleic acid, both L and M dsRNA's were synthesized in the G1 arrested cells. The replication of L dsRNA was also examined during the S phase, using cells synchronized in two different ways. Cells containing the cdc7 mutation, treated sequentially with alpha-factor and then the restrictive temperature, enter a synchronous S phase when transferred to permissive temperature. When cells entered the S phase, synthesis of L dsRNA ceased, and little or no synthesis was detected throughout the S phase. Synthesis of L dsRNA was also observed in G1 phase cells isolated from asynchronous cultures by velocity centrifugation. Again, synthesis ceased when cells entered the S phase. These results indicate that L dsRNA replication is under cell cycle control. The control differs from that of mitochondrial deoxyribonucleic acid, which replicates in all phases of the cell cycle, and from that of 2-micron DNA, a multiple-copy plasmid whose replication is confined to the S phase.