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Surrogate origins of replication in the mitochondrial genomes of ori‐zero petite mutants of yeast.
Author(s) -
Goursot R.,
Mangin M.,
Bernardi G.
Publication year - 1982
Publication title -
the embo journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 7.484
H-Index - 392
eISSN - 1460-2075
pISSN - 0261-4189
DOI - 10.1002/j.1460-2075.1982.tb01234.x
Subject(s) - biology , genome , mutant , genetics , replication (statistics) , yeast , mitochondrial dna , mutation , evolutionary biology , computational biology , gene , virology
We have investigated the mitochondrial genome of eight ori‐zero spontaneous petite mutants of Saccharomyces cerevisiae. The tandem repeat units of these genomes do not contain any of the seven canonical ori sequences of the wild‐type genome. Instead, they contain one, or more, ori‐S sequences. These 44‐nucleotide long surrogate origins of replication are a subset of GC clusters characterized by a potential secondary fold with two sequences ATAG and GGAG, inserted in AT spacers, two AT base pairs just following them, a GC stem (broken in the middle, and, in most cases also near the base, by non‐paired nucleotides), and a terminal loop. This structure is reminiscent of that of GC clusters A and B from canonical ori sequences and supports the view (Bernardi, 1982a) that the GC clusters of the mitochondrial genome arose, by an expansion process, from the canonical ori sequences. Like the latter, ori‐S sequences are present in both orientations, are located in intergenic regions, and can be used as excision sequences when tandemly oriented. Again as in the case of canonical ori sequences, the density of ori‐S sequences on the repeat units of petite genomes are correlated with the replication efficiency of the latter, as assessed by the outcome of crosses with wild‐type or petite tester strains.