YEAST AND MAMMALIAN REPLICATION INTERMEDIATES MIGRATE SIMILARLY IN 2-DIMENSIONAL GELS

In the budding yeast, Saccharomyces cerevisiae, DNA replication initia tes at specific, discrete chromosomal locations. At each initiation si te, a single small replication bubble is generated, which subsequently expands at Y-like replication forks. We wanted to know whether other eukaryotic organisms utilize similar initiation mechanisms. For this p urpose, replication intermediates (RIs) from three different organisms (Schizosaccharomyces pombe, Chinese hamster and human) were mixed ind ividually with RIs from S. cerevisiae and then subjected to two-dimens ional (2D) gel electrophoresis under conditions known to resolve molec ules having different structures. All of the RIs detected by the hybri dization probes we used for each organism migrated nearly identically to specific RIs of similar size from S. cerevisiae, implying that the detected RIs from all the studied organisms have very similar structur es and may therefore employ the same basic initiation mechanism.