Yeast pre-meiotic DNA replication utilizes mitotic origin ARS1 independently of CDC7 function

In budding yeast, mitotic DNA replication initiates at sequence-specific replication origins, the prototype for which is ARS1. Initiation serves as the primary control point for mitotic DNA replication, and is catalyzed by the Cdc7 protein kinase. In contrast, premeiotic DNA replication apparently does not require Cdc7, and the existence and nature of specific replication origins in the meiotic division cycle have not been previously reported. We have begun to investigate the mechanism of premeiotic DNA synthesis by determining whether or not ARS1 functions as a DNA replication origin in meiosis. We have taken advantage of the fact that transcription through ARS1 disrupts its ability to function as an origin to show that ARS1 is required for premeiotic DNA replication of a plasmid bearing this element. Further, premeiotic replication from ARS1 still occurs in a cdc7 mutant strain held at conditions non-permissive for Cdc7 protein kinase activity. These findings reveal that premeiotic DNA replication can initiate from origins also used in mitosis, and is not regulated by Cdc7. Taken together with previous findings implicating Cdc7 in meiotic DNA recombination and induced mutagenesis, these findings prompt us to postulate that the Cdc7 protein kinase regulates some step common to several DNA metabolic processes such as local disassembly of chromatin or activation of a key component of the DNA metabolic machinery.