OrcCdc6

OrcCdc6 is a protein involved in the regulation of DNA replication in eukaryotic cells. It is a homolog of the bacterial Cdc6 protein and plays a crucial role in the formation of the pre-replication complex (pre-RC), which is essential for the initiation of DNA replication during the cell cycle.

OrcCdc6 functions by cooperating with other origin recognition complex (ORC) components to mark origins of replication. During the late mitotic and early G1 phases, OrcCdc6 binds to ORC at replication origins, facilitating the recruitment of the minichromosome maintenance (MCM) complex, which acts as the replicative helicase. This assembly commits the origin to replication in the upcoming S phase. Once the initiation process begins, OrcCdc6 is typically phosphorylated and degraded or exported from the nucleus to prevent re-replication.

Structurally, OrcCdc6 contains AAA+ ATPase domains, which are vital for its activity in origin licensing. These domains enable binding and hydrolysis of ATP, providing the energy necessary for conformational changes during pre-RC assembly.

The regulation of OrcCdc6 is tightly controlled by cell cycle-dependent mechanisms, including phosphorylation by cyclin-dependent kinases (CDKs) and interaction with other cell cycle regulators. Aberrations in OrcCdc6 function or expression levels have been linked to genomic instability and may contribute to tumorigenesis.

In summary, OrcCdc6 is a key licensing factor in DNA replication, ensuring the accurate and origin-specific duplication of the genome in eukaryotic cells.