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[[Image:CDC6_Function.jpg|thumb]] [[Image:Cdc6.png|thumb]] '''Cdc6''' is a [[protein]] that plays a crucial role in the initiation of [[DNA replication]] in [[eukaryotic cells]]. It is an essential component of the pre-replicative complex (pre-RC) that assembles at replication origins during the G1 phase of the [[cell cycle]] and is necessary for the formation of the replication fork during the S phase. Cdc6 functions alongside other key proteins, such as [[Origin Recognition Complex]] (ORC), [[Cdt1]], and [[MCM proteins]], to ensure that DNA replication is initiated accurately and only once per cell cycle.

== Function ==
Cdc6's primary role is to regulate the assembly of the pre-RC at replication origins. It acts after the ORC has bound to the DNA by recruiting Cdt1 and MCM helicase complexes, thereby completing the pre-RC. The MCM complex is crucial for unwinding the DNA helix, allowing replication machinery to access the single-stranded DNA. Cdc6, therefore, is pivotal in the transition from the G1 to the S phase of the cell cycle, ensuring that each segment of the genome is replicated once and only once.

== Regulation ==
The activity and stability of Cdc6 are tightly regulated by multiple mechanisms, including phosphorylation and proteolysis. Phosphorylation of Cdc6 by [[Cyclin-dependent kinases]] (Cdks) and [[Dbf4-dependent kinase]] (DDK) serves as a regulatory mechanism to prevent re-replication. Phosphorylated Cdc6 is either exported from the nucleus or targeted for degradation, ensuring that pre-RC assembly does not occur again within the same cell cycle.

== Clinical Significance ==
Alterations in Cdc6 expression or function have been implicated in the pathogenesis of various [[cancer]]s. Overexpression of Cdc6 can lead to uncontrolled cell proliferation due to deregulation of DNA replication, contributing to genomic instability, a hallmark of cancer cells. Therefore, Cdc6 is considered a potential target for cancer therapy, with research focused on developing inhibitors that can modulate its activity.

== Evolutionary Conservation ==
Cdc6 is evolutionarily conserved across eukaryotes, highlighting its fundamental role in DNA replication. Studies in model organisms, such as [[yeast]] and [[Xenopus laevis|Xenopus]], have contributed significantly to understanding Cdc6's function and regulation. These studies underscore the conserved mechanism of DNA replication initiation across different species.

== See Also ==
* [[Cell cycle]]
* [[DNA replication]]
* [[Origin Recognition Complex]]
* [[MCM proteins]]

[[Category:Cell biology]]
[[Category:Molecular biology]]
[[Category:Proteins]]

{{biology-stub}}

Cdc6 - Revision history

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