Girdin: an essential component of pre-replicative complex in human cells

A central event in the initiation of DNA replication in eukaryotes is the assembly of pre-replicative complex (pre-RC) on specific chromatin sites known as DNA replication origins. The pre-RC assembly process differs between budding and fission yeasts. In fission yeast, Sap1 directly participates in pre-RC assembly, together with the four initiation factors: ORC, Cdc18/Cdc6, Cdt1, and MCM. In metazoans, the nature of DNA replication origins is not defined and the mechanism of pre-RC assembly remains incompletely known. In this study, Girdin was identified as an essential replication initiation factor in human cells. Similar to the activity of Sap1, human Girdin binds to DNA origins, interacts with ORC, and is required for pre-RC assembly due to its essential role in recruitment of Cdc6 to DNA origins. Thus, DNA origins in human or metazoans are defined as including two elements, one bound by ORC and the other bound by Girdin.