TOPBP1 Interacting Replication Stimulating Protein (Treslin)

Treslin is involved in the initiation of DNA replication. Treslin associated with replicating chromatin and interacted with a region of Topbp1 critical for DNA replication. Association of Treslin with Topbp1 was dependent on Cdk2, and Treslin was essential for loading of Cdc45 (CDC45L) onto replication origins. Knockdown of Treslin in U2OS cells by small interfering RNA resulted in a proliferative defect, with noticeable cell enlargement, accumulation of cells prior to entry into S phase, inhibited DNA replication, and absence of CDC45 binding to chromatin. Treslin-depleted U2OS cells did not undergo apoptosis, although apoptosis was extensive in Treslin-knockdown HeLa cells. U2OS cells depleted of Treslin accumulated phosphorylated H2AX (H2AFX), a marker of DNA damage, but showed no activation of the checkpoint kinase CHK1 (CHEK1).