Vol. 168, No. 6, March 14, 2005. Page 849.

In the news story “Decondensation at the fork” (http://www.jcb.org/cgi/content/full/168/6/849-b) about the involvment of histone HI in decondensation at the replication fork, it was stated that “Cdk2 is required for S-phase progression” and “Cdc45 induces phosphorylation of histone H1 by recruiting Cdk2, a protein required for entry into S phase as well as progression through it.” It has been pointed out to us that Cdk2 is not absolutely essential for cell cycle progression, as knockout mice are viable (Berthet et al., 2003. Curr. Biol. 13:1775–1785), and Cdk2 is essential for meiosis but not mitosis (Ortega et al., 2003. Nat. Genet. 35:25–31).