Cyclin A2-CDK2 regulates embryonic gene activation in 1-cell mouse embryos

Dev Biol. 2005 Oct 1;286(1):102-13. doi: 10.1016/j.ydbio.2005.07.012.


Recruitment of maternal mRNA in mice appears essential for embryonic gene activation (EGA) that is initiated in the 1-cell stage. The identity of which recruited mRNAs is responsible, however, is not known. We report here that recruitment of cyclin A2 mRNA may be critical for EGA. Cyclin A2 protein accumulates in pronuclei between 6 and 12 h after fertilization, the time when EGA is initiated. This cyclin A2 may be generated from maternally recruited cyclin A2 mRNA because its accumulation was inhibited by 3'-deoxyadenosine, which inhibits mRNA polyadenylation. When CDK2 activity or pronuclear accumulation of cyclin A2 was inhibited with CDK2 inhibitors or by microinjected siRNAs, respectively, DNA replication was not inhibited but the increase of transcriptional activity was prevented. In addition, microinjection of recombinant cyclin A2-CDK2 protein increased transcriptional activity. Cyclin A2-CDK2 is activated following egg activation, because an increase in phosphorylation of retinoblastoma protein was observed using antibodies that recognize site-specific phosphorylation catalyzed by this kinase and treatment with a CDK2 inhibitor or microinjection with cyclin A2 siRNAs prevented the increase in retinoblastoma protein phosphorylation. These results suggest that recruitment of maternal cyclin A2 mRNA following egg activation is linked to EGA.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Animals
  • Base Sequence
  • Cleavage Stage, Ovum / cytology
  • Cleavage Stage, Ovum / drug effects
  • Cleavage Stage, Ovum / metabolism*
  • Cyclin A / antagonists & inhibitors
  • Cyclin A / genetics*
  • Cyclin A / metabolism*
  • Cyclin-Dependent Kinase 2 / antagonists & inhibitors
  • Cyclin-Dependent Kinase 2 / metabolism*
  • Cycloheximide / pharmacology
  • DNA, Complementary / genetics
  • Deoxyadenosines / pharmacology
  • Female
  • Gene Expression Regulation, Developmental / drug effects
  • In Vitro Techniques
  • Mice
  • Mice, Inbred ICR
  • Pregnancy
  • Protein Kinase Inhibitors / pharmacology
  • Purines / pharmacology
  • RNA, Messenger / genetics
  • RNA, Messenger / metabolism
  • RNA, Small Interfering / administration & dosage
  • RNA, Small Interfering / genetics
  • Roscovitine
  • Transcriptional Activation


  • Cyclin A
  • DNA, Complementary
  • Deoxyadenosines
  • Protein Kinase Inhibitors
  • Purines
  • RNA, Messenger
  • RNA, Small Interfering
  • Roscovitine
  • Cycloheximide
  • Cdk2 protein, mouse
  • Cyclin-Dependent Kinase 2
  • cordycepin