title: Protein kinase B/Akt may regulate G2/M transition in the fertilized mouse egg by changing the localization of p21(Cip1/WAF1).
abstract: Protein kinase B (PKB, also called Akt) is known as a serine/threonine protein kinase. Some studies indicate that the Akt signalling pathway strongly promotes G2/M transition in mammalian cell cycle progression, but the mechanism remains to be clarified, especially in the fertilized mouse egg. Here, we report that the expression of Akt at both the protein and mRNA level was highest in G2 phase, accompanied by a peak of Akt activity. In addition, the subcellular localization of p21(Cip1/WAF1) has been proposed to be critical in the cell cycle. Hence, we detected the expression and localization of p21(Cip1/WAF1) after injecting fertilized mouse eggs with Akt mRNA. In one-cell stage fertilized embryos microinjected with mRNA coding for a constitutively active myristoylated Akt (myr-Akt), p21(Cip1/WAF1) was retained in the cytoplasm. Microinjection of mRNA of kinase-deficient Akt(Akt-KD) resulted in nuclear localization of p21(Cip1/WAF1) . Meanwhile, microinjection of different types of Akt mRNA affected the phosphorylation status of p21(Cip1/WAF1) . However, there was no obvious difference in the protein expression of p21(Cip1/WAF1) . Therefore, Akt controls the cell cycle by changing the subcellular localization of p21(Cip1/WAF1) , most likely by affecting the phosphorylation status of p21(Cip1/WAF1) .
authors.affiliation: Department of Biochemical and Molecular Biology, China Medical University, Shenyang, Liaoning, China.
authors.forename: Di-Di
authors.initials: DD
authors.lastname: Wu
authors.forename: Chen
authors.initials: C
authors.lastname: Feng
authors.forename: Xiao-Yan
authors.initials: XY
authors.lastname: Xu
authors.forename: Jian-Ying
authors.initials: JY
authors.lastname: Xiao
authors.forename: Chao
authors.initials: C
authors.lastname: Liu
authors.forename: Jun
authors.initials: J
authors.lastname: Meng
authors.forename: En-Hua
authors.initials: EH
authors.lastname: Wang
authors.forename: Bing-Zhi
authors.initials: BZ
authors.lastname: Yu
mesh_terms: D000818:Animals; D002455:Cell Division; D002467:Cell Nucleus / Q000378:metabolism; D049109:Cell Proliferation; D050759:Cyclin-Dependent Kinase Inhibitor p21 / Q000378:metabolism*; D003593:Cytoplasm / Q000378:metabolism; D047108:Embryonic Development; D005260:Female; D005455:Fluorescent Antibody Technique; D016195:G2 Phase; D008297:Male; D051379:Mice; D008845:Microinjections; D009865:Oocytes / Q000166:cytology / Q000378:metabolism; D010766:Phosphorylation; D051057:Proto-Oncogene Proteins c-akt / Q000378:metabolism; D012333:RNA, Messenger / Q000378:metabolism; D015053:Zygote / Q000166:cytology* / Q000378:metabolism
chemical_list: C493957:Cdkn1a protein, mouse; D050759:Cyclin-Dependent Kinase Inhibitor p21; D012333:RNA, Messenger; C514862:Akt1 protein, mouse; D051057:Proto-Oncogene Proteins c-akt