Disease relevance of ccna1

• Functional clam cyclin A and B proteins have been produced using a baculovirus expression system [1].

High impact information on ccna1

• Immunoblots with an anti-cyclin A antibody reveal that cyclin A is undetectable in oocytes, appears within 15 min of fertilization, and is destroyed near the end of each meiosis and mitosis [2].
• The clam embryo protein cyclin A induces entry into M phase and the resumption of meiosis in Xenopus oocytes [2].
• These findings indicate that the rise in cyclin A plays a direct and natural role in driving cells into M phase [2].
• The cloned cDNA and derived amino acid sequences of one of these, cyclin A, are presented here [2].
• While the cyclin E/Cdk2 complex appears to have a role in the initiation of DNA replication, another Cdk kinase, possibly cyclin A/Cdk, may be involved in a later step controlling the switch from initiation to elongation [3].

Biological context of ccna1

• High levels of cyclin A cause marked hyperactivation of cdc2 kinase and a stable arrest at the metaphase point in the cell cycle [1].
• Binding to cyclin A and phosphorylation of this threonine are both required to activate fully the histone H1 kinase activity of p33cdk2 [4].
• The post-MBT survival mechanism arrests cells in G(1) phase by increasing expression of the cyclin-dependent kinase inhibitor p27(Xic1). p27(Xic1) associates with cyclin D/Cdk4 and cyclin A/Cdk2 complexes to cause G(1)/S arrest, perhaps allowing more time for DNA repair [5].
• Together, these results strongly suggest that zygote-dependent deadenylation of cyclin A1 and cyclin B2 mRNAs is responsible for the downregulation of these proteins [6].
• This prevented histone B4 and cyclin A1 and B1 mRNA polyadenylation, indicating that the polyadenylation of these mRNAs is Mos dependent [7].

Anatomical context of ccna1

• This centriole separation activity is dependent on cyclin/cdk2 activity; depletion of either cdk2 or of the two activating cyclins, cyclin A and cyclin E, eliminates centriole separation activity [8].
• Cyclin A belongs to a family of proteins involved in the regulation of the eukaryotic cell cycle [9].
• Recombinant cyclin A bound to and activated cdc2 in a cell-free system, but cyclin A and cdk2 binding was not observed [9].
• The roles of cyclin A in the rapid activation of cyclin B-cdc2 kinase at meiosis I and II transition and in the maintenance of high maturation-promoting factor activity in mature unfertilized eggs are discussed [9].

Associations of ccna1 with chemical compounds

• Unlike the B-type cyclins, cyclin A is barely detectable in stage VI oocytes, and only starts to be made in significant amounts after oocytes are exposed to progesterone [10].
• In contrast, p34cdc2 is only weakly tyrosine phosphorylated when bound to cyclin A and activates rapidly [11].
• Analysis of embryos treated with hydroxyurea or cycloheximide showed widespread cellular apoptosis coincident with cyclin A cleavage [12].
• The increase in Mos protein and the activation of MAPK by injecting cyclin A protein into immature oocytes were both blocked also by cycloheximide treatment [13].

Analytical, diagnostic and therapeutic context of ccna1

• Reciprocal immunoprecipitations with anti-Xenopus Cdc2 or anti-Xenopus cyclin A1 antibodies specifically co-precipitate XOrc1 and XOrc2 [14].
• In Xenopus oocytes, mitogen-activated protein (MAP) kinase can be activated by progesterone treatment or by microinjection of cyclin A, both of which lead to activation of the cdc2 protein kinase [15].
• Cyclin A1 is a member of an A-type multigene family; however the cyclin A1 cDNA only recognizes a single band on northern blots [16].

References