Cyclin B3, G2/mitotic-specific (IPR015452)

Short name: Cyclin_B3

Overlapping homologous superfamilies


Family relationships

  • Cyclin (IPR039361)
    • Cyclin B3, G2/mitotic-specific (IPR015452)


Cyclins are eukaryotic proteins that play an active role in controlling nuclear cell division cycles [PMID: 12910258], and regulate cyclin dependent kinases (CDKs). Cyclins, together with the p34 (cdc2) or cdk2 kinases, form the Maturation Promoting Factor (MPF). There are two main groups of cyclins, G1/S cyclins, which are essential for the control of the cell cycle at the G1/S (start) transition, and G2/M cyclins, which are essential for the control of the cell cycle at the G2/M (mitosis) transition. G2/M cyclins accumulate steadily during G2 and are abruptly destroyed as cells exit from mitosis (at the end of the M-phase). In most species, there are multiple forms of G1 and G2 cyclins. For example, in vertebrates, there are two G2 cyclins, A and B, and at least three G1 cyclins, C, D, and E.

Cyclin homologues have been found in various viruses, including Saimiriine herpesvirus 2 (Herpesvirus saimiri) and Human herpesvirus 8 (HHV-8) (Kaposi's sarcoma-associated herpesvirus). These viral homologues differ from their cellular counterparts in that the viral proteins have gained new functions and eliminated others to harness the cell and benefit the virus [PMID: 11056549].

Cyclin B3 is conserved from Caenorhabditis elegans to Homo sapiens (Human) and has an undefined meiotic function in female, but not male Drosophila melanogaster (Fruit fly). Cyclin B3 interacts with cdk2, is localised to the nucleus, and is degraded during anaphase entry after the degradation of cyclin B1. Degradation is dependent on sequences conserved in a destruction box motif. Over expression of nondegradable cyclin B3 blocks the mitotic cell cycle in late anaphase, and at higher doses it can interfere with progression through G(1) and entry into S phase. The expression pattern of mammalian cyclin B3 suggests that it may be important for events occurring in early meiotic prophase I [PMID: 12185076].

In vertebrates, cyclins B1 and B2 function during M phase, whereas cyclin A is required for S phase as well as the G2 to M phase transition. The assignment of cyclin B3 to the B-type subfamily is based on cDNA-derived sequence and its pattern of expression in synchronised cells, both suggesting a distant relationship to other B-type cyclins. Interestingly, however, cyclin B3 also displays properties that resemble those of A- rather than B-type cyclins [PMID: 8313904].

GO terms

Biological Process

GO:0010389 regulation of G2/M transition of mitotic cell cycle
GO:0000079 regulation of cyclin-dependent protein serine/threonine kinase activity

Molecular Function

GO:0019901 protein kinase binding

Cellular Component

No terms assigned in this category.

Contributing signatures

Signatures from InterPro member databases are used to construct an entry.