Cyclin J protein (Cyclin J)

Cyclin J protein is a cyclin family member most closely related in sequence to A-type cyclins but lacks key structural motifs seen in classical mitotic cyclins; it defines a distinct cyclin subclass[1]. Cyclin J forms complexes with cyclin-dependent kinases (Cdk2 in Drosophila, Cdk1 in some systems) and regulates progression through S phase and mitosis during early embryonic development. In macrophages (mouse), Cyclin J acts via cell cycle–independent mechanisms to suppress activation and modulate immune function by promoting phosphorylation of transcriptional and metabolic regulators, reducing pro-inflammatory output[3]. Its gene is evolutionary conserved, and while dispensable for some aspects of fertility in Drosophila, it is required for robust cell division in the earliest embryonic stages[1][5]. Cyclin J-associated kinase activity has been experimentally inhibited by peptide aptamers and classic Cdk inhibitors, leading to cell cycle defects and altered chromosome segregation[1]. Cyclin J represents a molecular node integrating cell cycle and immune regulatory mechanisms, and may be a relevant therapeutic target for cancer and autoimmune diseases due to its control of cell proliferation and immune activation[3].

Other names

Cyclin JCdi5CCNJ (gene symbol in mammals)

Inhibition of Cyclin J/CDK complex blocks cell cycle progression; aptamers bind Cyclin J and prevent kinase activation. CDK inhibitors (such as Dacapo) block Cyclin J-associated kinase activity. Cyclin J–CDK complexes phosphorylate targets such as FoxK1 and Drp1, thereby modulating immune cell metabolism and activation.