cyclin L1 Background Information
Cell proliferation is controlled at specific stages of the cell cycle by distinct protein kinase complexes. These complexes consist of a catalytic subunit associating with a specific regulatory subunit to form the active kinase. The cyclins, which include cyclin A, B, C, D, E, F, G, H, I, K, L, T and their related proteins, including Dbf4, comprise the regulatory subunits of these kinase complexes. The controlled activation of the kinase complexes at various intervals of the cell cycle is regulated by the availability of the cyclins to the catalytic subunit. Unlike the catalytic subunit, which is expressed continually, the expression and stability of the regulatory subunit fluctuates depending on the stage of the cell cycle and, thereby, regulates the kinase activity. Cyclin L1 is a ubiquitously expressed nuclear protein that can be detected in higher levels in thymus. In neck and head squamous cell carcinomas, cyclin L1 can be overexpressed and is therefore often considered a proto-oncogene. It interacts with POLR2A, CDC2L and SFRS2. Cyclin L1 plays a role in the mRNA splicing process regulation.
