The CCNL family includes two cyclins, CCNL1 and CCNL2. CCNL1 is involved in the regulation of RNA polymerase II (pol II) transcription. It functions in association with cyclin-dependent kinases (CDKs). CCNL2 is a novel RNA polymerase II-associated cyclin involved in pre-mRNA splicing. It may induce cell death, possibly by acting on the transcription and RNA processing of apoptosis-related factors. Members of this family contain two cyclin boxes. This model corresponds to the first one. The cyclin box is a protein binding domain.
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