  It is well known that cyclins are a family of proteins that control
cell-cycle progression by activating cyclin-dependent kinase. Based on our
experimental results, we propose here a novel hypothesis that certain amplified
genomic-DNA fragments (AGFs) may also be required for the cell cycle
progression of eukaryotic cells and thus can be named as cell-cycle-associated
AGFs (CAGFs). Like fluctuation in cyclin levels during cell cycle progression,
these CAGFs are amplified and degraded at different points of the cell cycle.
The functions of CAGFs are unknown, but we speculate that CAGFs might be
involved in regulation of gene expression, genome protection, and formation of
certain macromolecular complexes required for the dynamic genome architecture
during cell cycle progression. Our experimental results also show that
chloroquine induces the production of CAGFs in Plasmodium falciparum,
suggesting that targeting cell cycle progression can be the primary mechanism
of chloroquine's antimalarial, anticancer, and immunomodulatory actions.
