Casein kinase TbCK1.2 regulates division of kinetoplast DNA, and movement of basal bodies in the African trypanosome
Fig 7
Kinetoplast division factor hypothesis.
In G1, trypanosomes have one basal body and a single kinetoplast. During S-phase, kDNA synthesis occurs and the probasal body migrates away from the mature basal body (Step 1 and 2). After separating by a distance >895 nm, the probasal body completes maturation (step 3) producing 1K1N trypanosomes with 2 mature basal bodies that are found near opposite ends of a kinetoplast containing uncleaved double-length kDNA [23]. We propose that presence of two basal bodies each at a pole of kinetoplast “licences” kDNA division. Subsequently, kinetoplast division factors (KDFs) are recruited close to, or into, the mitochondrion (Step 4). KDFs may recruit or activate a “kDNA cleavage/scission complex” to divide the kinetoplast (Step 5). In G2, separation of kinetoplasts is visible (Step 6), providing microscopic evidence of kDNA scission. Sorting of kinetoplasts into daughter trypanosomes occurs at cytokinesis (Step 7). Depiction of a “kDNA cleavage/scission complex” is hypothetical. Knockdown of TbCK1.2, or other KDFs, prevents scission of kDNA (see Fig 2). Molecular functions of other KDFs remain to be discovered. TAC-protein sub-complexes are projected to might mediate scission site selection and/or sorting of kinetoplasts (reviewed in [11]).