Centromeric localization of αKNL2 and CENP-C proteins in plants depends on their centromere-targeting domain and DNA-binding regions

Abstract

In eukaryotes, accurate chromosome segregation during cell division relies on the centromeric histone H3 variant, CENH3. Our previous work identified KINETOCHORE NULL2 (αKNL2) as a plant CENH3 assembly factor, which contains a centromere-targeting motif, CENPC-k, analogous to the CENPC motif found in CENP-C. We also demonstrated that αKNL2 can bind DNA in vitro in a sequence-independent manner, without the involvement of its CENPC-k motif. In this study, we show that the CENPC-k and CENPC motifs alone are insufficient for centromere targeting in Nicotiana benthamiana and Arabidopsis thaliana. In silico analysis identified adjacent DNA-binding regions near the CENPC-k and CENPC motifs, suggesting their role in centromeric DNA interaction. We further demonstrated that protein fragments containing these motifs effectively target centromeres. Deletion of these DNA-binding domains reduced the centromeric localization of αKNL2-C, while fusing CENPC-k to the non-specific DNA-binding domain of histone-like nucleoid structuring protein from Escherichia coli successfully targeted it to centromeres. Our findings suggest that the centromeric targeting of αKNL2 and CENP-C proteins relies on the CENPC-k/CENPC motifs, and that their sequence-independent DNA-binding activity enhances their centromere anchoring. These insights into the mechanisms of αKNL2 and CENP-C targeting may facilitate the engineering of kinetochore structures by directing chromatin-modifying proteins to centromeres.