Fig. 4
From: CENP-A: the key player behind centromere identity, propagation, and kinetochore assembly
What is the first epigenetic mark of centromeres? Information provided by the literature brings the question of what is the first epigenetic mark of centromeres. Some evidence has shown that CENP-A nucleosome structure might be the feature for centromere identity. However, CENP-A incorporation and localization to centromeres are not passive cellular processes; therefore, CENP-A might not be the first epigenetic mark. Centromere identity could be through genetic features of DNA sequence (nucleic acid composition) or motif (CENP-B box, DNA methylation), but strong experimental evidence disputes this model. One marker that could link the two other hypotheses is KNL-2. This protein was shown to be essential for CENP-A localization to centromeres and genetically, it is the most upstream protein for this important cellular process. Thus, KNL-2 could be the first epigenetic mark of centromeres. For KNL-2 predicted structure: Orange is the SANTA domain and in purple is the Myb domain. (Published CENP-A nucleosome structure, Protein Data Bank reference # 3AN2 (Tachiwana et al. 2012); KNL-2 predicted structure (Zhang 2008))