Targeting of Arabidopsis KNL2 to Centromeres Depends on the Conserved CENPC-k Motif in Its C Terminus

Xenopus laevis M18BP1 Directly Binds Existing CENP-A Nucleosomes to Promote Centromeric Chromatin Assembly

“…We find that M18BP1 binds CENP-A nucleosomes via a conserved ‘CENP-C motif’ as suggested by recent bioinformatics and genetic analyses in zebrafish and Arabidopsis (Kral, 2015; Sandmann et al, 2017). M18BP1 chromatin recognition requires nucleosomes containing both the CENP-A Targeting Domain (CATD) and the CENP-A C-terminus (CAC), analogous to CENP-C. M18BP1 targeting to the centromere is negatively regulated during mitosis through post-translational modification of M18BP1.…”

“…We and others have observed that the M18BP1 CENP-C motif is conserved in insect, nematode, bird, reptile, frog, fish, and plant M18BP1 orthologues (Figure 2A) (Kral, 2015; Sandmann et al, 2017). With the exception of platypus ( O. anatinus ), the key nucleosome binding residues of the CENP-C motif are mutated in all mammalian orthologues we examined.…”

“…A recent bioinformatic analysis of CENP-C and M18BP1 identified a similar motif within M18BP1 proteins of fish, frogs and birds (Kral, 2015). Furthermore, a recent study identified a CENP-C motif-like sequence within Arabidopsis thaliana M18BP1/KNL2 that, when mutated, disrupts KNL2 targeting to centromeres (Sandmann et al, 2017). Alignment of diverse M18BP1 orthologues revealed conservation of a putative CENP-C motif within the Xenopus laevis M18BP1 nucleosome binding region (Figure 2A) consistent with the idea that M18BP1 may engage CENP-A nucleosomes via a CENP-C-like mechanism (Kral, 2015; Sandmann et al, 2017).…”

The Power of Xenopus Egg Extract for Reconstitution of Centromere and Kinetochore Function

“…However, M18BP1 localization and CENP-A assembly are only supported by chimeras containing both the CATD and the CAC (Westhorpe et al 2015). This suggests a CATD-binding protein like CENP-N—whose role has been implied in cell-based studies (Carroll et al 2009)—may be required, or that CENP-A assembly machinery itself recognizes CATD-containing chromatin (Sandmann et al 2017). As nascent CENP-A requires the CATD for HJURP-mediated incorporation into chromatin (Foltz et al 2009; Fachinetti et al 2013; Logsdon et al 2015), extract reconstitution provides an advantage over similar cell-based experiments that cannot distinguish such separate roles for the CATD in HJURP recognition and localization of the CENP-A assembly machinery.…”

A Tale of Two CENPCs: Centromere Localization of KINETOCHORE NULL2 and CENP-C

“…) mitotic chromosome segregation, reduced cenH3 gene expression, and less cenH3 protein at chromocenters of meristematic nuclei. In a new study, Sandmann et al (2017) provide further insight on the assembly and regulation of centromeric chromatin by examining KNL2 protein domains and nucleic acid binding. The authors conducted BLASTP searches and identified a CENPClike motif in Arabidopsis KNL2, designated CENPC-k; this domain is conserved in diverse eukaryotes, including many invertebrates and vertebrates, but is absent in some KNL2 homologs, such as those in therian mammals and Caenorhabditis elegans.…”