The N-terminal Tail of C. elegans CENP-A Interacts with KNL-2 and is Essential for Centromeric Chromatin Assembly

de Groot, C.; Houston, J.; Davis, B.; Gerson-Gurwitz, A.; Monen, J.; Oegema, K.; Shiau, A. K.; Desai, A.

doi:10.1101/2020.12.28.424576

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bioRxiv · 10.1101/2020.12.28.424576

The N-terminal Tail of C. elegans CENP-A Interacts with KNL-2 and is Essential for Centromeric Chromatin Assembly

de Groot, C.·Houston, J.·Davis, B.·Gerson-Gurwitz, A.·Monen, J.·Oegema, K.·Shiau, A. K.·Desai, A.

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Abstract

Centromeres are epigenetically defined by the presence of the centromere-specific histone H3 variant CENP-A. A specialized loading machinery, including the histone chaperone HJURP/Scm3, participates in CENP-A nucleosome assembly. However, Scm3/HJURP is missing from multiple lineages, including nematodes, which rely on a CENP-A-dependent centromere. Here, we show that the extended N-terminal tail of C. elegans CENP-A contains a predicted structured region that is essential for centromeric chromatin assembly. Removal of this region of the CENP-A N-Tail prevents loading, resulting in failure of kinetochore assembly and defective chromosome condensation. By contrast, the N-Tail mutant CENP-A localizes normally in the presence of endogenous CENP-A. The portion of the N-Tail containing the predicted structured region binds to KNL-2, a conserved SANTA and Myb domain-containing protein (referred to as M18BP1 in vertebrates), that is specifically involved in CENP-A chromatin assembly. This direct interaction is conserved in the related nematode C. briggsae, despite divergence of the N-Tail and KNL-2 primary sequences. Thus, the extended N-Tail of CENP-A is essential for CENP-A chromatin assembly in C. elegans and partially substitutes for the function of Scm3/HJURP, in that it mediates an interaction of the specialized histone fold of CENP-A with KNL-2. These results highlight an evolutionary variation on centromeric chromatin assembly in the absence of a dedicated CENP-A-specific chaperone/targeting factor of the Scm3/HJURP family.

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de Groot, C., Houston, J., Davis, B., Gerson-Gurwitz, A., Monen, J., Oegema, K., Shiau, A. K., Desai, A.. 2020-12-28. The N-terminal Tail of C. elegans CENP-A Interacts with KNL-2 and is Essential for Centromeric Chromatin Assembly. https://doi.org/10.1101/2020.12.28.424576

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