Biology subjects

Yuen, K. W. Y.

Publications and source records attributed to Yuen, K. W. Y..

2 recordsLinked to original sources

bioRxiv2020

RbAp46/48LIN-53 and HAT-1 are required for initial CENP-AHCP-3 deposition and de novo centromere formation in Caenorhabditis elegans embryos

Foreign DNA microinjected into the Caenorhabditis elegans germline forms episomal extra-chromosomal arrays, or artificial chromosomes (ACs), in embryos. Injected linear, short DNA fragments concatemerize into high molecular weight (HMW)-DNA arrays that are visible as punctate DAPI-stained foci in oocytes, which undergo chromatinization and centromerization in embryos. The inner centromere, inner and outer kinetochore components, including AIR-2, CENP-AHCP-3, Mis18BP1KNL-2 and BUB-1, assemble onto the nascent ACs during the first mitosis. Yet, due to incomplete DNA replication of the nascent ACs, centromeric proteins are not oriented at the poleward faces of the nascent ACs in mitosis, resulting in lagging ACs. The DNA replication efficiency of ACs improves over several cell cycles. We found that a condensin subunit, SMC-4, but not the replicative helicase component, MCM-2, facilitates de novo CENP-AHCP-3 deposition on nascent ACs. Furthermore, H3K9ac, H4K5ac, and H4K12ac are highly enriched on newly chromatinized ACs. HAT-1 and RbAp46/48LIN-53, which are essential for de novo centromere formation and segregation competency of nascent ACs, also hyperacetylate histone H3 and H4. Different from centromere maintenance on endogenous chromosomes, where Mis18BP1KNL-2 functions upstream of RbAp46/48LIN-53, RbAp46/48LIN-53 depletion causes the loss of both CENP-AHCP-3 and Mis18BP1KNL-2 initial deposition at de novo centromeres on ACs.

cell biology↗

bioRxiv2020

DNA Sequence Preference for De Novo Centromere Formation on a Caenorhabditis elegans Artificial Chromosome

Centromeric DNA sequences vary in different species, but share common characteristics, like high AT-content, repetitiveness, and low, but not no, transcriptional activity. Yet, neocentromeres can be found on non-centromeric, ectopic sequences, suggesting that centromeres can be established and maintained epigenetically. In contrast, canonical centromeric DNA sequences are more competent in de novo centromere formation on artificial chromosomes (ACs). To determine if specific DNA sequence features are preferred for new centromere formation, we injected different DNA sequences into the gonad of a holocentric model organism, Caenorhabditis elegans, to form ACs in embryos, and monitored mitotic AC segregation. We demonstrated that AT-rich sequences, but not repetitive sequences, accelerated de novo centromere formation on ACs. We also injected fragmented Saccharomyces cerevisiae genomic DNA to construct a less repetitive, more complex AC that can propagate through generations. By whole-genome sequencing and de novo assembly of AC sequences, we deduced that this AC was formed through non-homologous end joining. By CENP-AHCP-3 chromatin immunoprecipitation followed by sequencing (ChIP-seq), we found that CENP-AHCP-3 domain width on both the AC and endogenous chromosomes is positively correlated with AT-content. Besides, CENP-AHCP-3 binds to unexpressed gene loci or non-genic regions on the AC, consistent with the organization of endogenous holocentromeres.

cell biology↗