PLK1-mediated phosphorylation cascade activates Mis18 complex to ensure centromere inheritance

Design, synthesis and evaluation of novel cycloalkylthiophene-based aminopyrimidine derivatives as potent PLK1 inhibitors

PLK1 plays a pivotal role in cell-cycle regulation and has been well-characterized as a promising target for cancer therapy. Here, we synthesized a series of fused-thiophene based aminopyrimidine derivatives, and discovered a novel and potent PLK1 inhibitor compound 7n with an IC50 value of 38.5 nM. Analogue 7n exhibited remarkable antiproliferative efficacy toward HepG2, Huh7, H1299, and A549 cells, and hasn't any noticeable cytotoxic activity on the non-tumoural cell line HEK-293. Further mechanism studies indicated 7n arrested the cell cycle at the G2/M phase and induced apoptosis in HepG2 cells with a concentration-dependent manner. Molecular docking presented that 7n could occupy well the ATP-binding site of PLK1 with a U-shaped conformation. Collectively, these results provide new insights into the further development of fused-thiophene based aminopyrimidines as PLK1 inhibitors.

Increased maize chromosome number by engineered chromosome fission

Activation of synthetic centromeres on chromosome 4 in maize leads to its breakage and formation of trisomic fragments called neochromosomes. A limitation of neochromosomes is their low and unpredictable transmission rates due to trisomy. Here, we report that selecting for dicentric recombinants through male crosses uncovers stabilized chromosome 4 fission events, which split it into 4a-4b complementary chromosome pairs, where 4a carries a native centromere and 4b carries a synthetic one. The cells rapidly stabilized chromosome ends by de novo telomere formation, and the new centromeres spread among genes without altering their expression. When both 4a and 4b chromosomes were made homozygous, they segregated through meiosis indistinguishably from wild type and gave rise to healthy plants with normal seed set, indicating that the synthetic centromere was fully functional. This work leverages synthetic centromeres to engineer chromosome fission, raising the diploid chromosome number of maize from 20 to 22.

Non-nucleosomal (CENP-A/H4)2 - DNA complexes as a possible platform for centromere organization

The centromere is a part of the chromosome that is essential for the even segregation of duplicated chromosomes during cell division. It is epigenetically defined by the presence of the histone H3 variant CENP-A. CENP-A associates specifically with a group of 16 proteins that form the centromere-associated network of proteins (CCAN). In mitosis, the kinetochore forms on the CCAN to connect the duplicated chromosomes to the microtubules protruding from the cell poles. Previous studies have shown that CENP-A replaces H3 in nucleosomes, and recently the structures of CENP-A-containing nucleosomes in complex with CCANs have been revealed, but they show only a limited interaction between CCANs and CENP-A. Here, we report the cryoEM structure of 2x(CENP-A/H4)2-di-tetramers assembled on DNA in the absence of H2A/H2B histone dimer and speculate how (CENP-A/H4)2-tetramers and -di-tetramers might serve as a platform for CCAN organization.

Transitions in development - an interview with Kara McKinley

Kara McKinley is an Assistant Professor of Stem Cell and Regenerative Biology at Harvard University and a Freeman Hrabowski Scholar of the Howard Hughes Medical Institute. Kara's group studies the uterus to understand the biology of menstruation, advancing both reproductive health and regenerative biology through rodent models. We spoke to Kara over Teams to learn more about her transition to becoming a group leader, her insights on navigating the competitive tenure-track market in biology and her dedication to promoting gender diversity within academia.

Role of protein kinase PLK1 in the epigenetic maintenance of centromeres

The centromere, a chromosome locus defined by the histone H3-like protein centromeric protein A (CENP-A), promotes assembly of the kinetochore to bind microtubules during cell division. Centromere maintenance requires CENP-A to be actively replenished by dedicated protein machinery in the early G1 phase of the cell cycle to compensate for its dilution after DNA replication. Cyclin-dependent kinases (CDKs) limit CENP-A deposition to once per cell cycle and function as negative regulators outside of early G1. Antithetically, Polo-like kinase 1 (PLK1) promotes CENP-A deposition in early G1, but the molecular details of this process are still unknown. We reveal here a phosphorylation network that recruits PLK1 to the deposition machinery to control a conformational switch required for licensing the CENP-A deposition reaction. Our findings clarify how PLK1 contributes to the epigenetic maintenance of centromeres.