PLK4 phosphorylation of CP110 is required for efficient centriole assembly

<p>Centrioles are assembled during S phase and segregated into 2 daughter cells at the end of mitosis. The initiation of centriole assembly is regulated by polo-like kinase 4 (PLK4), the major serine/threonine kinase in centrioles. Despite its importance in centriole duplication, only a few substrates have been identified, and the detailed mechanism of PLK4 has not been fully elucidated. CP110 is a coiled-coil protein that plays roles in centriolar length control and ciliogenesis in mammals. Here, we revealed that PLK4 specifically phosphorylates CP110 at the S98 position. The phospho-resistant CP110 mutant inhibited centriole assembly, whereas the phospho-mimetic CP110 mutant induced centriole assembly, even in PLK4-limited conditions. This finding implies that PLK4 phosphorylation of CP110 is an essential step for centriole assembly. The phospho-mimetic form of CP110 augmented the centrosomal SAS6 level. Based on these results, we propose that the phosphorylated CP110 may be involved in the stabilization of cartwheel SAS6 during centriole assembly.</p

Desmethyl Macrolides: Synthesis and Evaluation of 4,10-Didesmethyl Telithromycin

Novel sources of antibiotics are required to keep pace with the inevitable onset of bacterial resistance. Continuing with our macrolide desmethylation strategy as a source of new antibiotics, we report the total synthesis, molecular modeling, and biological evaluation of 4,10-didesmethyl telithromycin (<b>4</b>), a novel desmethyl analogue of the third-generation drug telithromycin (<b>2</b>). Telithromycin is an FDA-approved ketolide antibiotic derived from erythromycin (<b>1</b>). We found 4,10-didesmethyl telithromycin (<b>4</b>) to be four times more active than previously prepared 4,8,10-tridesmethyl congener (<b>3</b>) in MIC assays. While less potent than telithromycin (<b>2</b>), the inclusion of the C-8 methyl group has improved biological activity, suggesting that it plays an important role in antibiotic function

Desmethyl Macrolides: Synthesis and Evaluation of 4,10-Didesmethyl Telithromycin

Novel sources of antibiotics are required to keep pace with the inevitable onset of bacterial resistance. Continuing with our macrolide desmethylation strategy as a source of new antibiotics, we report the total synthesis, molecular modeling, and biological evaluation of 4,10-didesmethyl telithromycin (<b>4</b>), a novel desmethyl analogue of the third-generation drug telithromycin (<b>2</b>). Telithromycin is an FDA-approved ketolide antibiotic derived from erythromycin (<b>1</b>). We found 4,10-didesmethyl telithromycin (<b>4</b>) to be four times more active than previously prepared 4,8,10-tridesmethyl congener (<b>3</b>) in MIC assays. While less potent than telithromycin (<b>2</b>), the inclusion of the C-8 methyl group has improved biological activity, suggesting that it plays an important role in antibiotic function

Comparison of clinicopathological variables according to MHC-II expression in tumor cells.

<p>Comparison of clinicopathological variables according to MHC-II expression in tumor cells.</p

Multisite phosphorylation of C-Nap1 releases it from Cep135 to trigger centrosome disjunction

During mitotic entry, centrosomes separate to establish the bipolar spindle. Delays in centrosome separation can perturb chromosome segregation and promote genetic instability. However, interphase centrosomes are physically tethered by a proteinaceous linker composed of C-Nap1 (also known as CEP250) and the filamentous protein rootletin. Linker disassembly occurs at the onset of mitosis in a process known as centrosome disjunction and is triggered by the Nek2-dependent phosphorylation of C-Nap1. However, the mechanistic consequences of C-Nap1 phosphorylation are unknown. Here, we demonstrate that Nek2 phosphorylates multiple residues within the C-terminal domain of C-Nap1 and, collectively, these phosphorylation events lead to loss of oligomerization and centrosome association. Mutations in non-phosphorylatable residues that make the domain more acidic are sufficient to release C-Nap1 from the centrosome, suggesting that it is an increase in overall negative charge that is required for this process. Importantly, phosphorylation of C-Nap1 also perturbs interaction with the core centriolar protein, Cep135, and interaction of endogenous C-Nap1 and Cep135 proteins is specifically lost in mitosis. We therefore propose that multisite phosphorylation of C-Nap1 by Nek2 perturbs both oligomerization and Cep135 interaction, and this precipitates centrosome disjunction at the onset of mitosis

Desmethyl Macrolides: Synthesis and Evaluation of 4‑Desmethyl Telithromycin

Novel sources of antibiotics are needed to address the serious threat of bacterial resistance. Accordingly, we have launched a structure-based drug design program featuring a desmethylation strategy wherein methyl groups have been replaced with hydrogens. Herein we report the total synthesis, molecular modeling, and biological evaluation of 4-desmethyl telithromycin (<b>6</b>), a novel desmethyl analogue of the third-generation ketolide antibiotic telithromycin (<b>2</b>) and our final analogue in this series. While 4-desmethyl telithromycin (<b>6</b>) was found to be equipotent with telithromycin (<b>2</b>) against wild-type bacteria, it was 4-fold less potent against the A2058G mutant. These findings reveal that strategically replacing the C4-methyl group with hydrogen (i.e., desmethylation) did not address this mechanism of resistance. Throughout the desmethyl series, the sequential addition of methyls to the 14-membered macrolactone resulted in improved bioactivity. Molecular modeling methods indicate that changes in conformational flexibility dominate the increased biological activity; moreover, they reveal <b>6</b> adopts a different conformation once bound to the A2058G ribosome, thus impacting noncovalent interactions reflected in a lower MIC value. Finally, fluorescence polarization experiments of <b>6</b> with <i>E. coli</i> ribosomes confirmed <b>6</b> is indeed binding the ribosome