A Dynamic Protein Interaction Landscape of the Human Centrosome-Cilium Interface.

The centrosome is the primary microtubule organizing center of the cells and templates the formation of cilia, thereby operating at a nexus of critical cellular functions. Here, we use proximity-dependent biotinylation (BioID) to map the centrosome-cilium interface; with 58 bait proteins we generate a protein topology network comprising >7,000 interactions. Analysis of interaction profiles coupled with high resolution phenotypic profiling implicates a number of protein modules in centriole duplication, ciliogenesis, and centriolar satellite biogenesis and highlights extensive interplay between these processes. By monitoring dynamic changes in the centrosome-cilium protein interaction landscape during ciliogenesis, we also identify satellite proteins that support cilia formation. Systematic profiling of proximity interactions combined with functional analysis thus provides a rich resource for better understanding human centrosome and cilia biology. Similar strategies may be applied to other complex biological structures or pathways.

Non-ribosomal factors in ribosome subunit assembly are emerging targets for new antibacterial drugs.

It is becoming increasingly clear that bacterial ribosome assembly is catalyzed by a variety of non-ribosomal factors. Newly characterized factors in bacterial ribosome biogenesis are broadly conserved and often indispensable proteins that can be classified either as chaperones facilitating assembly, or enzymes with ribosomal RNA- and ribosomal protein-modifying functions. Accumulating evidence indicates that the proteins Era, Obg, YjeQ, YlqF and RimM are chaperones which may be crucial to bacterial ribosome assembly, and therefore represent novel targets for modern antibacterial drug discovery. Ongoing work aimed at understanding ribosome biogenesis is expected to continue to yield additional factors crucial to this process, and provide new targets with drug discovery potential.

CEP120 and SPICE1 cooperate with CPAP in centriole elongation.

Centrosomes organize microtubule (MT) arrays and are comprised of centrioles surrounded by ordered pericentriolar proteins. Centrioles are barrel-shaped structures composed of MTs, and as basal bodies they template the formation of cilia/flagella. Defects in centriole assembly can lead to ciliopathies and genome instability. The assembly of procentrioles requires a set of conserved proteins. It is initiated at the G1-to-S transition by PLK4 and CEP152, which help recruit SASS6 and STIL to the vicinity of the mother centriole to organize the cartwheel. Subsequently, CPAP promotes centriolar MT assembly and elongation in G2. While centriole integrity is maintained by CEP135 and POC1 through MT stabilization, centriole elongation requires POC5 and is restricted by CP110 and CEP97. How strict control of centriole length is achieved remains unclear. Here, we show that CEP120 and SPICE1 are required to localize CEP135 (but not SASS6, STIL, or CPAP) to procentrioles. CEP120 associates with SPICE1 and CPAP, and depletion of any of these proteins results in short procentrioles. Furthermore, CEP120 or CPAP overexpression results in excessive centriole elongation, a process dependent on CEP120, SPICE1, and CPAP. Our findings identify a shared function for these proteins in centriole length control.

Systematic analysis of human protein complexes identifies chromosome segregation proteins.

Chromosome segregation and cell division are essential, highly ordered processes that depend on numerous protein complexes. Results from recent RNA interference screens indicate that the identity and composition of these protein complexes is incompletely understood. Using gene tagging on bacterial artificial chromosomes, protein localization, and tandem-affinity purification-mass spectrometry, the MitoCheck consortium has analyzed about 100 human protein complexes, many of which had not or had only incompletely been characterized. This work has led to the discovery of previously unknown, evolutionarily conserved subunits of the anaphase-promoting complex and the gamma-tubulin ring complex--large complexes that are essential for spindle assembly and chromosome segregation. The approaches we describe here are generally applicable to high-throughput follow-up analyses of phenotypic screens in mammalian cells.