In a Science paper published online this week, an international research team reports their use of an approach for identifying chromosome segregation proteins. They write that, using gene tagging on bacterial artificial chromosomes, protein localizing, and tandem affinity-purification mass spec, the Mitocheck consortium's analysis of 100 human protein complexes has led to the elucidations of previously unseen subunits of the anaphase-promoting and -tubulin ring complexes — both critical for chromosome segregation and spindle assembly. The authors also describe the applicability of their "high-throughput follow-up analyses of phenotypic screens in mammalian cells."
Also published in Science this week, a trio of investigators reports their examination of the Thermoplasma acidophilum proteasome using methyl-transverse relaxation optimized NMR spectroscopy. They show that the "amino-terminal residues that compose the gates of the α subunits" of the proteasome. "Interconversion between these conformers on a time scale of seconds leads to a dynamic regulation of 20S CP proteolysis activity," they write.
Researchers at Stanford University and the Max Planck Institute for Terrestrial Microbiology present evidence that tumors in maize caused by Ustilago maydis require organ-specific genes in both the host and pathogen. "Phenotypic screening of U. maydis mutants deleted for genes encoding secreted proteins and maize mutants with organ-specific defects confirmed organ-restricted tumorigenesis," the authors write, adding that the infection mechanism "provides an agronomically important model of biotrophic host-pathogen interactions."
Also in Science this week, researchers in China describe the "partitioning of histone H3-H4 tetramers during DNA replication-dependent chromatin assembly." The authors report that H3.3-H4 tetramers split in vivo, while H3.1-H4 tetramers remain intact. By inhibiting DNA replication, the team reduced the amount of splitting events, supporting the notion that "'silent' histone modifications within large heterochromatic regions are maintained by copying modifications from neighboring preexisting histones without the need for H3-H4 splitting events," they write.