In Cell this week, investigators at the Stowers Institute for Medical Research in Kansas City, Mo., show that "the ATAC acetyltransferase complex coordinates MAP kinases to regulate JNK target genes." Specifically, the team found that "ATAC subunits are required for c-Jun occupancy of these genes and for H4K16 acetylation at the Jra enhancer, promoter, and transcribed sequences." In addition, ATAC co-localizes with c-Jun, the team shows, and recruits the upstream kinases Misshpane, MKK4, and JNK, which suppress further JNK activation. "ATAC governs the transcriptional response to MAP kinase signaling by serving as both a co-activator of transcription and as a suppressor of upstream signaling," the authors conclude.
Researchers at the Washington University School of Medicine report in Cell this week that the leader RNA of the Mg2+ transporter gene mgtA in Salmonella enterica "harbors an 18-codon proline-rich open reading frame — termed mgtL — that permits intracellular proline to regulate mgtA expression." When the team perturbed mgtL translation by genetic, pharmacological, and environmental means, they found an increase in the mRNA levels from the mgtA coding region. "Substitution of the mgtL proline codons by other codons abolished the response to proline and to hyperosmotic stress but not to Mg2+," the authors write, adding that their data suggest that an mRNA leader can "employ different mechanisms to sense disparate intracellular signals."
A trio of scientists from Stowers examines histone crosstalk, posttranslational modifications, and resulting transcriptional outcomes. "Recent studies indicate that histone modifications have context-dependent effects, making their interplay more like a language within the chromatin signaling pathway than a code," the authors opine, adding that "future progress will require us to learn much more about how the words comprising the dictionary of histone crosstalk are used."
A research team led by the Wellcome Trust Centre for Cell Biology's Shinya Ohta has determined the protein composition of mitotic chromosomes using multi-classifier combinatorial proteomics. Ohta et al. describe their approach, which "integrated quantitative proteomics with bioinformatic analysis to generate a series of independent classifiers that describe the [approximately] 4,000 proteins identified in isolated mitotic chromosomes." In their subsequent whole-chromosome proteome analysis, the team found — via Ska3/Rama1 genetic knockouts — "that the APC/C and RanBP2/RanGAP1 complexes depend on the Ska complex for stable association with chromosomes." The authors predict that they've yet to discover up to 97 novel centromere-associated proteins using their data set.