Male-specific lethal complex in Drosophila counteracts histone acetylation and does not mediate dosage compensation
Lin Sun, Harvey R. Fernandez, Ryan C. Donohue, Jilong Li, Jianlin Cheng, and James A. Birchler
A popular hypothesis to explain dosage compensation of the X chromosome in male Drosophila is that a histone acetylase is brought to the chromosome by the MSL complex and increases H4 lysine16 acetylation, which mediates the increased expression. We investigated (pp. E808–E817) the properties of the MSL complex with a series of specific gene-targeting and global gene-expression experiments. The data indicate that the MSL complex does not mediate dosage compensation directly, but rather, its activity overrides the high level of histone acetylation and counteracts the potential overexpression of X-linked genes to achieve the proper twofold up-regulation in males.
Deubiquitinase function of arterivirus papain-like protease 2 suppresses the innate immune response in infected host cells
Puck B. van Kasteren, Ben A. Bailey-Elkin, Terrence W. James, Dennis K. Ninaber, Corrine Beugeling, Mazdak Khajehpour, Eric J. Snijder, Brian L. Mark, and Marjolein Kikkert
Many viruses encode proteases that cleave both viral and host substrates. Arteriviruses encode such a dual-specificity protease (PLP2) that removes ubiquitin from cellular proteins involved in host immunity. Based on a 3D structure of PLP2, we engineered (pp. E838–E847) the protease to have diminished deubiquitinating activity without affecting its activity toward its viral substrate. Viruses expressing such engineered proteases displayed a significantly weakened ability to evade host immune responses. This result demonstrates a crucial role for PLP2 in arterivirus immune evasion and opens new possibilities for developing improved attenuated virus vaccines against economically important arteriviruses and other viruses encoding similar dual-specificity proteases.
Coupling mutagenesis and parallel deep sequencing to probe essential residues in a genome or gene
William P. Robins, Shah M. Faruque, and John J. Mekalanos
In this work (pp. E848–E857) we present a technique called Mut-seq. We show that a very large population of genomes or genes can be mutagenized, selected for growth, and then sequenced to determine which genes or residues are probably essential. Here we have applied this method to T7 bacteriophage and T7-like virus JSF7 of Vibrio cholerae. All essential T7 genes have been previously identified and several DNA replication and transcription proteins have solved structures and are well studied, making this a good model. We use this information to correlate mutability at protein residues with known essentiality, conservation, and predicted structural importance.