|Home | About | Journals | Submit | Contact Us | Français|
Ubiquitylation of K123 of Saccharomyces cerevisiae histone H2B (H2BK123-Ub) is associated with active transcription and is a prerequisite for histone H3 K4 methylation. Zheng et al. (p. 3635-3645) have identified a region within histone H2A, the HAR domain, important for H2BK123-Ub. The HAR domain is adjacent to K123 of H2B in the nucleosome and may form a surface recognized by the ubiquitylation machinery. Interestingly, the HAR domain is partially buried under nucleosomal DNA and its accessibility would require transcription-linked alterations to the nucleosome. This study identifies a novel trans-tail regulatory pathway and suggests a mechanism for restricting H2BK123-Ub to transcribed regions of the genome.
PDK1-Akt signaling in tumorigenesis and glucose metabolism has been extensively investigated. However, the function of this signaling pathway in embryonic development, in particular in cardiovascular development, needs to be explored. Using mouse models, Feng et al. (p. 3711-3721) deleted PDK1 specifically in endothelial cells and found embryonic lethality at around embryonic day 11. Cardiovascular development is severely impaired, with defective vascular remodeling and abnormal epithelial-mesenchymal transition (EMT) in the atrioventricular canal. Overexpression of constitutively active Akt and Snail could rescue EMT defects in an ex vivo culture system. This work demonstrates that PDK1-Akt signaling is an essential regulator in cardiovascular development.