Here, we dissected the regulatory mechanisms underlying the activity of a conserved distal promoter element 1. We show that this element carries three Sox-binding sites, works as an enhancer in vivo, and allows promoter activation by the Sox5/6/9 chondrogenic trio. In early steps of chondrogenesis, declining Hmgb1 expression overlaps with the onset of Sox9 expression. Unlike repression in late steps, Hmgb1 overexpression in early chondrogenesis
increases Matn1 promoter activation by the Sox trio, and forced Hmgb1 expression in COS-7 cells facilitates induction of Matn1 expression by the Sox trio. The conserved Matn1 control elements bind Hmgb1 and SOX9 with opposite efficiency in vitro. They show higher HMGB1 than SOX trio
occupancy in established chondrogenic cell lines, and HMGB1 silencing greatly increases MATN1 and COL2A1 Staurosporine TGF-beta/Smad inhibitor expression. Together, these data thus suggest a model whereby Hmgb1 helps recruit the Sox trio to the Matn1 promoter and thereby facilitates activation of the gene in early chondrogenesis. We anticipate that Hmgb1 may similarly affect transcription of other cartilage-specific genes. (C) 2013 Elsevier B.V. All rights reserved.”
“Yeast replication checkpoint mutants, lose viability following transient exposure to hydroxyurea, a replication-impeding drug. In all effort to understand the Selonsertib basis for this lethality, we discovered that different events are responsible for inviability in checkpoint-deficient cells harboring mutations ill the mec1 and rad53 genes. By monitoring genomewide replication dynamics of cells exposed to hydroxyurea, we show that cells with a checkpoint deficient allele of RAD53, rad53K227A, fail to duplicate centromeres. Following removal of the drug, however, rad53K227A cells recover substantial
DNA replication, including replication through centromeres. Despite this recovery, the rad53K227A mutant fails to achieve biorientation of sister centromeres during recovery from hydroxyurea, leading to secondary activation of the spindle assembly checkpoint (SAC), aneuploidy, and lethal chromosome segregation errors. We demonstrate that cell lethality from this segregation defect could be partially remedied by reinforcing bipolar attachment. In contrast, cells with the mec1-1 sml1-1 mutations AZD8931 datasheet suffer from severely impaired replication resumption upon removal of hydroxyurea. mec1-1 sml1-1 cells call, however, duplicate at least some of their centromeres and achieve bipolar attachment, leading to abortive segregation and fragmentation of incompletely replicated chromosomes. Our results highlight the importance of replicating yeast centromeres early and reveal different mechanisms of cell death due to differences in replication fork progression.”
“Stem cells have become one of the “buzz” topics in the last decade or so. One of the best systems to study adult stem cells in vivo is in the model organism, Drosophila melanogaster.