No abstract

Skp1 an essential component of the SCF (Skp1/cullin/F-box) E3 ubiquitin ligases, which target proteins for degradation by the 26S proteasome. We generated a skp1dM mutant strain that is defective for galactose induction of the GAL1 gene and we have found that galactose-induced protein degradation of the repressor Mig2 is defective in this strain. Mig2 degradation was also abolished in cells lacking the protein kinase Snf1 and the F-box protein Das1, suggesting that Snf1 triggers galactose-induced protein degradation of Mig2 by SCFDas1. Chromatin immunoprecipitation showed that Mig2 associates with the GAL1 promoter upon the galactose-induced exit of Mig1 in skp1dM cells, but not in wild-type cells, suggesting that the conditional degradation of Mig2 is required to prevent it from binding to the GAL1 promoter under inducing conditions. A galactose-stable deletion derivative of Mig2 caused a strong Mig (multi-copy inhibition of GAL gene expression) phenotype, confirming that galactose induction of the GAL1 gene requires the degradation of the repressor Mig2. Our results shed new light on the conflicting reports about the functional role of the degradation of transcriptional activators and indicate that gene expression studies interfering with proteasome degradation should take the stabilization of potential repressors into account.

No abstract

CXCL14 is a chemokine that has previously been implicated in insulin resistance in mice. In humans, the role of CXCL14 in metabolic processes is not well established, and we sought to determine whether CXCL14 is a risk susceptibility gene important in fetal programming of metabolic disease. For this purpose, we investigated whether CXCL14 is differentially regulated in human umbilical cords of infants with varying birth weights. We found an elevated expression of CXCL14 in human low birth weight (LBW) cords, as well as in cords from nutritionally restricted Macaca fascicularis macaques. To further analyze the regulatory mechanisms underlying the expression of CXCL14, we examined CXCL14 in umbilical cord-derived mesenchymal stem cells (MSCs) that provide an in vitro cell-based system amenable to experimental manipulation. Using both whole frozen cords and MSCs, we determined that site-specific CpG methylation in the CXCL14 promoter is associated with altered expression, and that changes in methylation are evident in LBW infant-derived umbilical cords that may indicate future metabolic compromise through CXCL14.