Mediator Acts Upstream of the Transcriptional Activator Gal4

We show that Mediator, a protein originally isolated on the basis of its ability to respond to transcriptional activators, and thought to be regulated by an activator, can also be the master that controls the activator

Global effects of histone modifications

research interests include the regulation of gene transcription in yeasts and higher eukaryotic organisms, chromatin structure, signal transduction, as well as molecular mechanisms underlying protein–DNA and protein– protein interactions

Srb7p is a physical and physiological target of Tup1p

The holoenzyme of transcription integrates the positive and negative signals from the promoters of eukaryotic genes. We demonstrate that the essential holoenzyme component Srb7p is a physiologically relevant target of the global repressor Tup1p in Saccharomyces cerevisiae. Tup1p binds Srb7p in vivo and in vitro, and all genes tested that are repressed by Tup1p are derepressed when wild-type Srb7p is replaced by a mutant derivative of Srb7p that is no longer capable of interacting with Tup1p. Therefore, Srb7p is the first holoenzyme component essential for repression by Tup1p for which a physical interaction with Tup1p has been demonstrated. Furthermore, we find that Srb7p also binds Med6p and that this interaction is necessary for full transcriptional activation by different activators. Our finding that Med6p and Tup1p compete for the interaction with Srb7p suggests a model for Tup1p-mediated repression

The TATA-binding protein is not an essential target of the transcriptional activators Gal4p and Gcn4p in Saccharomyces cerevisiae.

According to the recruitment model, transcriptional activators work by increasing the local concentration of one or several limiting factors for the transcription process at the target promoter. The TATA-binding protein Tbp1 has been considered as a likely candidate for such a limiting factor. We have used a series of Gal4p and Tbp1 mutants to correlate the in vivo interaction between the two proteins with the strength of activation. We find a clear correlation between activation strength and in vivo interaction for the series of Gal4p mutants. Consistently, the weaker activator Gcn4p does not interact with Tbp1. However, a corresponding analysis of the series of Tbp1 mutants revealed that Tbp1 is not an essential target of the acidic activators Gal4p and Gcn4p. Furthermore, detailed analysis of a Tbp1 mutant deficient for transcriptional activation by Gal4p revealed that the mutant is defective in interactions with five other proteins involved in the process of transcription

Fumarase is involved in DNA double-strand break resection through a functional interaction with Sae2

10.1007/s00294-017-0786-4Current Genetics643697-71

Ubiquitination Occurs in the Mitochondrial Matrix by Eclipsed Targeted Components of the Ubiquitination Machinery

Ubiquitination is a critical type of post-translational modification in eukaryotic cells. It is involved in regulating nearly all cellular processes in the cytosol and nucleus. Mitochondria, known as the metabolism heart of the cell, are organelles that evolved from bacteria. Using the subcellular compartment-dependent α-complementation, we detect multiple components of ubiquitination machinery as being eclipsed distributed to yeast mitochondria. Ubiquitin conjugates and mono-ubiquitin can be detected in lysates of isolated mitochondria from cells expressing HA-Ub and treated with trypsin. By expressing MTS (mitochondrial targeting sequence) targeted HA-tagged ubiquitin, we demonstrate that certain ubiquitination events specifically occur in yeast mitochondria and are independent of proteasome activity. Importantly, we show that the E2 Rad6 affects the pattern of protein ubiquitination in mitochondria and provides an in vivo assay for its activity in the matrix of the organelle. This study shows that ubiquitination occurs in the mitochondrial matrix by eclipsed targeted components of the ubiquitin machinery, providing a new perspective on mitochondrial and ubiquitination research