Molecular Genetics and Genomics

, Volume 276, Issue 2, pp 197–210

Functional and physical interactions within the middle domain of the yeast mediator

  • Magnus Hallberg
  • Guo-Zhen Hu
  • Susanna Tronnersjö
  • Zaki Shaikhibrahim
  • Darius Balciunas
  • Stefan Björklund
  • Hans Ronne
Original Paper

DOI: 10.1007/s00438-006-0135-7

Cite this article as:
Hallberg, M., Hu, GZ., Tronnersjö, S. et al. Mol Genet Genomics (2006) 276: 197. doi:10.1007/s00438-006-0135-7

Abstract

Med21 (Srb7) is a small essential subunit of the middle domain of the Mediator, which is conserved in all eukaryotes. It is thought to play an important role in both transcriptional activation and repression. In the yeast Saccharomyces cerevisiae, Med21 is known to interact both with the Mediator subunit Med6 and the global co-repressor Tup1. We have made a temperature-sensitive med21-ts mutant, which we used in a high copy number suppressor screen. We found ten yeast genes that can suppress the med21-ts mutation in high copy number. The three strongest suppressors were MED7 and MED10 (NUT2), which encode other Mediator subunits, and ASH1, which encodes a repressor of the HO gene. 2-Hybrid experiments confirmed multiple interactions between Med21, Med10, Med7 and Med4, and also revealed a Med21 self-interaction. The interactions of Med21 with Med7 and Med10 were verified by co-immunoprecipitation of tagged proteins produced in insect cells and E. coli, where both interactions were found to depend strongly on the amino acid residues 2–8 of Med21. These interactions, and the interactions of Med21 with Med6 and Tup1, suggest that Med21 may serve as a molecular switchboard that integrates different signals before they reach the core polymerase.

Keywords

Med7Med10Med21MediatorNut2Srb7

Copyright information

© Springer-Verlag 2006

Authors and Affiliations

  • Magnus Hallberg
    • 1
    • 4
  • Guo-Zhen Hu
    • 2
    • 3
  • Susanna Tronnersjö
    • 2
    • 3
  • Zaki Shaikhibrahim
    • 1
  • Darius Balciunas
    • 2
    • 3
    • 5
  • Stefan Björklund
    • 1
  • Hans Ronne
    • 2
    • 3
  1. 1.Department of Medical Biochemistry and BiophysicsUmeå UniversityUmeåSweden
  2. 2.Department of Medical Biochemistry and MicrobiologyUppsala UniversityUppsalaSweden
  3. 3.Department of Plant Biology and Forest GeneticsSwedish University of Agricultural SciencesUppsalaSweden
  4. 4.Institute of Reproductive and Developmental Biology, Hammersmith Campus Imperial CollegeLondonUK
  5. 5.Department of Genetics, Cell Biology and DevelopmentUniversity of MinnesotaMinneapolisUSA