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Med8, Med18, and Med20 subunits of the Mediator head domain are interdependent upon each other for folding and complex formation
Umeå universitet, Medicinska fakulteten, Institutionen för medicinsk kemi och biofysik. (Stefan Björklund)
Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen. (Pernilla Wittung-Stafshede)
Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen. (Pernilla Wittung-Stafshede)
Umeå universitet, Medicinska fakulteten, Institutionen för medicinsk kemi och biofysik. (Stefan Björklund)
2009 (Engelska)Ingår i: Proceedings of the National Academy of Sciences of the United States of America, ISSN 0027-8424, E-ISSN 1091-6490, Vol. 106, nr 49, s. 20728-20733Artikel i tidskrift (Refereegranskat) Published
Abstract [en]

We have studied folding and complex formation of the yeast mediator head-module protein subunits Med8, Med18, and Med20. Using a combination of immunoprecipitation, far-UV circular dichroism, and fluorescence measurements on recombinantly expressed and denatured proteins that were allowed to renature separately or in different combinations, we found that Med8, Med18, and Med20 can fold in different ways to form both soluble monomeric proteins and different distinct subcomplexes. However, the concurrent presence of all three protein subunits during the renaturation process is required for proper folding and trimer complex formation.

Ort, förlag, år, upplaga, sidor
2009. Vol. 106, nr 49, s. 20728-20733
Nationell ämneskategori
Biokemi och molekylärbiologi
Forskningsämne
biokemi
Identifikatorer
URN: urn:nbn:se:umu:diva-29965DOI: 10.1073/pnas.0907645106OAI: oai:DiVA.org:umu-29965DiVA, id: diva2:278772
Tillgänglig från: 2009-11-30 Skapad: 2009-11-30 Senast uppdaterad: 2018-06-08Bibliografiskt granskad
Ingår i avhandling
1. Dynamics of protein folding and subunit interactions in assembly of the yeast mediator complex
Öppna denna publikation i ny flik eller fönster >>Dynamics of protein folding and subunit interactions in assembly of the yeast mediator complex
2009 (Engelska)Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
Abstract [en]

The Mediator complex was originally discovered in the yeast Saccharomyces cerevisiae and has since then been shown to be required for transcriptional regulation both in vitro and in vivo. The Mediator complex also stimulates basal, unregulated transcription and serves as a bridge by conveying signals from promoter-bound transcriptional regulatory proteins such as activators and repressors to the RNA Polymerase II general transcriptional machinery. The Mediator consists of 21 subunits and can be divided into three distinct modules head, middle and tail.

Despite the tremendous progress that has been achieved so far in characterizing the Mediator complex both functionally and structurally, many aspects of the complex are not yet well understood. The objective of this work is to achieve further understanding of the Mediator complex by studying the folding of different protein subunits, their interactions and how that affects assembly of the Mediator complex.

In our first study we made a temperature-sensitive med21 mutant and used it to identify genes that can suppress the mutation when present in high copy number. Among the 10 genes that we identified, the strongest suppressors were Med7 and Med10, which encode Mediator subunits, and Ash1, which encodes a repressor of the HO gene. We also used 2-hybrid experiments and immunoprecipitation to study protein-protein interactions between Med21 and the Med4, Med7 and Med10 proteins which are all essential for viability and located within the middle domain of the Mediator complex. We found that the N-terminal 2-8 amino acids of Med21 are required for interactions with Med7 and Med10. These results led us to propose a model in which the N-terminal part of Med21 functions as a molecular switchboard where competing signals from various activators, repressors and mediator subunits are integrated prior to reaching the general transcription machinery.

In our second study, we extended our studies of protein-protein interactions to another part of the mediator complex by studying the folding and the assembly processes of the mediator head domain subunits Med8, Med18 and Med20. Using purified proteins and a combination of several different methods such as immunoprecipitation, far-UV circular dichroism and fluorescence, we demonstrated that the Med8, Med18 and Med20 subunits are interdependent on each other for proper folding and complex formation.

Ort, förlag, år, upplaga, sidor
Umeå: Umeå university, 2009. s. 44
Serie
Umeå University medical dissertations, ISSN 0346-6612 ; 1290
Nyckelord
mediator, transcriptional regulation, assembly, folding
Nationell ämneskategori
Medicin och hälsovetenskap
Forskningsämne
medicinsk biokemi
Identifikatorer
urn:nbn:se:umu:diva-29976 (URN)978-91-7264-854-8 (ISBN)
Disputation
2010-01-12, KB3B1, KBC house, 901 87 Umeå, Umeå University, 10:00 (Engelska)
Opponent
Handledare
Tillgänglig från: 2009-12-21 Skapad: 2009-11-30 Senast uppdaterad: 2009-12-21Bibliografiskt granskad

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Shaikhibrahim, ZakiRahaman, HamidurWittung-Stafshede, PernillaBjörklund, Stefan

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Shaikhibrahim, ZakiRahaman, HamidurWittung-Stafshede, PernillaBjörklund, Stefan
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Institutionen för medicinsk kemi och biofysikKemiska institutionen
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Proceedings of the National Academy of Sciences of the United States of America
Biokemi och molekylärbiologi

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