Sumo is a small protein that is attached to other proteins to regulate their function. A major class of Sumo targets are transcription factors. However, it is not well known which transcription factors are sumoylated, how sumoylation of these proteins is regulated, and how Sumo controls their function.
To begin unraveling the function of Sumo in transcription, Chymkowitch et al first determined at which genes Sumo can be detected. The results are recently published in the prestigious journal Genome research (impact factor 13.9) with Pierre Chymkowitch and Jorrit Enserink from the Department of Microbiology at the Department of Diagnostics and Invention as first and last authors respectively.
As it turned out, a major class of Sumo-enriched genes were genes involved in regulation of protein translation, particularly genes that encode components of ribosomes (ribosomal protein genes).
Using bioinformatics, they discovered that Sumo localizes to a very specific motif in the promoter regions of these genes. Surprisingly, this motif turned out to be identical to the binding site of a previously described transcription factor called Rap1.
Using various genetic and molecular biology techniques, the authors were able to show that Sumoylation of Rap1 results in recruitment of several basal transcription factors, thereby promoting activation of transcription.
Finally, ribosomomal protein genes are among the most highly expressed genes in the cell, and their transcription consumes a major portion of the cell’s resources, which is coordinated by a protein complex called TORC1. Chymkowitch et al found that cells coordinate transcription of these ribosomal protein genes through the combined activity of TORC1 and Sumo-Rap1.
In conclusion, this article provides novel insight in the molecular mechanisms by which Sumo regulates transcription in response to environmental challenges.
Sumoylation of Rap1 mediates the recruitment of TFIID to promote transcription of ribosomal protein genes.
Chymkowitch P, Nguéa P A, Aanes H, Koehler C, Thiede B, Lorenz S, Meza-Zepeda L, Klungland A, Enserink JM.
Genome Res. 2015 Mar 23. pii: gr.185793.114.
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