Protein Modifiers of Gene Expression Linked to Cancer

Researchers into the molecular basis of cancer have found that the Bre1 protein controls the activity of the Rad6 protein, which modifies chromosomal DNA and effects gene expression. These findings were reported in the January 2003 issue of Molecular Cell.

Chromatin immunoprecipitation experiments conducted by investigators at St. Louis University (MO, USA) indicated that both Rad6 and Bre1 were recruited to a promoter. Bre1 was essential for this recruitment of Rad6 and was dedicated to the transcriptional pathway of Rad6. Their results suggested that Bre1 was the likely E3 enzyme that directed Rad6 to modify chromatin and ultimately to affect gene expression.


The modification of Rad6 was due to the E3 property of Bre1. An E3 enzyme binds activated ubiquitin to a target protein via formation of an amide bond with its carboxy-terminal glycine residue linked to the lysine side chain of the target protein. There are hundreds of different and distinct E3 complexes that recognize specific amino acid sequences of target proteins.

"This opens the door for further study of this protein in the regulation of gene expression,” explained senior author Dr. Ali Shilatifard, an associate professor of biochemistry and molecular biology at St. Louis University School of Medicine. "Once we understand the normal, we will have a better understanding of where something is going wrong. This, in turn, could lead to ways to block the pathway and ultimately could stop cancer development.”




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