As histones represent about half of the nucleoprotein complex known as chromatin, they are vital to DNA replication and the subsequent assembly of chromosomes A report of the research appears in the Aug. 29 edition of the science journal Molecular Cell.
"This is the first enzyme I'm aware of that's specific for a particular group of messenger RNAs," said Dr. William F. Marzluff, professor of biochemistry and biophysics at UNC's School of Medicine.
"We think this novel enzyme halts the synthesis of histones when they're no longer needed by rapidly degrading histone mRNAs. This is important because too much histone synthesis can be lethal to the cell."
Marzluff's focus on histone mRNA stems largely from his team's 1996 discovery and cloning of the stem-loop binding protein SLBP. A major regulatory player in histone mRNA expression, SLBP latches onto the looped tail of histone mRNA and signals the synthesis of histone proteins. In addition, SLBP remains bound to histone mRNA, making sure that its instructions are properly translated.
But SLBP's role in the rapid destruction of histone mRNA when histone synthesis is no longer needed has remained unclear. "Now we have another protein - this enzyme called 3-prime histone mRNA exonuclease - that binds to the same region and also binds to SLBP," said study lead author Dr. Zbigniew Dominski, associate professor of biochemistry and biophysics at UNC. "And they bind together in a very short region, where we had thought there was only one protein at any one time."
The protein had been identified previously but had not been characterized, Dominski said
Contact: Leslie Lang
University of North Carolina School of Medicine