Humans share at least 97 percent of their genes with chimpanzees, but, as a new study of transcription factors makes clear, what you have in your genome may be less important than how you use it.

Transcription factors are proteins that bind to specific regions of the DNA to promote or repress the activity of many genes.

Previous studies have found differences in gene expression between humans and chimps, particularly in the brain. Genes involved in metabolism or protein transport, for example, are translated into mRNAs at a much higher level in human brains than in the smaller brains of chimpanzees.

This makes sense, said University of Illinois cell and developmental biology professor Lisa Stubbs, who led the new analysis with postdoctoral researcher Katja Nowick.

"These differences fit what we know because the human brain is so much larger and proteins need to be shuttled a long way out to the synapses," Stubbs said. "A higher requirement for metabolic energy has also been demonstrated independently for human brains."

What wasn't clear from previous studies was how this upsurge in gene activity was coordinated, she said.

Stubbs has had a longtime interest in the evolutionary role of transcription factors and other regulatory agents in the genome. She is particularly interested in the largest family of transcription factors in mammals, the KRAB zinc finger (KRAB-ZNF) genes, which on average have accumulated more differences in sequence between humans and chimps than other genes.

"There are a lot of unique new transcription factors that arise in this family," Stubbs said. "And they arise by duplication of older genes. So the genes make a new copy of themselves and then that new copy takes on a slightly different or even dramatically different function."

"Our very strong bias is to believe that these transcription factors are involved in speciation and traits that make species unique," she said.

Source: University of Illinois at Urbana-Champaign