If you starve a nematode worm, it will live as if in suspended animation. All growth and development ceases. That stalled activity at the level of the whole organism can be seen at the level of the genome too. The enzymes that copy DNA into RNA literally stop right where they are. Life takes pause.
“It’s as if the polymerases are preloaded in anticipation of feeding,” says Ryan Baugh, an Assistant Professor of Biology. “They are poised for a rapid response.”
Once thought to be the exception to the rule, scientists are increasingly realizing that this pausing mechanism is a more general layer of regulatory control in many organisms and its benefits might go beyond speedy responses. Paused genes could be a key reminder for a dormant cell of who it is supposed to be. That way, when conditions improve, the cell can pick up where it left off without missing a beat.
“If you have these developmental control factors bound in the genome but paused, in a sense the cell has a memory of its identity that is very stable,” Baugh says.
Genome pausing speaks to an important property of gene networks and one that is an increasing focus for systems biologists: how networks change over time. “Pausing is a crucial mechanism that can account for dynamics in gene expression,” he says. “It offers a unique way for cells to go from one state to another.”
“Rather than one gene, one process, one cell type, we try to consider several at once and what kinds of relationships they have to each other – using a combination of modeling and experiment to advance beyond what you might get with intuition alone.”
Ultimately for Baugh, systems biology comes down to a mindset. “Rather than one gene, one process, one cell type, we try to consider several at once and what kinds of relationships they have to each other – using a combination of modeling and experiment to advance beyond what you might get with intuition alone. That’s where systems biology really does offer something new and different.”