Long before RAM, CDs, or vinyl were a twinkle in anyone’s eye, biology had already evolved the world’s most brilliant information storage system.
“Take a single human cell. There’s a string 3 billion letters long that stores all the information your body needs to build, repair, and change itself over the course of a lifetime,” says B.N. Queenan, Executive Director of Research at Harvard’s NSF-Simons Center for Quantitative Biology. “And somehow all that gets packed into a structure much smaller than the cross section of a human hair.”
This breath-taking cellular packing strategy is accomplished by chromosomes, the molecular complex of DNA and proteins that compact the entire genetic material of a living thing into its nucleus. A vast army of proteins seamlessly condense or expand DNA on demand, hiding certain areas while making others available, twisting, dragging, and rearranging portions of the DNA as needed. But what are the the physical tricks and tactics that make this possible?
“We wish to provide descriptions of global chromosomal processes from an entirely new perspective in which chromosomes are considered as mechanical objects,” says Nancy Kleckner, Herchel Smith Professor of Molecular Biology. “In this view, important fundamental features of chromosomal processes are manifestations of the accumulation, release and redistribution of mechanical forces (stresses) within/along/between/among chromosomes and sub-chromosomal domains.”
Capturing the delicate dynamics by which chromosomes push and pull, wind, curl, unfold and jiggle is no easy task. Chromosomes are exceedingly small, as are the forces in question.
Enter Irina Martynenko, a research fellow in Biophotonics at the Federal Institute for Materials Research and Testing in Berlin and visiting scholar at the NSF-Simons Center for Quantitative Biology at Harvard. “My research unites two strands of nanoworld inquiry,” says Martynencko. “I combine my core expertise in nanooptics/nanophotonics with investigations into the nanoscale processes occurring in living cells.”
Working with postdoctoral fellow Maria Mukhina, Martynencko is developing strategies to deliver mechanoluminescent nanocrystals into the nucleus. “These crystals are a little bit springy. They can be compressed when they are pushed on,” says Martynenko. “Then when they relax, they emit light. We want to use that emitted light to measure the forces experienced by chromosomes.”
“It’s a very ambitious project,” says Queenan. “But imagine how you’d feel if you could watch chromosomes sparkling and finally figure out what they’re up to.”