But to make his observations, Hockert had to employ what co-investigator Clinton MacDonald calls "a trick."
"Andrew realized we can make a version of the protein that is different than the regular version already in the cell. We can mutate it," says MacDonald, an associate professor at Texas Tech who oversaw Hockert's work. "And, if you put that mutated version of the protein in the cell, it only works on the genes we tell it to work on and not the rest. So, it doesn't kill the cell."
Having come up with a clever way to study and measure different aspects of the protein in a living cell, MacDonald says, the team then had to pick one in particular on which to focus.
"The feature Andrew chose to examine was how CstF-64 interacted with another polyadenylation protein and how that interaction allowed both those proteins to work inside the nucleus," MacDonald says.
As important as CstF-64 is to gene expression, it doesn't exactly have "VIP" status when it comes to gaining access to the nucleus. Lacking what is known as a nuclear localization signal, it has to rely on its partner protein, CstF-77, to lead the way to and get in the door.
"We already knew the sequence of our protein, CstF-64, and so we knew it didn't have a special signal to get it in the nucleus. So, we hypothesized something else was dragging it in, and the most likely thing was a partner protein working alongside it," Hockert explains.
With the mutant version of the protein in place, the team soon discovered their hypothesis was correct: CstF-64 had to bind with CstF-77 to get into the cell's command center. Furthermore, MacDonald says, the team was able to report which piece of CstF-64 binds with its partner "the hinge domain."
Having overcome the cell-death obstacle and having confirmed the significance of the "hinge" domain for nuclear localization, the researchers expect th
|Contact: Angela Hopp|
American Society for Biochemistry and Molecular Biology