Researchers look for cancer cure in cell division study

Huntsman Cancer Institute researchers are studying how cells divide and what regulates cell division.

By understanding how cells divide, researchers can find ways to stop cell divisions to prevent cancerous cells from spreading, members of the study said.

Cell division requires each part of a cell to double so that each new cell has every necessary part, including a complete set of DNA, to regulate its function.

When the nucleus, or center of the cell containing the DNA, prepares to double and divide, the membrane around the nucleus, called the nuclear envelope, needs to disassemble.

Researchers were previously puzzled by how this occurs. Some believed that the nuclear envelope merges with another membrane in the cell, called the endoplasmic reticulum, creating one large membrane that splits in two during cell division, researchers said.

But others, including Katharine Ullman, assistant professor of oncological sciences and Huntsman Cancer Institute investigator, says she believed the nuclear membrane breaks into small pieces called vesicles. During cell division, half of these vesicles go to each new cell.

To understand how the membrane disassembles before division, scientists needed to know what triggers the membrane to do so and how, she said.

To unlock this mystery, Ullman and her team of researchers began by trying to better understand a protein in the nuclear envelope that is part of a portal letting molecules in and out of the nucleus. The protein is called Nup153, she said.

To do their research, Ullman’s team began by injecting a frog with a hormone that caused it to lay all of its eggs at the same time.

They then crushed all the eggs in a beaker. A frog egg is a stockpile of cellular material. It has all the raw materials needed for an egg to split into thousands of tiny cells to form a frog embryo, Ullman said.

The researchers found, to their surprise, that before division of the nucleus, the portal protein Nup153 was interacting with a protein complex, called Coatomer I, which forms vesicles from membranes in other parts of the cell.

Coatomer I “coats” a membrane and pinches it off to create capsule-like vesicles that can transport materials to different parts of the cell.

If Coatomer I was interacting with the portal protein before cell division, it most likely was doing so to break the nuclear envelope into vesicles, Ullman said. This would confirm the vesicle theory of how the membrane disassembles.

To confirm their assumption, Ullman’s team prohibited Coatomer I from interacting with the portal protein, and the membrane did not break up.

Besides discovering how the membrane breaks up, the discovery also taught the researchers that the portal protein, Nup153, was doing more than just transporting molecules in and out of the nucleus.

“We had to rethink what Nup153 was doing,” Ullman said.

The portal protein has an unexpectedly essential role in the preparation of the membrane for division, she said.

One reason for understanding these minute details, Ullman said, is to learn how to control cell division.

When scientists know how to control cell division, they can stop the spread of cancer within the body, Ullman said.

The discovery from the study was published Sept. 8 in the journal Developmental Cell.

Ullman’s fellow researchers were Jin Liu, Amy Prunuske and Ammon Fager.

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