$720K NIH Grant to Further Professor's Genetic Research

Patricia Hilleren, Lubin Family Professor for Women in Science at Skidmore, has received a five-year, $720,000 grant from the National Institutes of Health to further her research on quality control in the nucleus of cells.

Like any good factory, living cells have quality-control systems by which many mistakes are detected and cleared up before they cause harm. Quality control for genetic processing takes place in the cell's cytoplasm and also in its nucleus – where it has been little studied to date.

A key step in the expression of genes – that is, the delivery and carrying out of their coded instructions for the synthesis of particular proteins – is the modification of "pre-messenger RNA" to generate various permutations of code. A strand of pre-mRNA resembles a train: boxcars of genetic code, called exons, are separated by linkages, called introns. In pre-mRNA processing, introns are chemically spliced out so that the exons on either side join continguously, forming a new code sequence.

The splicing is done by a complex process known as a spliceosome, which binds to an intron and excises it. But not always: If an intron is flawed or the chemistry goes awry, the spliceosome may get stalled or stuck. Not only does the splice fail, but the stuck spliceosome can't move on to its next task, and the faulty intron stays hidden from the enzymes that should clear it away. Soon, says Hilleren, "It builds like a traffic jam: wrecked cars clog the road, and the tow trucks get blocked in too. It could shut down gene expression, a potentially lethal situation." Given the number and speed of splicing operations occurring in cells all the time, such errors are not infrequent; most splicing errors are somehow detected and cleared from the cell.

In the lab Hilleren studies QC in a single-celled yeast, which "carries out the same biological processes as human cells but is much easier to manipulate," she explains. First she chemically infuses into the yeast cell a "reporter gene," so called because it can be uniquely traced. The splicing machinery will recognize that transcripts made from this reporter gene contain an intron, and they will attempt to splice it. However, the intron has been intentionally altered such that splicing will be stalled at a specific stage. Then she samples the genetic material in the cell to monitor whether the aberrant introns accumulate, indicating stalled spliceosomes, or degrade, indicating disassembly and cleanup.

In practice, what she can see are only indirect indicators: Through extensive chemical processing, the concentrations of reporter-gene components are imaged as gray bands on a white card. By varying the introduced introns or other factors, and by comparing the results of many tests and controls, Hilleren seeks to identify the agents and pathways of spliceosome disassembly that help determine the fate of ill-processed RNAs.

Co-author of a 2001 article on RNA quality control in the journal Nature, Hilleren was a researcher in the Howard Hughes Medical Institute at the University of Arizona from 1997 until 2003, when she joined Skidmore's biology faculty. She holds bachelor's degrees in microbiology and public health from St. Cloud State University and a Ph.D. in biochemistry, molecular biology, and biophysics from the University of Minnesota in Minneapolis. Her NIH research grant begins in June.

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