To date, some researchers have relied mostly on highly sensitive mRNA assays to study the effects of microRNAs. Because these assays measure only mRNA levels and not protein levels, researchers worried that any microRNA activity that reduced translation without reducing the mRNA would be missed, potentially skewing results.
To determine microRNAs' effects on translation and mRNA levels, Huili Guo, a graduate student in the Bartel lab, performed genome-wide ribosome profiling of human and mouse cells. This test provides a snapshot of whether or not ribosomes are sitting on the mRNA templates. The presence of ribosomes on the mRNA indicates that the mRNA is being translated.
Guo then measured the levels of mRNAs in the cell. By accounting for the change in the amount of targeted mRNAs, she could derive the microRNAs' effects at the translation level.
If microRNAs only disrupt translation, then targeted mRNA levels should be similar to those seen in controls. Also, the ribosome profile should show far fewer ribosomes on the targeted mRNAs as a result of interrupted translation. However, Guo found that the levels of the targeted mRNAs all decreased. Although the ribosome profiling indicated that translation was also slightly reduced on these mRNAs, the overall reduction in protein production was primarily due to the more greatly reduced mRNA levels.
To extend her results, Guo says other cells should be tested.
"I looked at cells that were growing u
|Contact: Nicole Giese|
Whitehead Institute for Biomedical Research