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Updated: Jun 15, 2025

Assessment of Selective mRNA Translation in Mammalian Cells by Polysome Profiling
Published on: October 28, 2014
Proteomic Profiling of Unannotated Microproteins in Human Placenta Reveals XRCC6P1 as a Potential Negative Regulator
Qiong Li1,2, Fanrong Liu3, Xiaoyu Ma4
1Department of Obstetrics and Gynecology, The First People's Hospital of Chenzhou, Chenzhou 423000, China.
Abstract:
Ribosome profiling and mass spectrometry have revealed thousands of previously unannotated small and alternative open reading frames (sm/alt-ORFs) that are translated into micro/alt-proteins in mammalian cells. However, their prevalence across human tissues and biological roles remains largely undefined. The placenta is an ideal model for identifying unannotated microproteins and alt-proteins due to its considerable protein diversity that is required to sustain fetal development during pregnancy. Here, we profiled unannotated microproteins and alt-proteins in human placental tissues from preeclampsia patients or healthy individuals by proteomics, identified 52 unannotated microproteins or alt-proteins, and demonstrated that five microproteins can be translated from overexpression constructs in a heterologous cell line, although several are unstable. We further demonstrated that one microprotein, XRCC6P1, associates with translation initiation factor eIF3 and negatively regulates translation when exogenously overexpressed. Thus, we revealed a hidden sm/alt-ORF-encoded proteome in the human placenta, which may advance the mechanism studies for placenta development as well as placental disorders such as preeclampsia.
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