Violette Charteau

Foto Violette Violette.Charteau[at]
+31(0)24 3613686
Lab 6.15

Towards a comprehensive understanding of the biochemical function of the human RNase MRP

RNase MRP is an essential endoribonuclease found in all eukaryotic cells. RNase MRP is a ribonucleoprotein (RNP) complex that accumulates in the nucleoli. Ten different proteins and a single RNA component have been found to be associated with the human RNase MRP. Mutations in the RNA component (RMRP) cause cartilage hair hypoplasia (CHH), a rare pleiotropic disease. CHH is characterized by a short stature and hypoplastic hair. Moreover, immune deficiencies, Hirschsprung disease and an increased risk for developing certain types of cancer are observed in CHH patients.

Over the years many efforts have been taken to identify RNase MRP substrates. So far, the precursor of ribosomal RNA, cyclin B2 mRNA and viperin mRNA have been identified as substrates, but evidence for cyclin B2 mRNA cleavage is ambiguous. The identification of substrates is complicated by the fact that RNase MRP is structurally highly similar to RNase P, another essential endoribonuclease. RNase MRP and RNase P have distinct RNA components but share all their protein subunits in humans, making it difficult to isolate RNase MRP and RNase P separately.

The main goal of my project is to characterize the biochemical function of the human RNase MRP complex.
A first objective is to identify new RNase MRP substrates. This would lead to increased knowledge of the biochemical function and may provide insight in pathophysiological aspects of RNase MRP. For this, I will use data obtained with various technologies previously applied in the lab, including RNA tagging, immunoaffinity purification, and a combination of UV-crosslinking, tandem affinity purification, and (high-throughput) analysis of cDNAs (CRAC). These procedures yielded datasets of RNAs potentially targeted by the human MRP RNase. A RMRP knock-out cell line and highly sensitive RNA detection methods are being developed to validate these results and to study the conversion of potential substrate RNAs in more detail.
More information on functional activities may also be obtained by the identification of protein interaction partners, including unique protein subunits of the MRP RNase. In yeast, the MRP RNase shares most of its proteins components with RNase P but contains 2 unique protein subunits. Potential unique proteins components and interacting proteins of the human MRP complex have been identified using immunoaffinity-purification and mass spectrometry analysis and need to be validated. Identification of a unique protein subunit of the human RNase MRP would increase our understanding of this RNP, as well as facilitate the study of RNase MRP and RNase P by making it easier to isolate and differentiate between them.
Recently, circular forms of RMRP have been identified. The last part of my project is focused on the generation and function of these circular isoforms in human cells.


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