Final Report Summary - SRNAS (Small non-coding RNAs in cell function and disease)
MiRNAs have been implicated in a variety of diseases including cancer. To date, almost all types of cancer have been analyzed for miRNA expression and in many cases distinct miRNA profiles have been reported. Moreover, oncogenes such as RAS or BCL2 are controlled by the miRNA pathway and alterations in miRNA expression results in up-regulation of these oncogenes. MiRNAs can therefore function as tumor suppressors. Reciprocally, miRNAs have also been reported to function as oncogenes.
In many tumors, cells with stem cell-like properties have been identified. In the light of these findings, the cancer stem cell hypothesis has been proposed, which suggests that cancers contain a small fraction of cancer cells that constitute a reservoir of cells that are capable of self-renewal and tumor maintenance. In sub-project 1, we analyzed miRNAs in glioblastoma stem cells. Glioblastoma are highly malignant and fatal tumors. We found that miR-9/9* and miR-17 are highly abundant in these cells and inhibition of these miRNAs leads to reduced tumor growth in vitro. As part of the project, we characterized the entire regulatory network generated by these miRNAs and provide the basis for potential therapeutic intervention.
In sub-project 2, we aimed at the identification of novel classes of small RNAs in human cells. Small RNA cloning and sequencing approaches that had been done so far aimed at the identification of differentially expressed miRNAs or new classes of small regulatory RNAs. However, large numbers of the sequence reads in almost all sequencing data sets have been considered “degradation products” because they originated from larger RNA species. By immunoprecipitating Argonaute proteins (the direct binding partners of miRNAs in all species), we have recently found that larger non-coding RNAs such as small nucleolar RNAs (snoRNAs) can be processed to functional small regulatory RNAs. Our cloning data further indicates that there are many other classes of non-coding RNAs including tRNAs, scRNAs and rRNAs that are processed and specifically loaded onto Ago proteins. Using Argonaute-small RNA complex isolation approaches we characterized the small RNA interactome of Argonaute proteins in detail. Strikingly, we found a specific tRNA-miRNA hybrid that can give rise to a functional tRNA but also a functional miRNA depending on the cellular environment. This is clearly one highlight of our project and will be further characterized in the future.
In many tumors, cells with stem cell-like properties have been identified. In the light of these findings, the cancer stem cell hypothesis has been proposed, which suggests that cancers contain a small fraction of cancer cells that constitute a reservoir of cells that are capable of self-renewal and tumor maintenance. In sub-project 1, we analyzed miRNAs in glioblastoma stem cells. Glioblastoma are highly malignant and fatal tumors. We found that miR-9/9* and miR-17 are highly abundant in these cells and inhibition of these miRNAs leads to reduced tumor growth in vitro. As part of the project, we characterized the entire regulatory network generated by these miRNAs and provide the basis for potential therapeutic intervention.
In sub-project 2, we aimed at the identification of novel classes of small RNAs in human cells. Small RNA cloning and sequencing approaches that had been done so far aimed at the identification of differentially expressed miRNAs or new classes of small regulatory RNAs. However, large numbers of the sequence reads in almost all sequencing data sets have been considered “degradation products” because they originated from larger RNA species. By immunoprecipitating Argonaute proteins (the direct binding partners of miRNAs in all species), we have recently found that larger non-coding RNAs such as small nucleolar RNAs (snoRNAs) can be processed to functional small regulatory RNAs. Our cloning data further indicates that there are many other classes of non-coding RNAs including tRNAs, scRNAs and rRNAs that are processed and specifically loaded onto Ago proteins. Using Argonaute-small RNA complex isolation approaches we characterized the small RNA interactome of Argonaute proteins in detail. Strikingly, we found a specific tRNA-miRNA hybrid that can give rise to a functional tRNA but also a functional miRNA depending on the cellular environment. This is clearly one highlight of our project and will be further characterized in the future.