| Summary: | The interplay between poly(A) tail length and miRNA regulation has been previously studied. Moretti et al., (2012) found that longer poly(A) tail lengths correlated with greater miRNA mediated repression, with miRISC association triggering the displacement of PABP from the poly(A) tail. This is in agreement with Rissland et al., (2017) who found that miRISC has the ability to alter the composition of the mRNP, in particular the association of PABP and eIF4G while not impacting on poly(A) tail length. On the other hand, Eisen et al., (2020), found that miRNAs only stimulated deadenylation of transcripts with very short poly(A) tails.
However, the interaction between poly(A) tail length and miRNA regulation has not been investigated within the context of a biological system with physiologically relevant poly(A) tail changes. As such, this project aimed to investigate how miRNA regulation is changing over the course of inflammation and how the changing poly(A) tail lengths of key inflammatory mediators may be affecting miRNA regulation.
Through the use of inhibition and overexpression studies as well as Ago2 immunoprecipitation, this study has established that TNF is regulated by miR-181a and that this regulation is changing over the course of the inflammatory response. However, the changing poly(A) tails of TNF mRNA are not affected by miR-181a regulation.
Interestingly, through the use of siRNA knockdown this study has made a novel discovery that the non-canonical polymerases TENT4A and TENT4B are required for maintenance of high TNF mRNA levels later in the inflammatory response, but more work is required to elucidate their mechanism of action.
Furthermore, a tetracycline inducible cell line was successfully generated, providing a useful tool for investigation of miR-181a regulation via the TNF 3’UTR with transcriptional induction outside of the numerous other processes that are occurring within inflammation.
Overall, the investigations within this study have provided a greater understanding of miRNA regulation of TNF mRNA and how this is changing over the course of inflammation.
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