Dual role of Lin28a in the regulation of miRNA biogenesis during neuronal differentiation
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Date
28/06/2016Author
Nowak, Jakub Stanislaw
Metadata
Abstract
Many cellular functions depend on the tightly regulated expression of
various proteins. Canonical control of the protein expression is associated
with transcriptional regulation. However, the small non-coding RNAs
called microRNAs (miRNAs) were identified as post-transcriptional
regulators of gene expression. In a typical manner, miRNAs originate
similarly to the coding RNAs and are processed in a multi-step maturation
process. It has been shown that miRNAs are very important for the proper
functioning of tissues. Interestingly, the human nervous system contains
over 70% of all miRNAs; thus, the maturation process has to be tightly
regulated. However, despite the important role of miRNAs, little is known
about the mechanisms regulating their biogenesis. In my PhD project, I
showed that during early stages of neuronal differentiation, Lin28a
controls levels of neuro-specific miRNA-9. I demonstrated that Lin28a
binds to the conserved terminal loop (CTL) of pre-miRNA-9 and decreases
the cellular levels of miRNA-9 during retinoic acid-mediated neuronal
differentiation of mouse teratocarcinoma P19 cells. I revealed that the
Lin28a-mediated inhibition of miRNA-9 production was uridylation-independent.
Furthermore, constitutive expression of GFP-tagged Lin28a
reduced the levels of let-7a but not miRNA-9, whereas untagged Lin28a
inhibited both miR-9 and let-7a during the course of neuronal
differentiation. Using small RNAseq analysis of P19 cells with constitutive
expression of Lin28a I showed that it controls many more miRNAs than
previously recognised. Intriguingly, many miRNAs were upregulated by
Lin28a overexpression. I demonstrated with high-throughput, the limited
function of GFP-tagged Lin28a results, and I also showed that untagged
Lin28a inhibits the production of a number of brain-specific miRNAs
including miRNA-9. Finally, I revealed that 3’-5’exoribonuclease Dis3l2
was responsible for uridylation-independent degradation of pre-miRNA-9. Altogether, my results provided evidence that Lin28a has both positive
and negative roles in the regulation of miRNA production and has a dual
role in triggering pre-miRNA degradation.
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