Pillai Group

Previous and current research

The aim of our research is to understand the molecular mechanisms by which non-coding RNAs regulate gene expression.We apply a combination of methods ranging from biochemistry, cell biology, bioinformatics and mouse genetics in these studies.

MicroRNAs (miRNAs) are an abundant class of ~21 nucleotide (nt) small non-protein-coding RNAs that function mostly as negative regulators of gene expression. Mis-expression of miRNAs has been implicated in human cancers, underscoring the relevance of these RNAs in human health. miRNAs recognise their mRNA targets by complementary base-pairing and prevent accumulation of their protein product. This is achieved by either mRNA degradation or repression of translation.We previously demonstrated that miRNAs inhibit an early step of translation initiation which then leads to accumulation of the mRNA targets in cytoplasmic granules called processing bodies (P-bodies). Our current research is aimed at understanding how miRNA homeostasis is maintained in the cell. MicroRNAs are processed from longer precursors via several intermediates and this processing is subject to several post-transcriptional regulatory mechanisms. We are investigating factors involved inmodulating miRNA biogenesis and studying their regulatory role during early development.

Approximately 40% of the mouse genome is composed of repeats that pose a considerable threat to the genome as several maintain the ability to jump from one location to another. Germline genomes are particularly vulnerable as the protective DNA methylation that silences the transposons is removed for a short period during germ cell development to allow extensive epigenetic reprogramming. Piwi-interacting RNAs (piRNAs) are ~30 nt long germline small RNAs that form the RNA-mediated component of defence mechanisms against transposons and function as part of an RNP by associating with the piwi clade of Argonaute proteins. Our aim is to understand the mechanisms of piRNA biogenesis and function. Using biochemical methods we recently identified the Tudor domain-containing protein 1 (Tdrd1) as a key component in the piRNP complex. Along with other groups in the field we have shown that piwi proteins are post-translationally modified by symmetrical dimethyl arginines, and that the recognition of these modifications via the tudor domains mediates interaction of piwi proteins with tudor proteins. In the absence of Tdrd1, the piwi protein accumulates piRNAs with an altered profile, suggesting a role in piRNA biogenesis.We are now trying to gain mechanistic understanding of how tudor proteins contribute to the piRNA pathway.

Future projects and goals

Purification of piwi proteins has uncovered additional novel factors in the pathway and these will be further characterised. Collaborations with structural groups to obtain atomic resolution structures of pathway components will add another dimension to our understanding of small RNAs. In the future we hope to use live cell imaging techniques to study assembly of RNPs in vivo and define the contribution of the individual constituents of the complex to this process. Investigation of the regulatory role of long noncoding RNAs will be another major focus of investigation in the lab.