Lecture 16 – Overview of sRNA Signaling

BIOL 5190/6190 Cellular & Molecular Singal TransductionPrepared by Bob Locy

Last modified -13F

Introductory

• Brief History of sRNAs• Bacterial – riboswitches• Eukaryotes –

• miRNA synthesis & function• Plant paradigm• Animal paradigm

• siRNA synthesis & function• Plant paradigm• Animal paradigm

Introductory

• Brief History of sRNAs• lin-4 – C. Elegans in 1993 – turned out to be the first small regulatory RNA to be

discovered in eukaryotes.• Mutant with developmental defects – Animals look terrible, elogated growth,

larval skin, stop molting, apparently partial larval growth arrest • Independently, RNA interference (RNAi) was discovered• RNAi involved in control of viral pathogenesis, and artificial RNAi for study of

gene regulation.• Ultimately demonstrated that “natural” RNAi was viable regulatory process, and• The discovery of multiple small regulatory RNAs in eukaryotes, and post

transcriptional gene silencing, translational gene silencing, and transcriptional gene silencing.

Introductory

• Brief History of sRNAs• RNAi – Post transcriptional gene silencing.• Originally discovered in transgenic plants, as antisense knockdown of

transcription• Led to the discovery of hairpins as RNAi agents• Ultimately, found natural antisense constructs, and naturally produced hairpins -

miRNAs

Module 04: Animal miRNA biogenesis

Cell Signalling Biology - Michael J. Berridge - www.cellsignallingbiology.org - 2012

Animal miRNA Function - Overview

The task of establishing microRNA properties and function of individual miRs is ongoing and already there are indications that each miR can modulate the activity of up to 100 mRNAs to influence a large number of key biological processes:

• Maintenance of embryonic stem (ES) cell pluripotency.• MicroRNA modulation of cell-cycle regulatory mechanisms• p53 functions and microRNAs• MicroRNA regulation of differentiation

• Differentiation of cardiac cells• Differentiation of smooth muscle cells

• Cell proliferation• Apoptosis• Stress responses.• MicroRNA dysregulation and cancer

Module 11: Cell Proliferation

siRNAs

• Short (small) Interfering RNAs – siRNAs• NOT miRNAs, produced by different pathways, have different functions• ARE dsRNA-produced, are non-coding RNAs with regulatory functions

• PTGS• TGS• epigenetics

• Usually does not involve hairpin• Usually does involve an RNA-dependent RNA polymerase• May be cut by same RNAse III type proteins, but may be isoforms with miRNA

cutters• Load into RISC complexes

siRNAs

• Animals• piRNAs – Piwi-interacting siRNAs• endo-siRNAs

• Plant • Repeat-associated siRNA – ra-siRNA• Trans-acting siRNA – ta-siRNA• Phased secondary – siRNA – pha-siRNA• cis natural antisense siRNA - cis-NAT-siRNA• trans natural antisense siRNA - trans-NAT-siRNA

Module 11: miRNA Function – Embryonic Stem Cell miRNA