RppH can faithfully replace TAP to allow cloning of 5′-triphosphate carrying small RNAs

Abstract

RNA interference was first described in the nematode Caenorhabditis elegans. Ever since, several new endogenous small RNA pathways have been described and characterized to different degrees. The very prominent secondary small interfering RNAs, also called 22G-RNAs, bear a 5′ triphosphate group after loading into an Argonaute protein. This creates a technical issue, since 5′PPP groups decrease cloning efficiency for small RNA sequencing. To increase cloning efficiency of these small RNA species, a common practice in the field is the treatment of RNA samples, prior to library preparation, with Tobacco Acid pyrophosphatase (TAP). Recently, TAP production and supply was discontinued, so an alternative must be devised. We turned to RNA 5′ pyrophosphohydrolase (RppH), a commercially available pyrophosphatase isolated from E. coli. Here we directly compare TAP and RppH in their use for small RNA library preparation. We show that RppH-treated samples faithfully recapitulate TAP-treated samples. Specifically, there is enrichment for 22G-RNAs and mapped small RNA reads show no small RNA transcriptome-wide differences between RppH and TAP treatment. We propose that RppH can be used as a small RNA pyrophosphatase to enrich for triphosphorylated small RNA species and show that RppH- and TAP-derived datasets can be used in direct comparison.

• We show that treatment of small RNA samples with RppH prior to sequencing library preparation increases the cloning efficiency of 5′ triphosphorylated small RNAs;

• RppH treatment is a valid alternative to TAP treatment.