# Comparative analysis of alkyne- and desthiobiotinylated photoaffinity probes for chemotranscriptomic profiling

## TL;DR

This paper compares two types of photoaffinity probes for studying small molecule-RNA interactions and finds that one causes too many false positives.

## Contribution

The study evaluates desthiobiotinylated probes as an alternative to alkyne-modified probes for chemotranscriptomic profiling.

## Key findings

- Both alkyne and desthiobiotin probes bind to the FMN riboswitch target.
- Desthiobiotin shows high non-specific RNA interactions in dot blots and RT-qPCR.
- Transcriptome-wide sequencing confirms the lack of selectivity in desthiobiotin.

## Abstract

Understanding small molecule–RNA interactions is a crucial part in drug development and fundamental biology. Chemotranscriptomic profiling is emerging as a powerful platform to interrogate interactions of small molecules with entire transcriptomes. This technique relies on photoaffinity probes that covalently capture small molecule RNA interactions. Most photoaffinity probes bear an alkyne handle that requires additional inefficient functionalization and purification steps after RNA capture. We sought to improve the workflow by directly desthiobiotinylating a photoaffinity probe, omitting these additional alkyne functionalization steps. Here, we compare the suitability of desthiobiotin and alkyne modified Ribocil-derived photoaffinity probes for chemotranscriptomic profiling. Our results demonstrate binding of both photoaffinity probes to their specific target, the FMN riboswitch, using in vitro transcription/translation and RT-qPCR. We also observed high unspecific interactions due to proposed weak and non-specific binding of the desthiobiotin moiety to RNA analyzed by dot blots and RT-qPCR. Finally, transcriptome-wide sequencing confirmed the unselective interaction of desthiobiotin. These findings suggest that desthiobiotin is an inefficient enrichment handle for the design of photoaffinity probes, resulting in many off-target interactions.

The suitability of desthiobiotin and alkyne modified Ribocil photoaffinity probes for chemotranscriptomic profiling were compared. Desthiobiotin appears to unselectively interact with RNA, rendering it unfavorable for transcriptome-wide studies.