Abstract
All mRNA products are currently manufactured in in vitro transcription
(IVT) reactions that utilize single-subunit RNA polymerase (RNAP)
biocatalysts. Although it is known that discrete polymerases exhibit
highly variable bioproduction phenotypes, including different relative
processivity rates and impurity generation profiles, only a handful of
enzymes are generally available for mRNA biosynthesis. This limited RNAP
toolbox restricts strategies to design and troubleshoot new mRNA
manufacturing processes, which is particularly undesirable given the
continuing diversification of mRNA product lines towards larger and more
complex molecules. Herein, we describe development of a high-throughput
RNAP screening platform, comprising complementary in silico and in vitro
testing modules, that enables functional characterisation of large
enzyme libraries. Utilizing this system, we identified eight novel
sequence-diverse RNAPs, with associated active cognate promoters, and
subsequently validated their performance as recombinant enzymes in
IVT-based mRNA production processes. By increasing the number of
available characterized functional RNAPs by > 130% and
providing a platform to rapidly identify further potentially useful
enzymes, this work significantly expands the RNAP biocatalyst solution
space for mRNA manufacture, thereby enhancing capability to achieve
application and molecule-specific optimisation of product yield and
quality.