02206nas a2200373   4500000000100000000000100001008003900002260001700041653001800058653001400076653002700090653002000117653001300137653002200150653001600172653002200188100002000210700001700230700001900247700002300266700002000289700002000309700001800329700001900347700001800366700002100384700002900405245005500434856008400489300001300573490000700586520122500593022001401818       0                             d  cNov 20, 202510aAntisense RNA10aConsortia10aGastrointestinal tract10aGene expression10aShigella10aShigella flexneri10aShigellosis10aVirulence Factors1 aThibault Frisch1 aPetra Geiser1 aMargarita Komi1 aPhilip A. Karlsson1 aAnjeela Bhetwal1 aLaura Jenniches1 aLars Barquist1 aErik Holmqvist1 aAndré Mateus1 aMikael E. Sellin1 aMaria Letizia Di Martino00aThe pcnB gene sustains Shigella flexneri virulence  uhttps://journals.plos.org/plospathogens/article?id=10.1371/journal.ppat.1013727  ae10137270 v213 aThe enteropathogen Shigella flexneri employs a Type Three Secretion System (T3SS) to colonize intestinal epithelial cells. Genes encoding the T3SS are located on a large IncFII virulence plasmid, pINV. T3SS expression comes at the expense of slowed Shigella growth and is therefore strictly controlled by both transcriptional and post-transcriptional mechanisms. Following up on a recent genome-wide screen, we here show that the chromosomal gene pcnB, encoding the poly-A polymerase I (PAP-I), slows Shigella growth at 37°C, while it at the same time promotes early colonization of a human epithelial enteroid model. Proteomic profiling revealed that pcnB drives global increase of the Shigella T3SS virulence program. Accordingly, pcnB upholds pINV replication to a level favourable for Shigella virulence. This is achieved through increased degradation of the antisense RNA CopA, involved in plasmid replication control. The pcnB effect on pINV replication was found to also ensure longer-term intraepithelial expansion of Shigella following human intestinal epithelium invasion. Our findings exemplify how an adequate pINV level, sustained by pcnB, underpins the successful execution of Shigella´s infection cycle.  a1553-7374