title: Search for microRNAs expressed by intracellular bacterial pathogens in infected mammalian cells.
abstract: MicroRNAs are expressed by all multicellular organisms and play a critical role as post-transcriptional regulators of gene expression. Moreover, different microRNA species are known to influence the progression of a range of different diseases, including cancer and microbial infections. A number of different human viruses also encode microRNAs that can attenuate cellular innate immune responses and promote viral replication, and a fungal pathogen that infects plants has recently been shown to express microRNAs in infected cells that repress host cell immune responses and promote fungal pathogenesis. Here, we have used deep sequencing of total expressed small RNAs, as well as small RNAs associated with the cellular RNA-induced silencing complex RISC, to search for microRNAs that are potentially expressed by intracellular bacterial pathogens and translocated into infected animal cells. In the case of Legionella and Chlamydia and the two mycobacterial species M. smegmatis and M. tuberculosis, we failed to detect any bacterial small RNAs that had the characteristics expected for authentic microRNAs, although large numbers of small RNAs of bacterial origin could be recovered. However, a third mycobacterial species, M. marinum, did express an ∼ 23-nt small RNA that was bound by RISC and derived from an RNA stem-loop with the characteristics expected for a pre-microRNA. While intracellular expression of this candidate bacterial microRNA was too low to effectively repress target mRNA species in infected cultured cells in vitro, artificial overexpression of this potential bacterial pre-microRNA did result in the efficient repression of a target mRNA. This bacterial small RNA therefore represents the first candidate microRNA of bacterial origin.
authors.affiliation: Department of Molecular Genetics & Microbiology, Duke University Medical Center, Durham, North Carolina, United States of America.
authors.forename: Yuki
authors.initials: Y
authors.lastname: Furuse
authors.affiliation: Department of Molecular Genetics & Microbiology, Duke University Medical Center, Durham, North Carolina, United States of America.
authors.forename: Ryan
authors.initials: R
authors.lastname: Finethy
authors.affiliation: Department of Molecular Genetics & Microbiology, Duke University Medical Center, Durham, North Carolina, United States of America.
authors.forename: Hector A
authors.initials: HA
authors.lastname: Saka
authors.affiliation: Department of Molecular Genetics & Microbiology, Duke University Medical Center, Durham, North Carolina, United States of America.
authors.forename: Ana M
authors.initials: AM
authors.lastname: Xet-Mull
authors.affiliation: Department of Molecular Genetics & Microbiology, Duke University Medical Center, Durham, North Carolina, United States of America.
authors.forename: Dana M
authors.initials: DM
authors.lastname: Sisk
authors.affiliation: Department of Molecular Genetics & Microbiology, Duke University Medical Center, Durham, North Carolina, United States of America.
authors.forename: Kristen L Jurcic
authors.initials: KL
authors.lastname: Smith
authors.affiliation: Department of Molecular Genetics & Microbiology, Duke University Medical Center, Durham, North Carolina, United States of America.
authors.forename: Sunhee
authors.initials: S
authors.lastname: Lee
authors.affiliation: Department of Molecular Genetics & Microbiology, Duke University Medical Center, Durham, North Carolina, United States of America.
authors.forename: Jörn
authors.initials: J
authors.lastname: Coers
authors.affiliation: Department of Molecular Genetics & Microbiology, Duke University Medical Center, Durham, North Carolina, United States of America.
authors.forename: Raphael H
authors.initials: RH
authors.lastname: Valdivia
authors.affiliation: Department of Molecular Genetics & Microbiology, Duke University Medical Center, Durham, North Carolina, United States of America.
authors.forename: David M
authors.initials: DM
authors.lastname: Tobin
authors.affiliation: Department of Molecular Genetics & Microbiology, Duke University Medical Center, Durham, North Carolina, United States of America.
authors.forename: Bryan R
authors.initials: BR
authors.lastname: Cullen
mesh_terms: D002268:Carboxypeptidases / Q000235:genetics*; D002689:Chlamydia / Q000235:genetics / Q000302:isolation & purification; D005786:Gene Expression Regulation; D059014:High-Throughput Nucleotide Sequencing; D054884:Host-Pathogen Interactions; D006801:Humans; D007113:Immunity, Innate / Q000235:genetics*; D007875:Legionella / Q000235:genetics / Q000302:isolation & purification; D035683:MicroRNAs / Q000235:genetics / Q000302:isolation & purification*; D009169:Mycobacterium tuberculosis / Q000235:genetics / Q000302:isolation & purification; D012329:RNA, Bacterial / Q000235:genetics / Q000302:isolation & purification
chemical_list: D035683:MicroRNAs; D012329:RNA, Bacterial; D002268:Carboxypeptidases; C436327:SCPEP1 protein, human