title: Knockdown of selenocysteine-specific elongation factor in Amblyomma maculatum alters the pathogen burden of Rickettsia parkeri with epigenetic control by the Sin3 histone deacetylase corepressor complex.
abstract: Selenocysteine is the 21st naturally-occurring amino acid. Selenoproteins have diverse functions and many remain uncharacterized, but they are typically associated with antioxidant activity. The incorporation of selenocysteine into the nascent polypeptide chain recodes the TGA stop codon and this process depends upon a number of essential factors including the selenocysteine elongation factor (SEF). The transcriptional expression of SEF did not change significantly in tick midguts throughout the blood meal, but decreased in salivary glands to 20% at the end of the fast feeding phase. Since selenoprotein translation requires this specialized elongation factor, we targeted this gene for knockdown by RNAi to gain a global view of the role selenoproteins play in tick physiology. We found no significant differences in tick engorgement and embryogenesis but detected no antioxidant capacity in tick saliva. The transcriptional profile of selenoproteins in R. parkeri-infected Amblyomma maculatum revealed declined activity of selenoprotein M and catalase and increased activity of selenoprotein O, selenoprotein S, and selenoprotein T. Furthermore, the pathogen burden was significantly altered in SEF-knockdowns. We then determined the global impact of SEF-knockdown by RNA-seq, and mapped huge shifts in secretory gene expression that could be the result of downregulation of the Sin3 histone deacetylase corepressor complex.
authors.affiliation: Department of Biological Sciences, the University of Southern Mississippi, Hattiesburg, Mississippi, United States of America.
authors.forename: Steven W
authors.initials: SW
authors.lastname: Adamson
authors.forename: Rebecca E
authors.initials: RE
authors.lastname: Browning
authors.forename: Khemraj
authors.initials: K
authors.lastname: Budachetri
authors.forename: José M C
authors.initials: JM
authors.lastname: Ribeiro
authors.forename: Shahid
authors.initials: S
authors.lastname: Karim
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D044127:Epigenesis, Genetic; D005786:Gene Expression Regulation; D055785:Gene Knockdown Techniques; D026863:Ixodidae / Q000382:microbiology*; D008969:Molecular Sequence Data; D010445:Peptide Elongation Factors / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism; D010802:Phylogeny; D012281:Rickettsia / Q000235:genetics / Q000302:isolation & purification*; D017279:Selenocysteine / Q000378:metabolism*; D051140:Selenoproteins / Q000235:genetics; D017386:Sequence Homology, Amino Acid; D056264:Sin3 Histone Deacetylase and Corepressor Complex / Q000502:physiology*; D014158:Transcription, Genetic
chemical_list: D010445:Peptide Elongation Factors; D051140:Selenoproteins; D017279:Selenocysteine; D056264:Sin3 Histone Deacetylase and Corepressor Complex