title: Production of ACAT1 56-kDa isoform in human cells via trans-splicing involving the ampicillin resistance gene.
abstract: Trans-splicing, a process involving the cleavage and joining of two separate transcripts, can expand the transcriptome and proteome in eukaryotes. Chimeric RNAs generated by trans-splicing are increasingly described in literatures. The widespread presence of antibiotic resistance genes in natural environments and human intestines is becoming an important challenge for public health. Certain antibiotic resistance genes, such as ampicillin resistance gene (Amp(r)), are frequently used in recombinant plasmids. Until now, trans-splicing involving recombinant plasmid-derived exogenous transcripts and endogenous cellular RNAs has not been reported. Acyl-CoA:cholesterol acyltransferase 1 (ACAT1) is a key enzyme involved in cellular cholesterol homeostasis. The 4.3-kb human ACAT1 chimeric mRNA can produce 50-kDa and 56-kDa isoforms with different enzymatic activities. Here, we show that human ACAT1 56-kDa isoform is produced from an mRNA species generated through the trans-splicing of an exogenous transcript encoded by the antisense strand of Amp(r) (asAmp) present in common Amp(r)-plasmids and the 4.3-kb endogenous ACAT1 chimeric mRNA, which is presumably processed through a prior event of interchromosomal trans-splicing. Strikingly, DNA fragments containing the asAmp with an upstream recombined cryptic promoter and the corresponding exogenous asAmp transcripts have been detected in human cells. Our findings shed lights on the mechanism of human ACAT1 56-kDa isoform production, reveal an exogenous-endogenous trans-splicing system, in which recombinant plasmid-derived exogenous transcripts are linked with endogenous cellular RNAs in human cells, and suggest that exogenous DNA might affect human gene expression at both DNA and RNA levels.
authors.affiliation: State Key Laboratory of Molecular Biology, Institute of Biochemistry and Cell Biology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai 200031, China.
authors.forename: Guang-Jing
authors.initials: GJ
authors.lastname: Hu
authors.forename: Jia
authors.initials: J
authors.lastname: Chen
authors.forename: Xiao-Nan
authors.initials: XN
authors.lastname: Zhao
authors.forename: Jia-Jia
authors.initials: JJ
authors.lastname: Xu
authors.forename: Dong-Qing
authors.initials: DQ
authors.lastname: Guo
authors.forename: Ming
authors.initials: M
authors.lastname: Lu
authors.forename: Ming
authors.initials: M
authors.lastname: Zhu
authors.forename: Ying
authors.initials: Y
authors.lastname: Xiong
authors.forename: Qin
authors.initials: Q
authors.lastname: Li
authors.forename: Catherine Cy
authors.initials: CC
authors.lastname: Chang
authors.forename: Bao-Liang
authors.initials: BL
authors.lastname: Song
authors.forename: Ta-Yuan
authors.initials: TY
authors.lastname: Chang
authors.forename: Bo-Liang
authors.initials: BL
authors.lastname: Li
mesh_terms: D000101:Acetyl-CoA C-Acetyltransferase / Q000145:classification / Q000235:genetics / Q000378:metabolism*; D000668:Ampicillin Resistance / Q000235:genetics; D001483:Base Sequence; D002460:Cell Line; D057809:HEK293 Cells; D006801:Humans; D008969:Molecular Sequence Data; D010957:Plasmids / Q000235:genetics / Q000378:metabolism; D011401:Promoter Regions, Genetic; D020033:Protein Isoforms / Q000145:classification / Q000235:genetics / Q000378:metabolism; D012333:RNA, Messenger / Q000378:metabolism; D017422:Sequence Analysis, DNA; D020040:Trans-Splicing
chemical_list: D020033:Protein Isoforms; D012333:RNA, Messenger; C506639:ACAT1 protein, human; D000101:Acetyl-CoA C-Acetyltransferase