title: The optional long 5'-untranslated region of human ACAT1 mRNAs impairs the production of ACAT1 protein by promoting its mRNA decay.
abstract: We have previously reported that human ACAT1 mRNAs produce the 50 kDa protein using the AUG(11397-1399) initiation codon, and also a minor 56 kDa isoform using the upstream in-frame GGC(1274-1276) initiation codon. The GGC(1274-1276) codon is located at the optional long 5'-untranslated region (5'-UTR, nt 1-1396) of the mRNAs. The DNA sequences corresponding to this 5'-UTR are located in two different chromosomes, 7 and 1. In the current work, we report that the optional long 5'-UTR significantly impairs the production of human ACAT1 protein initiated from the AUG(1397-1399)codon, mainly by promoting its mRNA decay. The western blot analyses indicated that the optional long 5'-UTR potently impaired the production of different proteins initiated from the AUG(1397-1399) codon, meaning that this impairing effect was not influenced by the 3'-UTR or the coding sequence of ACAT1 mRNA. The results of reverse transcription-quantitative polymerase chain reaction demonstrated that this 5'- UTR dramatically reduced the contents of its linked mRNAs. Analyses of the protein to mRNA ratios showed that this 5'-UTR mainly decreased its mRNA stability rather than altering its translational efficiency. We next performed the plasmid transfection experiments and used actinomycin D to inhibit transcription. The results showed that this 5'-UTR promoted its mRNA decay. Additional transfection and nucleofection experiments using RNAs prepared in vitro illustrated that, in both the cytoplasm and the nucleus of cells, the optional long 5'-UTR-linked mRNAs decayed faster than those without the link. Overall, our study brings new insight to the regulation of the human ACAT1 gene expression at the post-transcription level.
authors.affiliation: State Key Laboratory of Molecular Biology, Institute of Biochemistry and Cell Biology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai, China.
authors.forename: Xiaonan
authors.initials: X
authors.lastname: Zhao
authors.forename: Jia
authors.initials: J
authors.lastname: Chen
authors.forename: Lei
authors.initials: L
authors.lastname: Lei
authors.forename: Guangjing
authors.initials: G
authors.lastname: Hu
authors.forename: Ying
authors.initials: Y
authors.lastname: Xiong
authors.forename: Jiajia
authors.initials: J
authors.lastname: Xu
authors.forename: Qin
authors.initials: Q
authors.lastname: Li
authors.forename: Xinying
authors.initials: X
authors.lastname: Yang
authors.forename: Catherine Cy
authors.initials: CC
authors.lastname: Chang
authors.forename: Baoliang
authors.initials: B
authors.lastname: Song
authors.forename: Tayuan
authors.initials: T
authors.lastname: Chang
authors.forename: Boliang
authors.initials: B
authors.lastname: Li
mesh_terms: D020121:5' Untranslated Regions; D000818:Animals; D001483:Base Sequence; D015153:Blotting, Western; D016466:CHO Cells; D003062:Codon; D006224:Cricetinae; D003412:Cricetulus; D017931:DNA Primers; D006801:Humans; D009690:Nucleic Acid Conformation; D012333:RNA, Messenger / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D002785:Sterol O-Acyltransferase / Q000096:biosynthesis / Q000235:genetics / Q000502:physiology*
chemical_list: D020121:5' Untranslated Regions; D003062:Codon; D017931:DNA Primers; D012333:RNA, Messenger; D002785:Sterol O-Acyltransferase; C493492:sterol O-acyltransferase 1