title: Polyamine-regulated unproductive splicing and translation of spermidine/spermine N1-acetyltransferase.
abstract: Spermidine/spermine N1-acetyltransferase (SSAT), the rate-controlling enzyme in the interconversion of spermidine and spermine, is regulated by polyamines and their analogs at many levels of gene expression. Recently, SSAT pre-mRNA has been shown to undergo alternative splicing by inclusion of an exon that contains premature termination codons. In the present study, we show that alterations in the intracellular polyamine level resulted in a change in the relative abundance of SSAT transcripts. Addition of polyamines or their N-diethylated analogs reduced the amount of the variant transcript, whereas polyamine depletion by 2-difluoromethylornithine or MG-132 enhanced the exon inclusion. Experiments performed with protein synthesis inhibitors and siRNA-mediated down-regulation of Upf1 protein verified that the variant transcript was degraded by nonsense-mediated mRNA decay (NMD). Interestingly, several proteins have been shown to regulate their expression by alternative splicing-coupled NMD, termed regulated unproductive splicing and translation (RUST). Our present results suggest that in the case of SSAT, RUST is mediated by polyamines, and this system functions to fine-tune the polyamine metabolism.
authors.affiliation: Department of Biotechnology and Molecular Medicine, A.I. Virtanen Institute for Molecular Sciences, University of Kuopio, Kuopio, finland. Mervi.Hyvonen@uku.fi
authors.forename: Mervi T
authors.initials: MT
authors.lastname: Hyvönen
authors.forename: Anne
authors.initials: A
authors.lastname: Uimari
authors.forename: Tuomo A
authors.initials: TA
authors.lastname: Keinänen
authors.forename: Sami
authors.initials: S
authors.lastname: Heikkinen
authors.forename: Riikka
authors.initials: R
authors.lastname: Pellinen
authors.forename: Tiina
authors.initials: T
authors.lastname: Wahlfors
authors.forename: Arja
authors.initials: A
authors.lastname: Korhonen
authors.forename: Ale
authors.initials: A
authors.lastname: Närvänen
authors.forename: Jarmo
authors.initials: J
authors.lastname: Wahlfors
authors.forename: Leena
authors.initials: L
authors.lastname: Alhonen
authors.forename: Juhani
authors.initials: J
authors.lastname: Jänne
mesh_terms: D000123:Acetyltransferases / Q000235:genetics / Q000378:metabolism*; D017398:Alternative Splicing; D000818:Animals; D005091:Exons; D005260:Female; D015971:Gene Expression Regulation, Enzymologic / Q000187:drug effects*; D051379:Mice; D008822:Mice, Transgenic; D011247:Pregnancy; D014176:Protein Biosynthesis; D011500:Protein Synthesis Inhibitors / Q000494:pharmacology; D012322:RNA Precursors / Q000378:metabolism; D012333:RNA, Messenger / Q000378:metabolism; D034741:RNA, Small Interfering / Q000378:metabolism; D013095:Spermidine / Q000494:pharmacology*; D013096:Spermine / Q000031:analogs & derivatives / Q000494:pharmacology*
chemical_list: D011500:Protein Synthesis Inhibitors; D012322:RNA Precursors; D012333:RNA, Messenger; D034741:RNA, Small Interfering; D013096:Spermine; D000123:Acetyltransferases; D013095:Spermidine