title: Translational and transcriptional control of Sp1 against ischaemia through a hydrogen peroxide-activated internal ribosomal entry site pathway.
abstract: The exact mechanism underlying increases in Sp1 and the physiological consequences thereafter remains unknown. In rat primary cortical neurons, oxygen-glucose deprivation (OGD) causes an increase in H(2)O(2) as well as Sp1 in early ischaemia but apparently does not change mRNA level or Sp1 stability. We hereby identified a longer 5'-UTR in Sp1 mRNA that contains an internal ribosome entry site (IRES) that regulates rapid and efficient translation of existing mRNAs. By using polysomal fragmentation and bicistronic luciferase assays, we found that H(2)O(2) activates IRES-dependent translation. Thus, H(2)O(2) or tempol, a superoxide dismutase-mimetic, increases Sp1 levels in OGD-treated neurons. Further, early-expressed Sp1 binds to Sp1 promoter to cause a late rise in Sp1 in a feed-forward manner. Short hairpin RNA against Sp1 exacerbates OGD-induced apoptosis in primary neurons. While Sp1 levels increase in the cortex in a rat model of stroke, inhibition of Sp1 binding leads to enhanced apoptosis and cortical injury. These results demonstrate that neurons can use H(2)O(2) as a signalling molecule to quickly induce Sp1 translation through an IRES-dependent translation pathway that, in cooperation with a late rise in Sp1 via feed-forward transcriptional activation, protects neurons against ischaemic damage.
authors: Department of Pharmacology, Institute of Bioinformatics and Biosignal Transduction, College of Bioscience and Biotechnology, National Cheng-Kung University, Tainan 701, Taiwan.
authors: Shiu Hwa
authors: SH
authors: Yeh
authors: Wen Bin
authors: WB
authors: Yang
authors: Po Wu
authors: PW
authors: Gean
authors: Chung Yi
authors: CY
authors: Hsu
authors: Joseph T
authors: JT
authors: Tseng
authors: Tsung Ping
authors: TP
authors: Su
authors: Wen Chang
authors: WC
authors: Chang
authors: Jan Jong
authors: JJ
authors: Hung
mesh_terms: D020121:5' Untranslated Regions; D000818:Animals; D002545:Brain Ischemia / Q000378:metabolism*; D005947:Glucose / Q000502:physiology; D006801:Humans; D006861:Hydrogen Peroxide / Q000494:pharmacology*; D008297:Male; D009474:Neurons / Q000378:metabolism; D010100:Oxygen / Q000502:physiology; D014176:Protein Biosynthesis; D051381:Rats; D012270:Ribosomes / Q000378:metabolism; D016329:Sp1 Transcription Factor / Q000096:biosynthesis / Q000235:genetics* / Q000378:metabolism; D014158:Transcription, Genetic; D015533:Transcriptional Activation
chemical_list: D020121:5' Untranslated Regions; D016329:Sp1 Transcription Factor; D006861:Hydrogen Peroxide; D005947:Glucose; D010100:Oxygen