title: Nominal growth hormone pulses in otherwise normal masculine plasma profiles induce intron retention of overexpressed hepatic CYP2C11 with associated nuclear splicing deficiency.
abstract: Restoration of circulating masculine GH profiles at minipulse amplitudes (i.e. approximately 10% of normal) to hypophysectomized male rats and neonatal administration of monosodium glutamate (MSG), producing a similar plasma GH profile, both result in an overexpression (approximately 200-300%) of CYP2C11 messenger RNA (mRNA), the predominant hepatic cytochrome P450 (CYP) drug-metabolizing enzyme in adult male rats. Coincident with the severalfold elevation in transcript level is a modest 10-30% overexpression of CYP2C11 protein and its catalytic activities. Using hepatic tissue from adult, neonatally MSG-treated rats, we have cloned a variant species of CYP2C11 mRNA containing all of the essential elements of a full-length complementary DNA, including initiating codon, termination codon, and polyadenylase tail. In addition, the transcript contains a 742-bp intervening sequence (identical to the complete terminal intron) between the last and penultimate exons, and an intron-specific oligo probe for Northern blotting demonstrates the presence of the variant transcript in liver of MSG-treated rats. Associated with the overexpression and intron retention of the transcript is a 50% reduction in the nuclear splicing capacity of the liver for model precursor CYP2C11 mRNA. It is proposed that this splicing defect may be a consequence of the mini-GH pulses (secreted in otherwise normal masculine plasma profiles) signaling abnormal processing of precursor CYP2C11 mRNA to produce a substantial portion of intron retained, nontranslatable transcript.
authors.affiliation: Laboratories of Biochemistry, University of Pennsylvania School of Veterinary Medicine, Philadelphia 19104-6048, USA.
authors.forename: N A
authors.initials: NA
authors.lastname: Pampori
authors.forename: B H
authors.initials: BH
authors.lastname: Shapiro
mesh_terms: D000818:Animals; D000831:Animals, Newborn; D001189:Aryl Hydrocarbon Hydroxylases; D001483:Base Sequence; D002467:Cell Nucleus / Q000378:metabolism*; D003577:Cytochrome P-450 Enzyme System / Q000235:genetics* / Q000378:metabolism; D000072467:Cytochrome P450 Family 2; D018076:DNA, Complementary / Q000737:chemistry; D005260:Female; D015870:Gene Expression; D013006:Growth Hormone / Q000008:administration & dosage* / Q000097:blood; D007016:Hypophysectomy; D007438:Introns; D008099:Liver / Q000187:drug effects / Q000201:enzymology / Q000648:ultrastructure; D008297:Male; D008969:Molecular Sequence Data; D012326:RNA Splicing; D012333:RNA, Messenger / Q000032:analysis; D051381:Rats; D017207:Rats, Sprague-Dawley; D020133:Reverse Transcriptase Polymerase Chain Reaction; D012727:Sex Characteristics; D012970:Sodium Glutamate / Q000008:administration & dosage; D039181:Steroid 16-alpha-Hydroxylase; D013250:Steroid Hydroxylases / Q000235:genetics* / Q000378:metabolism
chemical_list: D018076:DNA, Complementary; D012333:RNA, Messenger; D013006:Growth Hormone; D003577:Cytochrome P-450 Enzyme System; D013250:Steroid Hydroxylases; D001189:Aryl Hydrocarbon Hydroxylases; C450279:CYP2C11 protein, rat; D000072467:Cytochrome P450 Family 2; D039181:Steroid 16-alpha-Hydroxylase; D012970:Sodium Glutamate