Nominal growth hormone pulses in otherwise normal masculine plasma profiles induce intron retention of overexpressed hepatic CYP2C11 with associated nuclear splicing deficiency.
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.
Pampori
N A
NA
Laboratories of Biochemistry, University of Pennsylvania School of Veterinary Medicine, Philadelphia 19104-6048, USA.
Shapiro
B H
BH
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
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