Biosynthesis of catalytically active rat testosterone 5. alpha. -reductase in microinjected Xenopus oocytes: Evidence for tissue-specific differences in translatable mRNA

Journal Article · Mon Aug 01 04:00:00 EDT 1988 · Proceedings of the National Academy of Sciences of the United States of America; (USA)

DOI:https://doi.org/10.1073/pnas.85.16.5824· OSTI ID:5564988

Farkash, Y; Soreq, H; Orly, J ^[1]

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1. Hebrew Univ. of Jerusalem (Israel)

The enzyme 4-ene-3-ketosteroid-5{alpha}-oxidoreductase plays a key role in androgen-dependent target tissues, where it catalyzes the conversion of testosterone to the biologically active dihydrotestosterone. The regulation of 5{alpha}-reductase expression has not been studied at the molecular level as the enzyme is a membrane protein that is labile in cell-free homogenates. The authors developed a sensitive bioassay of the enzyme activity expressed in Xenopus oocytes microinjected with rat liver and prostate mRNA. After microinjection, incubation of intact oocytes in the presence of ({sup 3}H)testosterone revealed the in ovo appearance of active 5{alpha}-reductase. Polyandenylylated RNA was fractionated by sucrose gradient centrifugation, and the enzymatic activity was shown to be encoded by a 1,600- to 2,000-base-pair fraction of hepatic poly(A){sup +} RNA. 5{alpha}-Reductase mRNA was most efficiently translated when up to 80 ng of RNA was injected per oocyte. In the injected oocytes, 5{alpha}-reductase mRNA was found to be a short-lived molecule whereas its in ovo translatable 5{alpha}-reductase protein exhibited stable enzymatic activity for over 40 hr. Moreover, the levels of translatable tissue-specific 5{alpha}-reductase mRNAs as monitored in the Xenopus oocytes correlated with the variable 5{alpha}-reductase activities in female rat liver, male rat liver, and prostate homogenates. Altogether, these results provide supporting evidence in favor of the transcriptional control of 5{alpha}-reductase expression in rat tissues.

• OSTI ID: 5564988
• Journal Information: Proceedings of the National Academy of Sciences of the United States of America; (USA), Journal Name: Proceedings of the National Academy of Sciences of the United States of America; (USA) Vol. 85:16; ISSN PNASA; ISSN 0027-8424
• Country of Publication: United States
• Language: English

Related Subjects

550201* -- Biochemistry-- Tracer Techniques
59 BASIC BIOLOGICAL SCIENCES
AMPHIBIANS
ANDROGENS
ANDROSTANES
ANIMALS
AQUATIC ORGANISMS
BIOCHEMICAL REACTION KINETICS
BIOSYNTHESIS
BODY
CENTRIFUGATION
DIGESTIVE SYSTEM
ENZYME ACTIVITY
ENZYMES
GERM CELLS
GLANDS
HORMONES
HYDROGEN COMPOUNDS
HYDROXY COMPOUNDS
KETONES
KINETICS
LIVER
MALE GENITALS
MESSENGER-RNA
NUCLEIC ACIDS
OOCYTES
ORGANIC COMPOUNDS
ORGANS
OXIDOREDUCTASES
PROSTATE
REACTION KINETICS
RNA
SEPARATION PROCESSES
STEROID HORMONES
STEROIDS
SYNTHESIS
TESTOSTERONE
TRANSCRIPTION
TRITIUM COMPOUNDS
VERTEBRATES