Hormonal regulation of gluconeogenic gene transcription in the liver

Glucose homeostasis in mammals is achieved by the actions of counterregulatory hormones, namely insulin, glucagon and glucocorticoids. Glucose levels in the circulation are regulated by the liver, the metabolic centre which produces glucose when it is scarce in the blood. This process is catalysed by two rate-limiting enzymes, phosphoenolpyruvate carboxykinase (PEPCK) and glucose-6-phosphatase (G6Pase) whose gene expression is regulated by hormones. Hormone response units (HRUs) present in the two genes integrate signals from various signalling pathways triggered by hormones. How such domains are arranged in the regulatory region of these two genes, how this complex regulation is accomplished and the latest advancements in the field are discussed in this review.     

Incorporation of single nucleoside triphosphates by isolated cell nuclei

Manganese ions can form insoluble complexes or coprecipitates with nucleoside triphosphates at high pH. We have demonstrated that nucleoside triphosphates found in precipitated complexes exhibit properties similar to those of poliribo-nucleotides in all steps of the Schmidt-Tannhausers procedure: insoluble in perchloric acid, trichloroacetic acid, and ethanol and soluble in 0.2 n NaOH. These observations could be applied to experimentation on RNA synthesis from nucleoside triphosphates.     

A comparison of nucleoside (beta-S)triphosphates and nucleoside (gamma-S)triphosphates as suitable substrates for measuring transcription initiation in preparations of cell nuclei

RNA chains initiated with nucleoside (beta-S)triphosphates and (gamma-S)triphosphates retain the thiol groups and can be separated from thiol-free RNA by chromatography on mercury-Sepharose. Thiol-containing mouse mammary tumor virus (MMTV) RNA synthesized by preparations of nuclei from virus-infected cells was quantitated by nucleic acid filter hybridization. With ATP beta S and GTP beta S, region-specific initiation of MMTV RNA chains was detected in the cell free system. However, with ATP gamma S and GTP gamma S, region-specific initiation was not clearly demonstrable. The nuclear preparations can also transfer thiol groups, presumably in the form of thiophosphate, from ATP gamma S or GTP gamma S onto preexisting RNA molecules; little or no thiol-transfer occurs with the two (beta-S)-analogues. The thiophosphate transfer activity apparently interferes with the measurement of RNA chain initiation with ATP gamma S and GTP gamma S.