The glucocorticoid receptor is a ubiquitous transcription factor mediating adaptation to environmental challenges and stress. Selective Nr3c1 (the glucocorticoid receptor gene) ablation in mouse dopaminoceptive neurons expressing dopamine receptor 1a, but not in dopamine-releasing neurons, markedly decreased the motivation of mice to self-administer cocaine, dopamine cell firing and the control exerted by dopaminoceptive neurons on dopamine cell firing activity. In contrast, anxiety was unaffected, indicating that glucocorticoid receptors modify a number of behavioral disorders through different neuronal populations.
At the termination step of protein synthesis, hydrolysis of the peptidyl-tRNA is jointly catalysed at the ribosome by the termination codon and the polypeptide release factor (eRF1 in eukaryotes). eRF1 forms in vivo and in vitro a stable complex with release factor eRF3, an eRF1-dependent and ribosomedependent GTPase. The role of the eRF1ceRF3 complex in translation remains unclear. We have undertaken a systematic analysis of the interactions between the human eRF1 and eRF3 employing a yeast two-hybrid assay. We show that the Nterminal parts of eRF1 (positions 1^280) and of eRF3 (positions 1^477) are either not involved or non-essential for binding. Two regions in each factor are critical for mutual binding: positions 478^530 and 628^637 of eRF3 and positions 281^305 and 4114 15 of eRF1. The GTP binding domain of eRF3 is not involved in complex formation with eRF1. The GILRY pentamer (positions 411^415) conserved in eukaryotes and archaebacteria is critical for eRF1's ability to stimulate eRF3 GTPase. The human eRF1 lacking 22 C-terminal amino acids remains active as a release factor and promotes an eRF3 GTPase activity whereas Cterminally truncated eRF3 is inactive as a GTPase.z 1999 Federation of European Biochemical Societies.
The glycolytic enzyme enolase (EC 4.2.1.11) is active as dimers formed from three subunits encoded by different genes. The embryonic αα isoform remains distributed in many adult cell types, whereas a transition towards ββ and γγ isoforms occurs in striated muscle cells and neurons respectively. It is not understood why enolase exhibits tissue-specific isoforms with very close functional properties. We approached this problem by the purification of native ββ-enolase from mouse hindlimb muscles and by raising specific antibodies of high titre against this protein. These reagents have been useful in revealing a heterogeneity of the β-enolase subunit that changes with in i o and in itro maturation. A basic carboxypeptidase appears to be involved in generating an acidic β-enolase variant, and may regulate plasminogen binding by this subunit. We show for the
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