What Was the Set of Ubiquitin and Ubiquitin-Like Conjugating Enzymes in the Eukaryote Common Ancestor?

Ubiquitin (Ub)-conjugating enzymes (E2) are key enzymes in ubiquitination or Ub-like modifications of proteins. We searched for all proteins belonging to the E2 enzyme super-family in seven species (Homo sapiens, Mus musculus, Drosophila melanogaster, Caenorhabditis elegans, Schizosaccharomyces pombe, Saccharomyces cerevisiae, and Arabidopsis thaliana) to identify families and to reconstruct each family’s phylogeny. Our phylogenetic analysis of 207 genes led us to define 17 E2 families, with 37 E2 genes, in the human genome. The subdivision of E2 into four classes did not correspond to the phylogenetic tree. The sequence signature HPN (histidine–proline–asparagine), followed by a tryptophan residue at 16 (up to 29) amino acids, was highly conserved. When present, the active cysteine was found 7 to 8 amino acids from the C-terminal end of HPN. The secondary structures were characterized by a canonical alpha/beta fold. Only family 10 deviated from the common organization because the proteins were devoid of enzymatic activity. Family 7 had an insertion between beta strands 1 and 2; families 3, 5 and 14 had an insertion between the active cysteine and the conserved tryptophan. The three-dimensional data of these proteins highlight a strong structural conservation of the core domain. Our analysis shows that the primitive eukaryote ancestor possessed a diversified set of E2 enzymes, thus emphasizing the importance of the Ub pathway. This comprehensive overview of E2 enzymes emphasizes the diversity and evolution of this superfamily and helps clarify the nomenclature and true orthologies. A better understanding of the functions of these enzymes is necessary to decipher several human diseases

Ani Litan (right) and another actor in a scene from a VYKT (Warsaw Yiddish Art Theater) performance of Shulamis by Abraham Goldfaden, , Lwów, Poland (now L'viv, Ukraine)

Digital imagedigitize

DAX-1 Blocks Steroid Production at Multiple Levels 1

International audienceDAX-1 is an unusual member of the nuclear hormone receptor superfamily whose expression is mainly, but not uniquely, restricted to steroidogenic tissues. We have recently shown that DAX-1 can block the first and rate-limiting step in steroid biosynthesis by repressing StAR (steroidogenic acute regulatory protein) expression. Here we show that DAX-1 blocks steroid production at multiple levels in the Y-1 mouse adrenocortical tumor cell line. Expression of DAX-1 in Y-1 cells significantly impairs both basal and cAMP-stimulated steroid production, without affecting the functionality of the cAMP-responsive PKA pathway. Experiments using an hydroxylated cholesterol derivative show that biochemical steps in steroidogenesis subsequent to cholesterol delivery to mitochondria are also impaired in Y-1 cells expressing DAX-1. This is explained by the repression of P450scc and 3beta-HSD expression, in addition to StAR. DAX-1 expression in Y-1 cells results in the inhibition of the activity of the StAR, P450scc and 3beta-HSD promoters. An inappropriate steroidogenic block in the male fetus might have an important role in the pathogenesis of sex reversal syndromes caused by a duplication of the genomic region of the X chromosome containing the DAX-1 gene

Demonstration of renin activity in purified rat Leydig cells: evidence for the existence of an endogenous inactive (latent) form of enzyme.

Previous histochemical studies demonstrated the specific localization of immunoreactive renin-like substance in Leydig cells of rat testes. The studies reported herein demonstrate a specific renin enzyme activity in the two purified populations of Leydig cells (I and II) of mature rat testes. Leydig cells of both populations also exhibited an inactive (latent) renin which was activated by the sulfhydryl reagents dithiothreitol, beta-mercaptoethanol, glutathione, and cysteine but not by limited proteolysis by trypsin, which is a characteristic activating agent for prorenin or inactive renin of the zymogen type. The activation of latent renin by dithiothreitol produced approximately 5-and 10-fold increases in renin activity in Leydig cell populations I and II, respectively. Active and latent renin showed strong affinity to an antirat renin immunoglobulin-Sepharose column, indicating a close immunological relationship of latent renin to active renin. Both active and latent renin from Leydig cell populations (I and II) exhibited the pH optimum of 6.0. The gel filtration of Leydig cell extracts characteristically revealed that the apparent mol wts of active and latent renin were 39,000 and 48,000, respectively. Both active and latent renin in Leydig cells remained almost at similar levels through four continuous subcultures. The activity of latent renin slightly increased during the four consecutive subcultures, while active renin levels remained almost constant.Journal ArticleResearch Support, U.S. Gov't, P.H.S.SCOPUS: ar.jinfo:eu-repo/semantics/publishe