Recruitment of a repressosome complex at the growth hormone receptor promoter and its potential role in diabetic nephropathy.

The growth hormone (GH)-GH receptor (GHR) axis modulates growth and metabolism and contributes to complications of diabetes mellitus. We analyzed the promoter region of the dominant transcript (L2) of the murine GHR to determine that a cis element, L2C1, interacts with transcription factors NF-Y, BTEB1, and HMG-Y/I. These proteins individually repress GHR expression and together form a repressosome complex in conjunction with mSin3b. The histone deacetylase inhibitor trichostatin A increases expression of the murine GHR gene, enhances association of acetyl-H3 at L2C1, inhibits formation of the repressosome complex, and decreases NF-Y's association with L2C1. Our studies reveal that murine models of experimental diabetes mellitus are characterized by reduced hepatic GHR expression, decreased acetyl-H3 associated with L2C1, and increased formation of the repressosome complex. In contrast, in the kidney diabetes mellitus is associated with enhanced GHR expression and lack of alteration in the assembly of the repressosome complex, thus permitting exposure of kidneys to the effects of elevated levels of GH in diabetes mellitus. Our findings define a higher-order repressosome complex whose formation correlates with the acetylation status of chromatin histone proteins. The delineation of the role of this repressosome complex in regulating tissue-specific expression of GHR in diabetes mellitus provides a molecular model for the role of GH in the genesis of certain microvascular complications of diabetes mellitus.

PRL, placental lactogen, and GH induce NA(+)/taurocholate-cotransporting polypeptide gene expression by activating signal transducer and activator of transcription-5 in liver cells.

We investigated the transcriptional regulation of the Na(+)/taurocholate cotransporting polypeptide gene by PRL, placental lactogen, and GH. In primary hepatocytes, ovine PRL induced a dose-dependent phosphorylation and nuclear translocation of signal transducers and activators of transcription-5a and -5b, but not -1 or -3, whereas mouse placental lactogen I and rat GH activated -5a, -5b, and -1. In EMSAs, ovine PRL, mouse placental lactogen I, and rat GH increased the specific DNA binding of nuclear signal transducer and activator of transcription-5 to its consensus element in both transfected HepG2 cells and primary hepatocytes. PRL, placental lactogen I, and GH also increased Na(+)/taurocholate cotransporting polypeptide mRNA expression in hepatocytes from control and pregnant (mouse placental lactogen I) rats. Genistein, a phosphotyrosine kinase inhibitor, inhibited PRL-induced signal transducer and activator of transcription-5 activation and Na(+)/taurocholate-cotransporting polypeptide mRNA. In HepG2 cells transiently cotransfected with either the long form of the rat PRL receptor or rat GH receptor, signal transducer and activator of transcription-5a and a -5-responsive luciferase expression vector containing the Na(+)/taurocholate-cotransporting polypeptide promoter, mouse placental lactogen I, like ovine PRL, activated -5a via the long form of the rat PRL receptor; whereas rat GH activated -5a via rat GH receptor, leading to transactivation of the Na(+)/taurocholate-cotransporting polypeptide promoter. These data establish that PRL and placental lactogen I induce Na(+)/taurocholate-cotransporting polypeptide gene expression via signal transducer and activator of transcription-5 proteins in liver, and indicate that these hormones play an important role in regulating liver metabolic function.

Conversion of threonine 757 to valine enhances Stat5a transactivation potential.

The growth hormone family of cytokines transduces intracellular signals through the Jak2-Stat5 pathway to activate the transcription of target genes. Amino acids within the C termini of Stats constitute the transactivation domain but also regulate the time course of tyrosine phosphorylation and extent of DNA binding. We mutated Thr(757) in the C-terminal of Stat5a (Thr-Stat5) to Val (Val-Stat5) and Asp (Asp-Stat5) and examined the effect on nuclear translocation, DNA binding, and prolactin-induced transcriptional activation of a Stat5-responsive luciferase reporter gene. Val-Stat5 produced a 5-fold higher increase in transcriptional activity relative to Thr-Stat5; Asp-Stat5 produced a similar response to Thr-Stat5. The increased transactivation was ligand induced and was not due to differences in basal expression of Val-Stat5 or to a constitutively activated Stat5 protein. Similar rates of loss of DNA binding ability and phosphorylation of Val- and Thr-Stat5 were observed following a single pulse of prolactin, indicating that the dephosphorylation pathways were unaltered. The serine-threonine kinase inhibitor H7 inhibited the transactivation potential of Thr-, Val-, and Asp-Stat5 to a similar extent, eliminating phosphorylation of Thr(757) as a regulatory mechanism. The results suggest that Thr(757) modulates the transactivation potential of Stat5 by a mechanism(s) that is dependent on the formation of Stat5 dimers and/or their nuclear translocation.

Removal of copper by Pseudomonas putida strain S4 isolated from copper mines.

A bacterial strain, Pseudomonas putida S4, was isolated from smelter drainage of copper mines. The strain exhibited resistance to several heavy metals, like aluminium (Al), zinc (Zn), nickel (Ni), cobalt (Co) besides copper (Cu). Strain S4 could accumulate Cu from the Cu-supplemented growth medium. In the present study, we have demonstrated the Cu2+ removal capacity of this strain from various samples such as mine effluent, low-grade ore and ore-tailings, collected from the mining site. Moreover, approximately 80% of the accumulated Cu2+ could be recovered from the loaded biomass by a simple desorption procedure.

A rare prostaglandin from the soft coral Sarcophyton crassocaule of the Indian Ocean.

The rare prostaglandin methyl (5Z)-9,15-dioxoprosta-5, 8(12)-dien-1-oate (1), hitherto unreported as a natural product, has been isolated from the Indian Ocean soft coral Sarcophyton crassocaule. Its structure was elucidated using detailed spectral ((1)H and (13)C NMR, DEPT, H-H COSY, C-H COSY, HRMS, and HMBC) analysis.

Novel epoxy steroids from the indian ocean soft coral Sarcophyton crassocaule.

A detailed further examination of the Indian Ocean soft coral Sarcophyton crassocaule resulted in the isolation of altogether 17 compounds of which two (1 and 2) are novel 17beta,20beta-epoxy steroids and one is a new dihydroxygorgost-5-en (3). The other compounds include the four hippurin steroids (4-7) reported earlier, and some known derivatives such as methyl arachidonate, batyl alcohol, a mixture of monohydroxy sterols, 3beta-hydroxypregn-5-en-20-one, two prostaglandin derivatives (PGB(2) acid and its methyl ester), and 9-oxo-9, 11-secogorgost-5-ene-3beta,11-diol (8). The structure of new dihydroxygorgostene derivative was established as gorgost-5-ene-3beta,11alpha-diol (3), while the structures of the novel epoxy steroids were established as 17beta,20beta-epoxy-23, 24-dimethylcholest-5-ene-3beta,22-diol (2) and its 3beta, 22-diacetate (1), respectively.

Encapsulation as a response of Azospirillum brasilense sp7 to zinc stress.

Azospirillum brasilense sp7 was exposed to 2MM Zn(2+) in minimal medium upon which the cells turned black and non-motile within 24 h. A streptomycin-resistant variant did not exhibit this phenomenon and is sensitized to zinc. A prelude to encystation was the elution of a melanin-like pigment into the medium.