MicroRNAs are a recently discovered class of posttranscriptional regulators of gene expression with critical functions in health and disease. Psoriasis is the most prevalent chronic inflammatory skin disease in adults, with a substantial negative impact on the patients' quality of life. Here we show for the first time that psoriasis-affected skin has a specific microRNA expression profile when compared with healthy human skin or with another chronic inflammatory skin disease, atopic eczema. Among the psoriasis-specific microRNAs, we identified leukocyte-derived microRNAs and one keratinocyte-derived microRNA, miR-203. In a panel of 21 different human organs and tissues, miR-203 showed a highly skin-specific expression profile. Among the cellular constituents of the skin, it was exclusively expressed by keratinocytes. The up-regulation of miR-203 in psoriatic plaques was concurrent with the down-regulation of an evolutionary conserved target of miR-203, suppressor of cytokine signaling 3 (SOCS-3), which is involved in inflammatory responses and keratinocyte functions. Our results suggest that microRNA deregulation is involved in the pathogenesis of psoriasis and contributes to the dysfunction of the cross talk between resident and infiltrating cells. Taken together, a new layer of regulatory mechanisms is involved in the pathogenesis of chronic inflammatory skin diseases.

Recombinant clones containing exon 3 of the insulin-like growth factor I (IGF-I) gene were isolated from a mouse genomic library. These sequences were used to generate an RNA probe, which was used in a solution hybridization assay to quantitate IGF-I mRNA in various murine tissues as a function of growth hormone status. The liver is the major site of IGF-I synthesis and the level of IGF-I mRNA is regulated about 10-fold by growth hormone in the growth hormonedeficient lit/lit mouse. Nuclear run-on assays were used to show that growth hormone regulation is manifested in part at the transcriptional level. Growth hormone also affects the size distribution of hepatic IGF-I mRNAs. Pancreas showed the highest non-hepatic expression, but every tissue analyzed contained some IGF-I mRNA. Expression was not growth hormone-dependent in most non-hepatic tissues.

The molecular components which mediate cytokine signaling from the cell membrane to the nucleus were studied. Upon the interaction of cytokines with their receptors, members of the janus kinase (Jak) family of cytoplasmic protein tyrosine kinases and of the signal transducers and activators of transcription (Stat) family of transcription factors are activated through tyrosine phosphorylation. It has been suggested that the Stat proteins are substrates of the Jak protein tyrosine kinases. MGF‐Stat5 is a member of the Stat family which has been found to confer the prolactin response. MGF‐Stat5 can be phosphorylated and activated in its DNA binding activity by Jak2. The activation of MGF‐Stat5 is not restricted to prolactin. Erythropoietin (EPO) and growth hormone (GH) stimulate the DNA binding activity of MGF‐Stat5 in COS cells transfected with vectors encoding EPO receptor and MGF‐Stat5 or vectors encoding GH receptor and MGF‐Stat5. The activation of DNA binding by prolactin, EPO and GH requires the phosphorylation of tyrosine residue 694 of MGF‐Stat5. The transcriptional induction of a beta‐casein promoter luciferase construct in transiently transfected COS cells is specific for the prolactin activation of MGF‐Stat5; it is not observed in EPO‐ and GH‐treated cells. In the UT7 human hematopoietic cell line, EPO and granulocyte‐macrophage colony stimulating factor activate the DNA binding activity of a factor closely related to MGF‐Stat5 with respect to its immunological reactivity, DNA binding specificity and molecular weight. These results suggest that MGF‐Stat5 regulates physiological processes in mammary epithelial cells, as well as in hematopoietic cells.(ABSTRACT TRUNCATED AT 250 WORDS)

The mouse metallothionein II (MT-H) gene is located -6 kilobases upstream of the MT-I gene. A comparison of the sequences of mouse MT-I and MT-II genes (as well as those of other mammals) reveals that the coding regions are highly conserved even at "silent" positions but that the noncoding regions and introns are extremely divergent between primates and rodents. There are four blocks of conserved sequences in the promoters of mouse MT-I, mouse MT-II, and human MT-IIA genes; one includes the TATAAA sequence, and another has been implicated in regulation by heavy metals. Mouse MT-I and MT-II mRNAs are induced to approximately the same extent in vivo in response to cadmium, dexamethasone, or lipopolysaccharide. Mouse MT-I and MT-II genes are regulated by metals but not by glucocorticoids after transfection into HeLa cells.

The promoter or regulatory region of the mouse gene for metallothionein-I was fused to the structural gene coding for human growth hormone. These fusion genes were introduced into mice by microinjection of fertilized eggs. Twenty-three (70 percent) of the mice that stably incorporated the fusion genes showed high concentrations of human growth hormone in their serum and grew significantly larger than control mice. Synthesis of human growth hormone was induced further by cadmium or zinc, which normally induce metallothionein gene expression. Transgenic mice that expressed human growth hormone also showed increased concentrations of insulin-like growth factor I in their serum. Histology of their pituitaries suggests dysfunction of the cells that normally synthesize growth hormone. The fusion genes were expressed in all tissues examined, but the ratio of human growth hormone messenger RNA to endogenous metallothionein-I messenger RNA varied among different tissues and different animals, suggesting that expression of the foreign genes is influenced by site of integration and tissue environment.