Although steroid hormone receptors are known to activate gene expression by binding to specific hormone-dependent enhancers, the mechanisms by which steroids inhibit the transcription of specific genes are unknown. It is shown here by gene transfer studies that the same glucocorticoid receptor that activates gene expression can negatively regulate expression of the human glycoprotein hormone alpha-subunit gene. Glucocorticoid inhibition was conferred by a 52-nucleotide region that also contains elements crucial both for adenosine 3',5'-monophosphate (cAMP) responsiveness and for placental-specific expression of this gene and was observed only under conditions in which these elements were functioning as enhancers. Purified glucocorticoid receptor was found to bind to DNA that overlap the cAMP responsive elements sites in this region. It is hypothesized that steroid receptors negatively regulate gene expression by interfering with the activity or binding of other important transcription factors.

Eosinophils are important effector cells in defense against helminth infection and in allergic diseases. To identify novel eosinophil proteins, large scale sequencing of a cDNA library prepared from interleukin-5-stimulated umbilical cord precursor cells was performed, and the major genes expressed by maturing eosinophils were determined. This resulted in the identification of a cDNA with 64% identity to human prepro-major basic protein (hprepro-MBP). This cDNA was designated hprepro-MBP homolog (hprepro-MBPH). Interestingly, the calculated pI values for hMBPH and hMBP differed by >100-fold, with pI values of 8.7 and 11.4, respectively. Given this pronounced basicity difference, the homolog transcript's abundance (1.1%), and MBP's critical role in eosinophil biological activity, we further characterized the homolog. Reverse transcription-polymerase chain reaction detected transcription of hprepro-MBPH in bone marrow only, and this result was confirmed by analysis of a large cDNA data base (electronic Northern). hMBPH was isolated from human eosinophil granule lysates, and its identity was verified by amino acid sequencing and by mass spectrometry. Analyses of the biological activities showed that hMBPH had effects similar to hMBP in cell killing and neutrophil (superoxide anion production and interleukin-8 release) and basophil (histamine and leukotriene C 4 release) stimulation assays, but usually with reduced potency. Overall, this novel homolog's unique physical properties indicated that the high net positive charge of hMBP is important but not essential for biological activity.

The leptin receptor (OB-R) is a single membrane- spanning protein that mediates the weight-regulatory effects of leptin (OB protein). Several mRNA splice variants have been described which either encode OB-R proteins with cytoplasmic domains of different length or the OB-R and B219/OBR variants, which have different 5'-untranslated regions. Here we report evidence for the synthesis of a human mRNA splice variant of the OB-R gene that potentially encodes a novel protein, leptin receptor gene-related protein (OB-RGRP), which displays no sequence similarity to the leptin receptor itself. This OB-RGRP transcript contains the first two OB-R gene 5'-untranslated exons, but then is alternatively spliced to two novel exons which were mapped to a yeast artificial chromosome containing the leptin receptor gene. First identified by analysis of a large human expressed sequence tag database, the OB-RGRP transcript has now also been found in human and mouse tissues by the use of PCR. Preliminary experiments suggest that OB-RGRP and the OB-R variants share similar patterns of expression that are distinct from that of the B219/OBR variant. OB-RGRP is highly homologous to putative open reading frames in both yeast and Caenorhabditis elegans , suggesting a phylogenetically conserved role for this novel protein.

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