Prostatic binding protein (PBP), a hormonally controlled oligomeric glycoprotein secreted by the rat ventral prostate, is composed of three different polypeptide chains, C1, C2, and C3. Microinjection of prostate mRNA into Xenopus laevis oocytes results in the synthesis, processing, and correct assembly of these three components, and also in the export of PBP into the medium. The glycosylation of component C3--the only glycopeptide of PBP--by the oocyte enzymes does not lead to the same result as in the native prostate tissue. The intracellular oocyte component contains an incompletely processed oligomannosyl core unit. Upon secretion this sugar core is further processed, probably at random because the carbohydrate chains attached to the exported C3 molecules are heterogeneous; they are also different from the oligosaccharide unit of authentic C3. However, tunicamycin experiments show that glycosylation is neither a prerequisite for secretion nor for the assembly of PBP, at least in oocytes.
Rat prostatic binding protein genes C1, C2, and C3 were mapped on rat chromosome 5 by in situ hybridization on rat peripheral blood chromosome preparations using three different cDNA probes. Of the grains detected, 15.9%, 25.2%, and 19.6%, respectively, mapped to chromosome 5. For each probe, the label was predominantly located on 5q31, but for C2 and C3 an additional site on 5q21 was found. The results suggest that three genes coding for the different polypeptide chains of rat prostatic binding protein map to the same chromosome and presumably to the same chromosome band.
Two genes encoding rat cystatin-related prostate protein (Cstrp), previously called CRP (Devos et al., 1993), were mapped to chromosome 3q41 by fluorescent in situ hybridization. The results were confirmed using a panel of mouse-rat hybrids that segregate rat chromosomes. Analysis of genomic DNA indicates that the Cstrp locus comprises probably more than three very similar genes.
The androgen and glucocorticoid receptors recognize identical DNA motifs, leaving unanswered the question of how steroid specificity of transcriptional regulation is established in cells containing both receptors. Here, we provide evidence that subtle differences in low affinity DNA recognition might be a crucial element in the generation of steroid-specific responses. Here we identify simple hormone response elements in the mouse sex-limited protein enhancer and the human secretory component androgen response unit to be essential for the androgen specificity of both enhancers. We describe specific in vitro binding to these motifs by the DNA-binding domain of the androgen but not the glucocorticoid receptor. Both elements can be considered partial direct repeats of the 5′-TGTTCT-3′ core binding motif. In addition, we show that specific point mutations in their left half-sites, essentially changing the nature of the repeats, strongly enhance the glucocorticoid sensitivity of the respective enhancers, whereas they have no effect on their androgen responsiveness. Accordingly, these mutations allow specific binding of the glucocorticoid receptor DNA-binding domain to both elements in vitro. With these experiments, we demonstrate that differential recognition by the androgen receptor of nonconventional steroid response elements is, at least in some cases, an important mechanism in androgen-specific transcriptional regulation.
The maternal and fetal endocrine pancreas were investigated in the diabetic BB rat on day 21 of pregnancy. The maternal pancreas of the diabetic rat contained practically no insulin-positive B cells. The A and D cell mass were also decreased, while plasma glucagon and somatostatin levels were normal or increased, confirming previous data. Six of 11 diabetic rats had B-cell-specific surface antibodies (ICSA), whereas only 1 of 10 nondiabetic rats was ICSA-positive. The volume density of insulin-positive cells was decreased in the fetal pancreas of diabetic BB rats compared to fetuses of nondiabetic rats, but the volume density of glucagon- and somatostatin-positive cells remained normal. The B cells of these fetuses were ultrastructurally less granulated and showed signs of increased cellular activity. Plasma insulin levels were decreased while plasma glucagon and somatostatin concentrations were normal. ICSA were not detected in fetuses of nondiabetic and diabetic rats. There were no differences in the histology of the spleen and thymus between both groups of fetuses. Metabolic characterization of the growth-retarded fetuses of diabetic rats revealed, besides lower plasma insulin concentrations, increased branched chain amino acid levels, and normal plasma Sm/IGF-I levels. The main conclusions from this study are: (1) Severe maternal diabetes decreases the pancreatic insulin-positive cell mass and plasma insulin levels in the fetus, but not the A and D cell mass and function; (2) ICSA are not detectable in fetal plasma; (3) the influence of maternal BB rat diabetes on fetal endocrine pancreas and metabolic environment resembles that of severe streptozotocin-induced diabetes.
