Developmental and hormonal regulation of alpha 2u-globulin gene transcription

Molecular complexity of the major urinary protein system of the Norway rat, Rattus norvegicus

Major urinary proteins (MUP) are the major component of the urinary protein fraction in house mice (Mus spp.) and rats (Rattus spp.). The structure, polymorphism and functions of these lipocalins have been well described in the western European house mouse (Mus musculus domesticus), clarifying their role in semiochemical communication. The complexity of these roles in the mouse raises the question of similar functions in other rodents, including the Norway rat, Rattus norvegicus. Norway rats express MUPs in urine but information about specific MUP isoform sequences and functions is limited. In this study, we present a detailed molecular characterization of the MUP proteoforms expressed in the urine of two laboratory strains, Wistar Han and Brown Norway, and wild caught animals, using a combination of manual gene annotation, intact protein mass spectrometry and bottom-up mass spectrometry-based proteomic approaches. Cluster analysis shows the existence of only 10 predicted mup genes. Further, detailed sequencing of the urinary MUP isoforms reveals a less complex pattern of primary sequence polymorphism in the rat than the mouse. However, unlike the mouse, rat MUPs exhibit added complexity in the form of post-translational modifications, including the phosphorylation of Ser4 in some isoforms, and exoproteolytic trimming of specific isoforms. Our results raise the possibility that urinary MUPs may have different roles in rat chemical communication than those they play in the house mouse. Shotgun proteomics data are available via ProteomExchange with identifier PXD013986.

The neuroendocrinology of sexual attraction

Sexual attraction has two components: Emission of sexually attractive stimuli and responsiveness to these stimuli. In rodents, olfactory stimuli are necessary but not sufficient for attraction. We argue that body odors are far superior to odors from excreta (urine, feces) as sexual attractants. Body odors are produced by sebaceous glands all over the body surface and in specialized glands. In primates, visual stimuli, for example the sexual skin, are more important than olfactory. The role of gonadal hormones for the production of and responsiveness to odorants is well established. Both the androgen and the estrogen receptor α are important in male as well as in female rodents. Also in primates, gonadal hormones are necessary for the responsiveness to sexual attractants. In males, the androgen receptor is sufficient for sustaining responsiveness. In female non-human primates, estrogens are needed, whereas androgens seem to contribute to responsiveness in women.

α2u-globulins mediate manipulation of host attractiveness in Toxoplasma gondii-Rattus novergicus association

Uninfected female rats (Rattus novergicus) exhibit greater attraction to the males infected with protozoan parasite Toxoplasma gondii. This phenomenon is contrary to the aversion towards infected males observed in multitude of other host-parasite associations. In this report, we describe a proximate mechanism for this anomaly. We demonstrate that T. gondii infection enhances hepatic production and urinary excretion of α2u-globulins in rats. We further demonstrate that α2u-globulins are sufficient to recapitulate male sexual attractiveness akin to effects of the infection. This manipulation possibly results in greater horizontal transmission of this parasite between the infected male and the uninfected female. It supports the notion that in some evolutionary niches parasites can alter host sexual signaling, likely leading to an increased rate of sexual transmission.

The major urinary protein system in the rat

The genomes of rats and mice both contain a cluster of multiple genes that encode small (18–20 kDa) eight-stranded β-barrel lipocalins that are expressed in multiple secretory tissues, some of which enter urine via hepatic biosynthesis. These proteins have been given different names, but are mostly generically referred to as MUPs (major urinary proteins). The mouse MUP cluster is increasingly well understood, and, in particular, a number of roles for MUPs in chemical communication between conspecifics have been established. By contrast, the literature on the rat orthologues is much less well developed and is fragmented. In the present review, we summarize current knowledge on the MUPs from the Norway (or brown) rat, Rattus norvegicus.

Changes in male rat urinary protein profile during puberty: a pilot study

Background

Androgen-dependent proteins (lipocalins) circulate in blood of male rats and mice and, being small (~ 18 kDa), pass freely into glomerular filtrate. Some are salvaged in proximal nephrons but some escape in urine. Several organic molecules can bind to these proteins causing, where salvage occurs, nephropathy including malignancy in renal cortex. In urine, both free lipocalins and ligands contribute to an increasingly-recognised vital biological role in social communication between adults, especially in the dark where reliance is on smell and taste. Crystal structure of the first-characterised lipocalin of male rats, α2u-globulin, has been determined and peptide sequences for others are available, but no study of occurrence during early puberty has been made. We have followed temporal occurrence in urine of juveniles (n = 3) for non-invasive pilot study by high resolution gradient mini-gel electrophoresis, tryptic digest of excised protein bands, and LC-MS/MS of digest to identify peptide fragments and assign to specific lipocalins. Study objective refers directly to external availability for social communication but also indirectly to indicate kinetics of circulating lipocalins to which some xenobiotics may bind and constitute determinants of renal disease.

Results

Mini-gels revealed greater lipocalin complexity than hitherto recognised, possibly reflecting post-translational modifications. Earliest patterns comprised rat urinary protein 1, already evident in Sprague-Dawley and Wistar strains at 36 and 52 days, respectively. By 44 and 57 days major rat protein (α2u-globulin) occurred as the progressively more dominant protein, though as two forms with different electrophoretic mobility, characterised by seven peptide sequences. No significant change in urinary testosterone had occurred in Wistars when major rat protein became evident, but testosterone surged by 107 days concomitant with the marked abundance of excreted lipocalins.

Conclusions

Qualitative temporal changes in the composition of excreted lipocalins early in puberty, and apparent increase in major urinary protein as two resolvable forms, should catalyse systematic non-invasive study of urinary lipocalin and testosterone dynamics from early age, to illuminate this aspect of laboratory rodent social physiology. It could also define the potential temporal onset of nephrotoxic ligand risk, applicable to young animals used as toxicological models.

Dynamic in vivo binding of STAT5 to growth hormone-regulated genes in intact rat liver. Sex-specific binding at low- but not high-affinity STAT5 sites

Phylogenetic footprinting was used to predict functional transcription factor binding sites (TFBS) for signal transducer and activator of transcription (STAT) 5, a GH-activated transcription factor, in the GH-responsive genes IGF-I, SOCS2, and HNF6. Each gene, including upstream (100 kb) and downstream regions (25 kb), was aligned across four species and searched for conserved STAT5-binding sites using TFBS matrices. Predicted sites were classified as paired or single and whether or not they matched the STAT5 consensus sequence TTCN(3)GAA. Fifty-seven of the predicted genomic regions were assayed by chromatin immunoprecipitation from male rat liver with high STAT5 activity. STAT5 binding was enriched (up to 24-fold) at eight genomic regions of IGF-I, including three novel regions in the second intron, and at four regions of SOCS2, including three novel upstream sites. STAT5 binding to HNF6 was modestly enriched (up to 3-fold) at one consensus site and two novel, nonconsensus sites. Overall, 14 of 17 identified sites were paired STAT5 sites. STAT5 binding to these sites was dynamic in male rat liver, cycling on and off in response to each plasma GH pulse. Moreover, sex-specific STAT5 binding was apparent; in female rat liver, where nuclear STAT5 activity is generally low, STAT5 binding to IGF-I and SOCS2 was limited to high-affinity sites. Analysis of the verified STAT5 binding sites indicated that STAT5 TFBS matrix 459 in combination with a STAT5 consensus sequence was the best predictor of STAT5 binding to these three genes. Using these criteria, multiple novel STAT5 binding sites were identified and then verified in several other GH-inducible genes, including MUP genes, where male-specific gene expression was associated with male-specific STAT5 binding to multiple low-affinity STAT5 sites.

Chronic ethanol consumption upregulates the cytosolic and plasma membrane sialidase genes, but down regulates lysosomal membrane sialidase gene in rat liver

We have previously shown that chronic ethanol feeding stimulates liver cytosolic sialidase (CS) and plasma membrane sialidase (PMS), whereas it decreases lysosomal membrane sialidase (LMS) activities with concomitant alterations in their relative synthetic rate in rat. To understand the molecular mechanism(s) for these changes, we have evaluated the effect of ethanol administration in male Wistar rats as a function of increasing dietary ethanol concentration after 8 weeks of pair-feeding on (i) the expression of CS, PMS, and LMS genes by real-time quantitative polymerase chain reaction method; (ii) their relative transcription rates by nuclear run-on assay; and (iii) the actual amount of these sialidase proteins in the liver fractions of the respective groups by Western blot method. We have demonstrated that the animals fed with 10.6%, 20.8%, and 36% of total calories as ethanol showed a 20% (P<.05), 34% (P<.01), and 69% (P<.01) increase in CS mRNA level, and 22% (P<.05), 26% (P<.01), and 47% (P<.01) increase in PMS mRNA level, but a decrease in LMS mRNA level by 35% (P<.05), 50% (P<.01), and 80% (P<.01), respectively, as compared to controls. Western blot analyses of CS, PMS, and LMS in the liver subfractions showed that changes in protein levels of CS, LMS, and PMS were consistent with the corresponding changes in the respective mRNA levels. Thus, the upregulation of CS and PMS, but not LMS which is down regulated by chronic ethanol, may account for the appearance of asialoconjugates in alcoholics.

Changes in serum?2u-globulin levels in castrated male rats treated with testosterone propionate in a Hershberger assay

The Hershberger assay has been proposed as a candidate screening test method for the detection of androgenic and anti-androgenic chemicals and is being validated presently under the test guideline programme of the Organization for Economic Cooperation and Development (OECD). Rat alpha2u-globulin is male rat-specific protein appearing in their serum and urine, and the protein is known to be induced by androgens. We investigated the usefulness of measuring serum alpha2u-globulin levels as a parameter for the androgenic activity of chemicals tested in the Hershberger assay. The serum alpha2u-globulin level was measured after the administration of testosterone propionate at dosages of 0, 20, 100 or 500 microg kg(-1) day(-1) for ten consecutive days in the castrated male rats. The ventral prostate, balbocavernosus/levator ani muscles, glans penis and Cowper's gland were collected and weighed. Although all the androgen-responsive organ weights were increased significantly at dosages of 100 and 500 microg kg(-1) day(-1), the serum alpha2u-globulin level was increased significantly only at a dosage of 500 microg kg(-1) day(-1). These results show that the serum alpha2u-globulin level may be a useful biomarker for detecting androgenic activity caused by test chemicals, but it is less sensitive than the organ weights of androgen-responsive tissues in the Hershberger assay.

Development of a high-performance reporter plasmid for detection of chemicals with androgenic activity

A number of chemicals are present in the environment, and some synthetic chemicals may disrupt endocrine function of wild animals and humans. An effective procedure to screen chemicals for endocrine modulating activity has been needed to ensure the safety of chemicals, and the reporter gene assay technique may provide a powerful tool for screening endocrine-disrupting chemicals. We have developed a high-performance reporter plasmid that can trigger high androgen-dependent induction with high selectivity by using mouse mammary tumor virus (MMTV) androgen-responsive elements and a partial fragment of the rat alpha(2u)-globulin promoter region. This new type plasmid can induce higher transcriptional activation than a commercial PGV-P-based construct bearing the SV40 promoter fragment, and the basal induction level of this plasmid is much lower than that of the PGV-P-based construct. Moreover, only androgen derivatives could selectively induce a high response in the reporter gene assay with the new reporter plasmid. This new type of reporter plasmid, ARE-AUG- Luc+, should be of value in endocrine research and in screening to identify endocrine-modulating chemicals.

Differentially expressed transcripts in neoplastic hepatic nodules and neonatal rat liver studied by cDNA microarray analysis

The molecular mechanisms underlying hepatocarcinogenesis remain unclear. Wistar rats treated with 2-AAF develop hepatocarcinoma in histologically well-characterised stages. In our study, cDNA microarrays were used to measure the expression of 3,000 genes during the progression of liver carcinogenesis in persistent neoplastic nodules. Because tumours frequently revert into a more poorly differentiated phenotype, we also studied the expression of the same set of transcripts in neonatal rat liver. Approximately 2,000 transcripts gave a detectable signal in experiments comparing gene expression in nodules and control tissue. Approximately 8% of these were identified as differentially expressed in liver nodules. The differentially expressed genes fell into several categories with putative or demonstrated roles in signal transduction, metabolism, detoxification, cell-structure and transport. Many of the differentially expressed genes in nodules were not previously known to be regulated during liver carcinogenesis. A universal transcript profile for gene expression in hepatic liver nodules and neonatal liver has been created.

Hepatic alpha(2u)-globulin mRNA levels and diethylstilbestrol-associated testicular atrophy in rats

Biosynthesis of alpha(2u)-Globulin (alpha(2u)-g) is under multihormonal regulation. In this study, we investigated histopathologic changes in the testis and hepatic alpha(2u)-g messenger ribonucleic acid (mRNA) levels in male rats after administration of the potent estrogen diethylstilbestrol (DES) at 0. 01, 0.1, or 1 mg/kg/day by gavage for 14 days. DES treatment decreased hepatic alpha(2u)-g mRNA levels in a dose-dependent manner accompanied by atrophic histopathologic changes in the testis. In addition, alpha(2u)-g mRNA levels were lowest in animals with the most marked testicular changes. Hepatic alpha(2u)-g mRNA may be a useful biomarker for the evaluation of endocrine disruption in male rats.

Molecular evidence of complex tissue- and sex-specific mRNA expression of the rat alpha(2u)-globulin multigene family

alpha(2u)-Globulin is well known to be a rat protein encoded by a highly homologous multigene family with more than twenty members. We report here the cloning and identification of major alpha(2u)-globulin mRNA species expressed in various tissues. Initially, eight individual clones (PGCL1-8) were obtained from a male preputial gland cDNA library. Data base analysis with BLAST demonstrated six mRNAs to be novel, all clones being characterized by highly conserved sequence motifs as lipocalins. All cDNAs contained an open reading frame of 543 nucleotides and encode 181 amino acid proteins showing 92.5-98.7% and 87.3-98.3% nucleic and amino acid identity, respectively. Denaturing gradient gel electrophoresis (DGGE) with sequence analysis showed that PGCL4 is a major member in the female mammary gland, and in the submaxillary and lachrymal glands of both sexes, while the counterpart in male liver and the coagulate glands was found to be PGCL1. Numbers of cDNA species including PGCL1 and PGCL4 were found in preputial glands, no sex-related difference being observed. These results directly demonstrate complex tissue- and sex-specific expression of alpha(2u)-globulins in terms of mRNA species, providing useful information for understanding regulation of the alpha(2u)-globulin multigene family.

Requirement of STAT5b for sexual dimorphism of body growth rates and liver gene expression

The signal transducer and activator of transcription, STAT5b, has been implicated in signal transduction pathways for a number of cytokines and growth factors, including growth hormone (GH). Pulsatile but not continuous GH exposure activates liver STAT5b by tyrosine phosphorylation, leading to dimerization, nuclear translocation, and transcriptional activation of the STAT, which is proposed to play a key role in regulating the sexual dimorphism of liver gene expression induced by pulsatile plasma GH. We have evaluated the importance of STAT5b for the physiological effects of GH pulses using a mouse gene knockout model. STAT5b gene disruption led to a major loss of multiple, sexually differentiated responses associated with the sexually dimorphic pattern of pituitary GH secretion. Male-characteristic body growth rates and male-specific liver gene expression were decreased to wild-type female levels in STAT5b-/- males, while female-predominant liver gene products were increased to a level intermediate between wild-type male and female levels. Although these responses are similar to those observed in GH-deficient Little mice, STAT5b-/- mice are not GH-deficient, suggesting that they may be GH pulse-resistant. Indeed, the dwarfism, elevated plasma GH, low plasma insulin-like growth factor I, and development of obesity seen in STAT5b-/- mice are all characteristics of Laron-type dwarfism, a human GH-resistance disease generally associated with a defective GH receptor. The requirement of STAT5b to maintain sexual dimorphism of body growth rates and liver gene expression suggests that STAT5b may be the major, if not the sole, STAT protein that mediates the sexually dimorphic effects of GH pulses in liver and perhaps other target tissues. STAT5b thus has unique physiological functions for which, surprisingly, the highly homologous STAT5a is unable to substitute.

Differential regulation of the cytochrome P450 3A1 gene transcription by dexamethasone in immature and adult rat liver

We have previously shown that the in vivo induction of cytochrome P450 3A1 by dexamethasone occurs through a sharp and early transcriptional activation in the immature rat liver that is drastically impaired in adults [Telhada, M. B., Pereira, T. M. & Lechner, M. C. (1992) Arch. Biochem. Biophys. 298, 714-725]. In the present study we investigate the relative importance of cytochrome P450 3A1 gene transcription on the adaptive response to the synthetic glucocorticoid dexamethasone, by measuring the time-course run-on transcription rate and concomitant mRNA accumulation in the male rat liver at two different ontological developmental stages. The primary (direct) or secondary (dependent on protein neo-synthesis) nature of the in vivo inductive response to dexamethasone and to pregnenolone 16 alpha-carbonitrile, is further investigated by inhibiting translation by cycloheximide pretreatment. The induction of cytochrome P450 3A1 gene transcription by the anti-glucocorticoid pregnenolone 16 alpha-carbonitrile is demonstrated to occur through a secondary mechanism, requiring ongoing protein biosynthesis, regardless of the developmental stage of the animals. Conversely, a significant developmentally controlled change is observed in the inductive response of the cytochrome P450 3A1 gene to dexamethasone, characterized by a markedly delayed transcriptional activation in the adult rat liver (90 day old) as compared to the immature rat liver (21 day old). This is consistent with the net primary response of the cytochrome P450 3A1 gene to dexamethasone demonstrated in this study to occur in the immature rat liver and almost lost at the adult stage, when protein neo-synthesis becomes essential for the inductive response. Our results demonstrate (a) a difference in the mechanisms underlying induction of the cytochrome P450 3A1 gene by the glucocorticoid agonist dexamethasone and by the antagonist pregnenolone 16 alpha-carbonitrile, and (b) an important change in the mechanisms of the inductive response to dexamethasone, associated with the immature/adult liver phenotype transition. This indicates the participation of specific labile transcription factors in the induction of cytochrome P450 3A1 gene by the synthetic glucocorticoids.

Purified glucocorticoid receptors bind selectively in vitro to a cloned DNA fragment that mediates a delayed secondary response to glucocorticoids in vivo

We have identified and characterized a 206-base-pair region downstream from rat alpha 2u-globulin promoter that specifically mediates a delayed secondary response to glucocorticoids. Unlike positive primary glucocorticoid response elements (GREs), this regulatory element, termed delayed sGRE, dictates an inductive process preceded by a time lag of several hours and blocked by the protein synthesis inhibitor cycloheximide. Reminiscent of GREs and negative GREs (nGREs), a delayed sGRE confers hormonal regulation upon a linked heterologous promoter from a downstream position with respect to transcription start site and, remarkably, also interacts selectively with purified glucocorticoid receptor. These results imply that receptor binding to a delayed sGRE in vivo may mediate certain secondary responses to glucocorticoid hormones.

T-kininogen gene expression is induced during aging

We have constructed a cDNA library from senescent (24-month-old) rat liver mRNA and, by differential screening, have selected clones corresponding to mRNA species with increased abundance in aging rats. Direct sequencing of the inserts indicated that most of the clones (9 of 10) contained sequences coding for T-kininogen, also called major acute-phase protein, cysteine protease inhibitor, or thiostatin. Nuclear elongation experiments showed that the increase in mRNA concentration was controlled at the transcriptional level. RNase mapping and S1 analysis indicated that the age-dependent induction operated preferentially at one of the three transcriptional start sites of the gene(s). The acute-phase reaction (inflammation) is known to also induce these genes at the level of transcription; however, two of the three start sites are induced by inflammation. Transcription from one of these sites was induced by both phenomena, aging and inflammation.

T-kininogen gene expression is induced during aging

We have constructed a cDNA library from senescent (24-month-old) rat liver mRNA and, by differential screening, have selected clones corresponding to mRNA species with increased abundance in aging rats. Direct sequencing of the inserts indicated that most of the clones (9 of 10) contained sequences coding for T-kininogen, also called major acute-phase protein, cysteine protease inhibitor, or thiostatin. Nuclear elongation experiments showed that the increase in mRNA concentration was controlled at the transcriptional level. RNase mapping and S1 analysis indicated that the age-dependent induction operated preferentially at one of the three transcriptional start sites of the gene(s). The acute-phase reaction (inflammation) is known to also induce these genes at the level of transcription; however, two of the three start sites are induced by inflammation. Transcription from one of these sites was induced by both phenomena, aging and inflammation.

Expression of a constitutive form of cytochrome P450 during rat-liver development and sexual maturation

Cytochrome P450 cDNA clone designated pP450 IGC 1 has been previously isolated from a phenobarbital-induced rat liver cDNA library, characterized and proven to correspond to a constitutive cytochrome P450 sensitive to phenobarbital stimulation. IGC 1 pDNA, as well as a unique synthetic oligonucleotide probe, were used to investigate the mRNA levels at different developmental stages (fetal, male and female rats of various ages) in parallel with the study of the expression of the liver development and male phenotype markers: albumin, alpha-fetoprotein and alpha 2u globulin mRNAs. Cytochrome P450 IGC 1 mRNA responsiveness to phenobarbital administration was studied in animals of both sexes at different developmental stages. P450 IGC 1 mRNA was not detectable in fetuses nor in male or female rat liver before sexual maturation, becoming elevated at 45 days age, increasing up to 3 months and reaching relatively higher levels in the female liver than in the male. The concentrations of P450 IGC 1 mRNA closely paralleled the increases in alpha 2u globulin mRNA in male liver, as analyzed by dot and Northern blot hybridization. However, P450 IGC 1 was markedly induced by phenobarbital already at 20 days age both in males and females while alpha 2u globulin mRNA was not inducible before sexual maturation. It is concluded that the expression of cytochrome P450 IGC 1 mRNA is associated with the sexual maturation being differently modulated in the male and in the female rat liver. This cytochrome P450 isoenzyme may play an important physiological role in sex differential steroid metabolism and susceptibility to cytotoxic and genotoxic agents.

Tissue-specific and hormonally regulated expression of a rat alpha 2u globulin gene in transgenic mice

To investigate the tissue-specific and hormonal regulation of the rat alpha 2u globulin gene family, we introduced one cloned member of the gene family into the mouse germ line and studied its expression in the resulting transgenic mice. Alpha 2u globulingene 207 was microinjected on a 7-kilobase DNA fragment, and four transgenic lines were analyzed. The transgene was expressed at very high levels, specifically in the liver and the preputial gland of adult male mice. The expression in male liver was first detected at puberty, and no expression was detected in female transgenic mice. This pattern of expression is similar to the expression of endogenous alpha 2u globulin genes in the rat but differs from the expression of the homologous mouse major urinary protein (MUP) gene family in that MUPs are synthesized in female liver and not in the male preputial gland. We conclude that these differences between rat alpha 2u globulin and mouse MUP gene expression are due to evolutionary differences in cis-acting regulatory elements. The expression of the alpha 2u globulin transgene in the liver was abolished by castration and fully restored after testosterone replacement. The expression could also be induced in the livers of female mice by treatment with either testosterone or dexamethasone, following ovariectomy and adrenalectomy. Therefore, the cis-acting elements responsible for regulation by these two hormones, as well as those responsible for tissue-specific expression, are closely linked to the alpha 2u globulin gene.

Cellular mechanism of action of thyroid hormones

It has emerged in the last decade that the molecular mechanism of action of thyroid hormones resembles that of steroids; thyroid hormones indeed exert their effects mainly by directly regulating gene expression, on association with specific chromatin-bound receptors. Of the two thyroid hormones, thyroxine (T4) appears to be a sort of prohormone, whereas triiodothyronine (T3) seems to be the active form; in this respect, T4-deiodination, which occurs at the level of the target tissues, may be crucial in the local homeostasis of T3. Moreover, many cellular compartments, other than the nucleus, can bind thyroid hormone, and at least some of these further sites might play some role in modulating T3 supply to the nucleus. The binding of the T3-receptor complex to chromatin is likely to regulate the structural organization of specific genes and, in some instances, of the chromatin as a whole.

Tissue-specific and hormonally regulated expression of a rat alpha 2u globulin gene in transgenic mice

To investigate the tissue-specific and hormonal regulation of the rat alpha 2u globulin gene family, we introduced one cloned member of the gene family into the mouse germ line and studied its expression in the resulting transgenic mice. Alpha 2u globulingene 207 was microinjected on a 7-kilobase DNA fragment, and four transgenic lines were analyzed. The transgene was expressed at very high levels, specifically in the liver and the preputial gland of adult male mice. The expression in male liver was first detected at puberty, and no expression was detected in female transgenic mice. This pattern of expression is similar to the expression of endogenous alpha 2u globulin genes in the rat but differs from the expression of the homologous mouse major urinary protein (MUP) gene family in that MUPs are synthesized in female liver and not in the male preputial gland. We conclude that these differences between rat alpha 2u globulin and mouse MUP gene expression are due to evolutionary differences in cis-acting regulatory elements. The expression of the alpha 2u globulin transgene in the liver was abolished by castration and fully restored after testosterone replacement. The expression could also be induced in the livers of female mice by treatment with either testosterone or dexamethasone, following ovariectomy and adrenalectomy. Therefore, the cis-acting elements responsible for regulation by these two hormones, as well as those responsible for tissue-specific expression, are closely linked to the alpha 2u globulin gene.

Nucleotide sequences required for the regulation of a rat alpha 2u-globulin gene by glucocorticoids

alpha 2u-Globulin is a rat protein of as yet unknown function whose synthesis can be induced by glucocorticoids and several other hormones. Induction by glucocorticoids is a secondary response to the hormone: protein synthesis is required before the hormone can exert its stimulatory effect on alpha 2u-globulin transcription. We have used the linker-scanning mutagenesis procedure, followed by transfer of the mutant genes into mouse L-cells for analysis of their phenotype, to determine sequences within a cloned alpha 2u-globulin promoter that are required for its regulation by glucocorticoids. Mutations between positions -115 and -160 abolish or greatly reduce the inducibility of alpha 2u-globulin by the hormone. Mutations just upstream from this region, between positions -177 and -220, have an opposite effect; they increase induction two- to fourfold.

Nucleotide sequences required for the regulation of a rat alpha 2u-globulin gene by glucocorticoids

alpha 2u-Globulin is a rat protein of as yet unknown function whose synthesis can be induced by glucocorticoids and several other hormones. Induction by glucocorticoids is a secondary response to the hormone: protein synthesis is required before the hormone can exert its stimulatory effect on alpha 2u-globulin transcription. We have used the linker-scanning mutagenesis procedure, followed by transfer of the mutant genes into mouse L-cells for analysis of their phenotype, to determine sequences within a cloned alpha 2u-globulin promoter that are required for its regulation by glucocorticoids. Mutations between positions -115 and -160 abolish or greatly reduce the inducibility of alpha 2u-globulin by the hormone. Mutations just upstream from this region, between positions -177 and -220, have an opposite effect; they increase induction two- to fourfold.