Colonic epithelium-enriched protein A4 is a proteolipid that exhibits ion channel characteristics

Expression of the human gene A4 is enriched in the colonic epithelium and is transcriptionally activated on differentiation of colonic epithelial cells in vitro (M. M. Oliva, T. C. Wu, and V. W. Yang. Arch. Biochem. Biophys. 302: 183-192, 1993). A4 cDNA contains an open reading frame that predicts a polypeptide of 17 kDa. To determine the function of the A4 protein, we characterized its biochemical and physiological properties. Hydropathy analysis of deduced A4 amino acid sequence revealed four putative membrane-spanning alpha-helices. The hydrophobic nature of A4 was confirmed by its being extractable with organic solvents. Immunocytochemical studies of cells expressing A4 localized it to the endoplasmic reticulum. Moreover, A4 multimerized in vivo as determined by coimmunoprecipitation experiments. The four-transmembrane topology and biophysical characteristics of A4 suggest that it belongs to a family of integral membrane proteins called proteolipids, some of which multimerize to form ion channels. Subsequent electrophysiological studies of nuclei isolated from microinjected Xenopus laevis oocytes transiently expressing A4 showed the appearance of a 28-pS channel. Thus our studies indicate that A4 is a colonic epithelium-enriched protein localized to the endoplasmic reticulum and that, similar to other proteolipids, A4 multimerizes and exhibits characteristics of an ion channel.

The class I alcohol dehydrogenase gene is glucocorticoid-responsive in the rat hepatoma microcell hybrid cell line, 11-3

Expression of the class I alcohol dehydrogenase (ADH) gene in the rat hepatoma microcell hybrid cell line, 11-3, was examined. The steady-state level of ADH mRNA in 11-3 was approximately 2-fold higher than that or rat liver and Fao, the parental cell line of 11-3. Removal of steroid hormones by activated charcoal from the serum in which 11-3 cells were maintained resulted in a significant decrease in the level of ADH transcript. Dexamethasone at a concentration of 1 muM increased the ADH mRNA content in 11-3 in a time-dependent fashion, up to 48 hr after its addition to cells that had first been deprived of steroid hormones. In addition, levels of ADH transcript in cells treated with dexamethasone increased in a dose-dependent manner, and the concentration of dexamethasone required to achieve half-maximal activation was 5 nM. By using the techniques of reverse transcription and polymerase chain reaction, and by taking advantage of a restriction polymorphism present between the rat and mouse ADH cDNA, we found that 11-3 contained both the rat and mouse class I ADH transcripts, although the rat sequence accounted for the great majority. Moreover, levels of both rat and mouse class I ADH transcripts increased in a similarly time-dependent manner in cells treated with dexamethasone. These results indicate that expression of class I ADH gene in 11-3 is high and is regulated by glucocorticoids, making the cell line an excellent model for the in vitro study of ADH expression.

Characterization of the 5'-flanking sequence of rat class I alcohol dehydrogenase gene

Expression of the rat class I alcohol dehydrogenase (ADH) gene is highest in the liver and regions of the intestine. We characterized over 3 kilobases of the gene's 5'-flanking region by sequencing and transient transfection. Alignment of the flanking sequence of the rat gene with those of the mouse and human class I genes revealed a cis-acting element, known to be a functional glucocorticoid response element in the human gene and conserved in the mouse, is interrupted in the rat promoter by a 490-base pair processed retropseudogene of the ribosomal protein S25. Southern analysis indicated that this inserted element is present in the class I ADH promoters of multiple strains of rat. Transfection analysis of the rat and mouse promoters showed that the mouse, but not the rat promoter, is inducible by dexamethasone. Electrophoretic mobility shift assays using nuclear extracts from dexamethasone-treated cells confirmed that the mouse's element interacts with the glucocorticoid receptor. Transient transfection of the 5'-flanking region of the rat gene linked to a human growth hormone reporter demonstrated the liver and intestinal specificity of the rat promoter. Two positive elements, one from nucleotides -1,327 to -977 and the other from -241 to -12, were shown to support high levels of reporter activity. In addition, a suppressive element was localized between nucleotides -403 and -241, a region of DNA situated within the domain of the S25 ribosomal protein pseudogene.

Conflicts, satisfactions, and attitudes during transition to the maternal role

A correlational descriptive study of 86 first-time mothers examined the relationships among employment status, role conflict, marital satisfaction, employment role attitude, and ease of transition to the maternal role. Interview and questionnaire data were collected 5 to 18 months after the birth of the first child. No significant differences were observed between employed and unemployed mothers in relation to role conflict. Mothers with careers tended to experience more role conflict between their worker, self, and spouse roles than mothers with jobs. Mothers who experienced more role conflict, regardless of their work status, had more difficulty in making the transition to the maternal role. Marital satisfaction was found to be positively correlated with ease of transition to the maternal role. No significant correlation was observed between employment role attitude and ease of transition to the maternal role. Mothers who reported a more positive attitude toward employment reported significantly less conflict between spouse and parent roles. Mothers who had attended a parent support group, regardless of their work status, experienced more conflict between the parent and self roles; these mothers also tended to have greater difficulty in making the transition to the maternal role.