• The Korean Journal of Zoology
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• v.38 no.3
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• pp.426-432
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• 1995

Expression of $\beta$-lactoglobulin gene in mammary tissue is strongly induced by lactogenic hormones such as prolactin, glucocorticoid, and insulin. In order to elucidate the regulatory mechanism underlying such hormonal induction, the response of the caprine $\beta$-lactoglobulin gene promoter to lactogenic hormones was analyzed in cultured HC11 mammary cells. Expression with serial deletions of the 5' -regulatory sequence of the $\beta$-lactoglobulin promoter revealed that two regions are responsible for a substantial change in hormonal indudbility. The region upstream of-1692, which exhibited strong repression of the downstream promoter, mediated the induction by insulin. This insulin-response was independent of the other two lactogenic hormones, prolactin and glucocorticoid. The other region from -740 to -470, which showed strong activation of the $\beta$-lactoglobulin promoter in confluent HC11 mammary cells, mediated mainly the response to a glucocorticoid analogue, dexametasone. The induction by the latter region, however, was suppressed by the usptream repression without insulin treatment. These results suggest that the induction of $\beta$-lactoglobulin promoter activity by lactogenic hormones in mammary cells may be achieved by the combined action of derepression by in sulin and activation by glucocorticoid and prolactin. Dexametasone response by the latter region seems to be mediated by the glucocorticoid receptor site around -7OObp.