LOCALIZATION OF THE RESPONSE ELEMENTS OF A GENE INDUCED BY INTERMITTENT GROWTH-HORMONE STIMULATION

Three regions required for the expression of a mouse major urinary pro tein (MUP) transgene were identified by a deletion analysis. One of th ese was located upstream of the cap site between -2139 and -1800, anot her was the proximal promoter region downstream of -324 and the third lay within the 338 nucleotide intron 1. Both the proximal promoter and intron 1 are involved in sexually dimorphic expression of the transge ne (male/female ratio 20), which is dictated by the different temporal profiles of circulating GH in the two sexes. The data also indicated that the region between exons 3 and 7 may contribute to full expressio n in males and that a region between -718 and -324 may contribute towa rds the low expression level that obtains in females, but compared wit h the three principal regions the effects of these regions are relativ ely minor. We propose (1) that full expression of the transgene requir es the co-operation of transcription factors binding to the three prin cipal regions and (2) that the difference in expression between the se xes relates to interactions between transcription factors bound to the proximal promoter and to sites in intron 1. Our results complement ea rlier in vitro footprinting and gel-retardation studies of the homolog ous rat alpha(2 alpha)-globulin genes. These identified a number of re sponse elements, including,putative C/EBP and AP1 sites in the proxima l promoter and intron 1 respectively and three putative psi NF-1 sites , two in the proximal promoter and one in intron 1, but proof of the f unctionality of these sites in regulating transcription was lacking. T he proximal promoter also contained a 34 nucleotide sequence that has 70% identity with the SPI GH response element.