Role of prolactin in the transcription of beta-casein and 28-S ribosomal genes in the rabbit mammary gland.
Isolated mammary nuclei were incubated in the presence of HgCTP and the neosynthesized RNA was isolated with a SH-Sepharose column. The concentration of beta-casein mRNA and 28-S ribosomal RNA in the neosynthesized RNA fractions was evaluated using [3H]DNA probes complementary to beta-casein mRNA and 28-S rRNA respectively. In the unstimulated pseudopregnant rabbit, the transcription of both genes was easily detectable. Injections of prolactin progressively enhanced the transcription rate of both genes and preferentially the beta-casein gene. A comparison between the transcription rates and the accumulation of the corresponding gene products in the cell revealed that there is a good correlation between these two parameters for the 28-S rRNA gene. By contrast, the acceleration of beta-casein gene transcription by prolactin is unable to account for the simultaneous accumulation of beta-casein mRNA, indicating that prolactin is a potent stabilizer of casein mRNA. Injections of CB154 into lactating rabbits (a drug which suppresses the secretion of prolactin by hypophysis), induced a rapid drop of beta-casein mRNA concentration and a slow decline of beta-casein gene transcription. Simultaneously the drug was responsible for a marked and rapid decrease of 28-S rRNA gene transcription, while the concentration of the rRNA remained elevated. During weaning the transcription of the beta-casein gene and, to a lower degree, the transcripton of the 28-S rRNA gene proceeded more slowly and this phenomenon was accompanied by a progressive decline of the RNA concentrations.
D000818:Animals; D001971:Bromocriptine / Q000494:pharmacology; D002364:Caseins / Q000096:biosynthesis*; D005260:Female; D007774:Lactation; D008321:Mammary Glands, Animal / Q000378:metabolism*; D011247:Pregnancy; D011388:Prolactin / Q000494:pharmacology*; D011555:Pseudopregnancy / Q000378:metabolism; D012333:RNA, Messenger / Q000096:biosynthesis; D012335:RNA, Ribosomal / Q000096:biosynthesis*; D011817:Rabbits; D014158:Transcription, Genetic / Q000187:drug effects*; D014886:Weaning
D002364:Caseins; D012333:RNA, Messenger; D012335:RNA, Ribosomal; D001971:Bromocriptine; D011388:Prolactin