Oct-1 functions as a transactivator in the hormonal induction of beta-casein gene expression.
The ubiquitous transcription factor Oct-1 is involved in the hormonal regulation of the transcription of the major milk protein beta-casein through an interaction with the prolactin receptor, the STAT-5, and the glucocorticoid receptor (GR). In this study, this interaction was further demonstrated using Oct-1-deficient cells. In addition, Oct-1 mRNA expression is shown to increase during pregnancy and reach the highest levels during early lactation in mouse mammary gland. In reconstituted COS-7 cells, the endogenous Oct-1 binding activity rapidly increased within 5 min upon the lactogenic hormone treatment, indicating potential post-transcriptional/translational modification of Oct-1 by prolactin and glucocorticoids. Furthermore, STAT-5B was as effective as STAT-5A in the interaction with Oct-1 during hormonal induction, and a GR mutant, which carries mutations at multiple potential phosphorylation sites, functioned similarly to the wild-type GR, indicating that these phosphorylation sites may not be involved in the interaction of GR with Oct-1 on the beta-casein gene promoter.
Dong
Bing
B
Department of Animal Science, University of Vermont, Burlington, 05405, USA.
Huang
Chengfei
C
Li
Defa
D
Zhao
Feng-Qi
FQ
D000818:Animals; D019556:COS Cells; D002364:Caseins / Q000096:biosynthesis*; D002522:Chlorocebus aethiops; D005260:Female; D005938:Glucocorticoids / Q000494:pharmacology; D006728:Hormones / Q000494:pharmacology*; D008321:Mammary Glands, Animal / Q000378:metabolism / Q000502:physiology; D051379:Mice; D008810:Mice, Inbred C57BL; D050811:Octamer Transcription Factor-1 / Q000502:physiology*; D011247:Pregnancy; D011388:Prolactin / Q000494:pharmacology; D011401:Promoter Regions, Genetic; D012333:RNA, Messenger / Q000032:analysis; D011965:Receptors, Glucocorticoid / Q000378:metabolism; D011981:Receptors, Prolactin / Q000378:metabolism; D050799:STAT5 Transcription Factor / Q000378:metabolism; D015534:Trans-Activators / Q000502:physiology*; D015533:Transcriptional Activation / Q000187:drug effects*
D002364:Caseins; D005938:Glucocorticoids; D006728:Hormones; D050811:Octamer Transcription Factor-1; D012333:RNA, Messenger; D011965:Receptors, Glucocorticoid; D011981:Receptors, Prolactin; D050799:STAT5 Transcription Factor; D015534:Trans-Activators; D011388:Prolactin