Prolactin, epidermal growth factor or transforming growth factor-alpha activate a mammary cell-specific enhancer in mouse mammary tumor virus-long terminal repeat.
Mammary specific expression of elevated levels of mouse mammary tumor virus (MMTV) contributes to mammary carcinogenesis. Mechanisms which regulate provirus expression have not been completely defined. Using a MMTV-long repeat terminal (MMTV-LRT) directed chloramphenicol-acetyltransferase (CAT) reporter gene system and a human breast cancer cell line T47D, we demonstrate that prolactin (PRL), epidermal growth factor (EGF), or transforming growth factor-alpha (TGF-alpha) act on a mammary cell-specific enhancer at the extreme 5' end of the MMTV-LTR involving sequences -1094 through -858. PRL and either EGF or TGF-alpha exert concerted roles in this activation of these sequences. In contrast, using a plasmid construct lacking this mammary cell-specific enhancer, EGF or TGF-alpha, but not PRL, act synergistically with progesterone to induce CAT activity, indicating that the action of PRL on regulatory elements of the MMTV-LTR is restricted to this mammary cell-specific enhancer involving sequences -1094 through -858. A mobility shift assay was used to demonstrate that PRL, EGF or TGF-alpha induce nuclear factors (MP4, MAF, and MGF) which bind directly to this mammary cell-specific enhancer element.
Haraguchi
S
S
Department of Pediatrics, All Children's Hospital, University of South Florida College of Medicine, St. Petersburg 33701, USA.
Good
R A
RA
Engelman
R W
RW
Greene
S
S
Day
N K
NK
D001665:Binding Sites; D015500:Chloramphenicol O-Acetyltransferase / Q000235:genetics; D004742:Enhancer Elements, Genetic / Q000187:drug effects* / Q000502:physiology; D004815:Epidermal Growth Factor / Q000494:pharmacology*; D005260:Female; D015967:Gene Expression Regulation, Viral; D017930:Genes, Reporter; D006801:Humans; D008324:Mammary Tumor Virus, Mouse / Q000235:genetics*; D011374:Progesterone / Q000494:pharmacology; D011388:Prolactin / Q000494:pharmacology*; D012091:Repetitive Sequences, Nucleic Acid / Q000187:drug effects* / Q000235:genetics; D014157:Transcription Factors; D014162:Transfection; D016211:Transforming Growth Factor alpha / Q000494:pharmacology*; D014407:Tumor Cells, Cultured
D014157:Transcription Factors; D016211:Transforming Growth Factor alpha; D011374:Progesterone; D004815:Epidermal Growth Factor; D011388:Prolactin; D015500:Chloramphenicol O-Acetyltransferase