title: Induction of the long noncoding RNA NBR2 from the bidirectional BRCA1 promoter under hypoxic conditions.
abstract: BRCA1 plays an important role in preventing breast cancer and is often silenced or repressed in sporadic cancer. The BRCA1 promoter is bidirectional: it drives transcription of the long non-coding (lnc) NBR2 transcript in the opposite orientation relative to the BRCA1 transcript. Hypoxic conditions repress BRCA1 transcription, but their effect on expression of the NBR2 transcript has not been reported. We used quantitative RT-PCR to measure BRCA1 and NBR2 transcript levels in 0% and 1% oxygen in MCF-7 breast cancer cells and found that NBR2 transcript levels increased as a function of time under hypoxic conditions, whereas BRCA1 mRNA levels were repressed. Hypoxic conditions were ineffective in reducing BRCA1 mRNA in the UACC-3199 breast cancer cell line, which is reported to have an epigenetically silenced BRCA1 promoter, even though appreciable levels of BRCA1 and NBR2 mRNA were detected. Significant recovery back to baseline RNA levels occurred within 48h after the MCF-7 cells were restored to normoxic conditions. We used a construct with the 218bp minimal BRCA1 promoter linked to marker genes to show that this minimal promoter repressed expression bidirectionally under hypoxic conditions, which suggests that the elements necessary for induction of NBR2 are located elsewhere.
authors.affiliation: University of Utah School of Medicine, Salt Lake City, UT 84132, United States.
authors.forename: J Erin
authors.initials: JE
authors.lastname: Wiedmeier
authors.affiliation: Oregon Institute of Occupational Health Sciences, Oregon Health & Science University, Portland, OR, 97239, United States.
authors.forename: Anna
authors.initials: A
authors.lastname: Ohlrich
authors.affiliation: University of Utah School of Medicine, Salt Lake City, UT 84132, United States.
authors.forename: Adrian
authors.initials: A
authors.lastname: Chu
authors.affiliation: Nzumbe Inc., Portland, OR, 97201, United States.
authors.forename: Michael R
authors.initials: MR
authors.lastname: Rountree
authors.affiliation: Oregon Institute of Occupational Health Sciences, Oregon Health & Science University, Portland, OR, 97239, United States; Department of Molecular and Medical Genetics, Oregon Health & Science University, Portland, OR, 97239, United States. Electronic address: turkerm@ohsu.edu.
authors.forename: Mitchell S
authors.initials: MS
authors.lastname: Turker
mesh_terms: D019313:BRCA1 Protein / Q000235:genetics* / Q000378:metabolism; D001943:Breast Neoplasms / Q000235:genetics* / Q000503:physiopathology; D015687:Cell Hypoxia; D005260:Female; D015972:Gene Expression Regulation, Neoplastic; D006801:Humans; D009363:Neoplasm Proteins / Q000235:genetics*; D011401:Promoter Regions, Genetic / Q000235:genetics*; D062085:RNA, Long Noncoding / Q000235:genetics*; D012333:RNA, Messenger / Q000235:genetics; D060888:Real-Time Polymerase Chain Reaction; D020133:Reverse Transcriptase Polymerase Chain Reaction; D014157:Transcription Factors / Q000235:genetics*; D014407:Tumor Cells, Cultured
chemical_list: D019313:BRCA1 Protein; C492913:BRCA1 protein, human; C107422:NBR2 lncRNA, human; D009363:Neoplasm Proteins; D062085:RNA, Long Noncoding; D012333:RNA, Messenger; D014157:Transcription Factors
keywords: BRCA1; Hypoxia; NBR2; lncRNA