title: A conserved region within interferon regulatory factor 5 controls breast cancer cell migration through a cytoplasmic and transcription-independent mechanism.
abstract: BACKGROUND
  Migration of breast cancer cells out of a duct or lobule is a prerequisite for invasion and metastasis. However, the factors controlling breast cancer cell migration are not fully elucidated. We previously found that expression of the transcription factor interferon regulatory factor 5 (IRF5) is significantly decreased as a breast lesion progresses from a non-malignant stage to ductal carcinoma in situ and is eventually lost in ~80% of invasive ductal carcinomas examined. Human in vitro and murine in vivo models of invasive breast cancer confirmed an important role for IRF5 in regulating cell motility, invasion and/or metastasis; yet, the mechanism(s) by which this occurs is not known. Since IRF5 is primarily expressed in the cytoplasm of human mammary epithelial cells, we hypothesized that IRF5 may function in a transcription-independent manner to control intrinsic cell migration.
  
  
  RESULTS
  A series of IRF5 deletion mutants were tested in cell motility, invasion and migration assays. A novel, conserved 10 amino acid domain was identified that regulates mammary epithelial cell migration. This region (∆115-125) is downstream of IRF5's DNA binding domain and therefore when absent, retains IRF5 transcription activity but loses cell migration control. An IRF5 construct with a mutated nuclear localization signal further confirmed that IRF5 controls migration in a cytoplasmic and transcription-independent manner. Candidate cytoskeletal molecules were identified in MDA-MB-231 cells to interact with IRF5 by immunoprecipitation and mass spectrometry analysis. α6-tubulin was independently confirmed to interact with endogenous IRF5 in MCF-10A cells. Alterations in F-actin bundling after staining EV- and IRF5-231 cells with phalloidin suggests that IRF5 may control cell migration/motility through its interaction with cytoskeletal molecules that contribute to the formation of F-actin networks. Last and most notably, we found that IRF5's control of cell migration is not restricted to mammary epithelial cells but functions in other epithelial cell types suggesting a more global role for this newly identified cell migratory function of IRF5.
  
  
  CONCLUSIONS
  These findings are significant as they identify a new regulator of epithelial cell migration and provide specific insight into the mechanism(s) by which loss of IRF5 expression in mammary epithelial cells contributes to breast cancer metastasis.
authors: Department of Microbiology, Biochemistry & Molecular Genetics, Rutgers Biomedical and Health Sciences, Newark, NJ, 07103, USA. pimentem@njms.rutgers.edu.|Rutgers Biomedical and Health Sciences, New Jersey Medical School-Cancer Center Rm. G1224, 205 South Orange Ave, Newark, NJ, 07103, USA. pimentem@njms.rutgers.edu.
authors: Erica Maria
authors: EM
authors: Pimenta
authors: Department of Microbiology, Biochemistry & Molecular Genetics, Rutgers Biomedical and Health Sciences, Newark, NJ, 07103, USA. barnesbe@njms.rutgers.edu.|Rutgers Biomedical and Health Sciences, New Jersey Medical School-Cancer Center Rm. G1224, 205 South Orange Ave, Newark, NJ, 07103, USA. barnesbe@njms.rutgers.edu.
authors: Betsy J
authors: BJ
authors: Barnes
mesh_terms: D021581:Active Transport, Cell Nucleus; D014408:Biomarkers, Tumor / Q000235:genetics / Q000378:metabolism; D001943:Breast Neoplasms / Q000235:genetics* / Q000378:metabolism / Q000401:mortality; D045744:Cell Line, Tumor; D002465:Cell Movement / Q000235:genetics; D017124:Conserved Sequence; D003593:Cytoplasm / Q000378:metabolism; D003598:Cytoskeletal Proteins / Q000378:metabolism; D004847:Epithelial Cells / Q000378:metabolism; D005260:Female; D015870:Gene Expression; D006801:Humans; D050835:Interferon Regulatory Factors / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism; D010446:Peptide Fragments / Q000235:genetics; D011379:Prognosis; D011485:Protein Binding; D054730:Protein Interaction Domains and Motifs; D014158:Transcription, Genetic
chemical_list: D014408:Biomarkers, Tumor; D003598:Cytoskeletal Proteins; C431713:IRF5 protein, human; D050835:Interferon Regulatory Factors; D010446:Peptide Fragments
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