Rox, a novel bHLHZip protein expressed in quiescent cells that heterodimerizes with Max, binds a non-canonical E box and acts as a transcriptional repressor

Germana Meroni, Alexandre Reymond, Myriam Alcalay, Giuseppe Borsani, Akira Tanigami, Rossana Tonlorenzi, Cristiana Lo Nigro, Silvia Messali, Massimo Zollo, David H. Ledbetter, Roger Brent, Andrea Ballabio, Romeo Carrozzo

Research output: Contribution to journalArticle

Abstract

Proteins of the Myc and Mad family are involved in transcriptional regulation and mediate cell differentiation and proliferation. These molecules share a basic-helix-loop-helix leucine zipper domain (bHLHZip) and bind DNA at the E box (CANNTG) consensus by forming heterodimers with Max. We report the isolation, characterization and mapping of a human gene and its mouse homolog encoding a new member of this family of proteins, named Rox. Through interaction mating and immunoprecipitation techniques, we demonstrate that Rox heterodimerizes with Max and weakly homodimerizes. Interestingly, bandshift assays demonstrate that the Rox-Max heterodimer shows a novel DNA binding specificity, having a higher affinity for the CACGCG site compared with the canonical E box CACGTG site. Transcriptional studies indicate that Rox represses transcription in both human HEK293 cells and yeast. We demonstrate that repression in yeast is through interaction between the N-terminus of the protein and the Sin3 co-repressor, as previously shown for the other Mad family members. ROX is highly expressed in quiescent fibroblasts and expression markedly decreases when cells enter the cell cycle. Moreover, ROX expression appears to be induced in U937 myeloid leukemia cells stimulated to differentiate with 12-O-tetradecanoylphorbol-13-acetate. The identification of a novel Max-interacting protein adds an important piece to the puzzle of Myc/Max/Mad coordinated action and function in normal and pathological situations. Furthermore, mapping of the human gene to chromosome 17p13.3 in a region that frequently undergoes loss of heterozygosity in a number of malignancies, together with the biochemical and expression features, suggest involvement of ROX in human neoplasia.

Original languageEnglish
Pages (from-to)2892-2906
Number of pages15
JournalEMBO Journal
Volume16
Issue number10
DOIs
Publication statusPublished - May 15 1997

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Keywords

  • bHLHZip proteins
  • Max-interacting proteins
  • Myc
  • sin3
  • Transcriptional repressor

ASJC Scopus subject areas

  • Genetics
  • Cell Biology

Cite this

Meroni, G., Reymond, A., Alcalay, M., Borsani, G., Tanigami, A., Tonlorenzi, R., Lo Nigro, C., Messali, S., Zollo, M., Ledbetter, D. H., Brent, R., Ballabio, A., & Carrozzo, R. (1997). Rox, a novel bHLHZip protein expressed in quiescent cells that heterodimerizes with Max, binds a non-canonical E box and acts as a transcriptional repressor. EMBO Journal, 16(10), 2892-2906. https://doi.org/10.1093/emboj/16.10.2892