Dimerization of CtIP, a BRCA1- and CtBP-interacting protein, is mediated by an N-terminal coiled-coil motif

Dubin, MJ; Stokes, PH; Sum, EYM; Williams, RS; Valova, VA; Robinson, PJ; Lindeman, GJ; Glover, JNM; Visvader, JE; Matthews, JM

Author(s): Dubin, MJ; Stokes, PH; Sum, EYM; Williams, RS; Valova, VA; Robinson, PJ; Lindeman, GJ; Glover, JNM; Visvader, JE; Matthews, JM;
Details: Publication Year 2004-06-25,Volume 279,Issue #26,Page 26932-26938
Journal Title: JOURNAL OF BIOLOGICAL CHEMISTRY
Publication Type: Journal Article
Abstract: CtIP is a transcriptional co-regulator that binds a number of proteins involved in cell cycle control and cell development, such as CtBP (C terminus-binding protein), BRCA1 (breast cancer-associated protein-1), and LMO4 (LIM-only protein-4). The only recognizable structural motifs within CtIP are two putative coiled-coil domains located near the N and C termini of the protein. We now show that the N-terminal coiled coil (residues 45-160), but not the C-terminal coiled coil, mediates homodimerization of CtIP in mammalian 293T cells. The N-terminal coiled coil did not facilitate binding to LMO4 and BRCA1 proteins in these cells. A protease-resistant domain (residues 27-168) that minimally encompasses the putative N-terminal coiled coil was identified by matrix-assisted laser desorption ionization time-of-flight mass spectrometry. This region is predicted to contain two smaller coiled-coil regions. The CtIP-(45-160) dimerization domain is helical and dimeric, indicating that the domain does form a coiled coil. The two smaller domains, CtIP( 45-92) and CtIP-(93-160), also formed dimers of lower binding affinity, but with less helical content than the longer peptide. The hydrodynamic radius of CtIP-(45-160) is the same as those of CtIP-(45-92) and CtIP-(93-160), implying that CtIP-(45-160) does not form a single long coiled coil, but a more compact structure involving homodimerization of the two smaller coiled coils, which fold back as a four-helix bundle or other compact structure. These results suggest a specific model for CtIP homodimerization via its N terminus and contribute to an improved understanding of how this protein might assemble other factors required for its role as a transcriptional corepressor.
Publisher: AMER SOC BIOCHEMISTRY MOLECULAR BIOLOGY INC
Keywords: RETINOBLASTOMA TUMOR-SUPPRESSOR; LARGE T-ANTIGEN; CRYSTAL-STRUCTURE; TRANSCRIPTION FACTORS; BINDING-PROTEIN; GENE-PRODUCT; DNA-DAMAGE; BRCA1; DOMAIN; REPRESSION
Publisher's Version: https://doi.org/10.1074/jbc.M313974200
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Creation Date: 2004-06-25 12:00:00