title: Molecular weight abnormalities of the CTCF transcription factor: CTCF migrates aberrantly in SDS-PAGE and the size of the expressed protein is affected by the UTRs and sequences within the coding region of the CTCF gene.
abstract: CTCF belongs to the Zn finger transcription factors family and binds to the promoter region of c-myc. CTCF is highly conserved between species, ubiquitous and localised in nuclei. The endogenous CTCF migrates as a 130 kDa (CTCF-130) protein on SDS-PAGE, however, the open reading frame (ORF) of the CTCF cDNA encodes only a 82 kDa protein (CTCF-82). In the present study we investigate this phenomenon and show with mass-spectra analysis that this occurs due to aberrant mobility of the CTCF protein. Another paradox is that our original cDNA, composed of the ORF and 3'-untranslated region (3'-UTR), produces a protein with the apparent molecular weight of 70 kDa (CTCF-70). This paradox has been found to be an effect of the UTRs and sequences within the coding region of the CTCF gene resulting in C-terminal truncation of CTCF-130. The potential attenuator has been identified and point-mutated. This restored the electrophoretic mobility of the CTCF protein to 130 kDa. CTCF-70, the aberrantly migrating CTCF N-terminus per se, is also detected in some cell types and therefore may have some biological implications. In particular, CTCF-70 interferes with CTCF-130 normal function, enhancing transactivation induced by CTCF-130 in COS6 cells. The mechanism of CTCF-70 action and other possible functions of CTCF-70 are discussed.
authors.affiliation: Genetics Unit, Department of Biochemistry, University of Oxford, South Parks Road, Oxford OX1 3QU, UK. klenovae@bioch.ox.ac.uk
authors.forename: E M
authors.initials: EM
authors.lastname: Klenova
authors.forename: R H
authors.initials: RH
authors.lastname: Nicolas
authors.forename: S
authors.initials: S
authors.lastname: U
authors.forename: A F
authors.initials: AF
authors.lastname: Carne
authors.forename: R E
authors.initials: RE
authors.lastname: Lee
authors.forename: V V
authors.initials: VV
authors.lastname: Lobanenkov
authors.forename: G H
authors.initials: GH
authors.lastname: Goodwin
mesh_terms: D000818:Animals; D019556:COS Cells; D018076:DNA, Complementary; D004591:Electrophoresis, Polyacrylamide Gel; D008970:Molecular Weight; D016366:Open Reading Frames; D017354:Point Mutation; D014176:Protein Biosynthesis; D014157:Transcription Factors / Q000737:chemistry* / Q000235:genetics*; D015533:Transcriptional Activation
chemical_list: D018076:DNA, Complementary; D014157:Transcription Factors