An alternatively spliced mRNA from the AP-2 gene encodes a negative regulator of transcriptional activation by AP-2

Mol Cell Biol. 1993 Jul;13(7):4174-85. doi: 10.1128/mcb.13.7.4174-4185.1993.

Abstract

AP-2 is a retinoic acid-inducible and developmentally regulated activator of transcription. We have cloned an alternative AP-2 transcript (AP-2B) from the human teratocarcinoma cell line PA-1, which encodes a protein differing in the C terminus from the previously isolated AP-2 protein (AP-2A). This protein contains the activation domain of AP-2 and part of the DNA binding domain but lacks the dimerization domain which is necessary for DNA binding. Analysis of overlapping genomic clones spanning the entire AP-2 gene proves that AP-2A and AP-2B transcripts are alternatively spliced from the same gene. Both transient and stable transfection experiments show that AP-2B inhibits AP-2 transactivator function, as measured by an AP-2-responsive chloramphenicol acetyltransferase reporter plasmid. Furthermore, constitutive AP-2B expression in PA-1 cells causes a retinoic acid-resistant phenotype, anchorage-independent growth in soft agar, and tumorigenicity in nude mice, in a fashion similar to transformation of these cells by oncogenes. To determine the mechanism by which AP-2B exerts its inhibitory function, we purified bacterially expressed AP-2A and AP-2B proteins. While bacterial AP-2B does not bind an AP-2 consensus site, it strongly inhibits binding of the endogenous AP-2 present in PA-1 cell nuclear extracts. However, DNA sequence-specific binding of bacterially expressed AP-2A cannot be inhibited by bacterially expressed AP-2B. Therefore, inhibition of AP-2 activity by the protein AP-2B may require an additional factor or modification supplied by nuclear extracts.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Alternative Splicing*
  • Amino Acid Sequence
  • Animals
  • Base Sequence
  • Cell Differentiation
  • Cell Division
  • Cloning, Molecular
  • DNA / metabolism
  • DNA-Binding Proteins / genetics*
  • DNA-Binding Proteins / metabolism
  • Drosophila
  • Drosophila Proteins
  • Female
  • Humans
  • Mice
  • Mice, Nude
  • Molecular Sequence Data
  • Polymerase Chain Reaction
  • Transcription Factor AP-2
  • Transcription Factors / genetics*
  • Transcription Factors / metabolism
  • Transcription, Genetic*
  • Transcriptional Activation
  • Tretinoin / pharmacology
  • Tumor Cells, Cultured

Substances

  • DNA-Binding Proteins
  • Drosophila Proteins
  • TfAP-2 protein, Drosophila
  • Transcription Factor AP-2
  • Transcription Factors
  • Tretinoin
  • DNA

Associated data

  • GENBANK/M61156