In vivo posttranslational modifications of the high mobility group A1a proteins in breast cancer cells of differing metastatic potential

Biochemistry. 2004 Sep 14;43(36):11500-15. doi: 10.1021/bi049833i.

Abstract

The high mobility group (HMG) proteins are important modulators of chromatin structure and gene transcription. Overexpression of HMGA1 proteins in vivo induces neoplastic transformation and promotes a highly metastatic cellular phenotype. This study focuses on characterization of HMGA1a in vivo posttranslational modification (PTM) patterns found in a nonmetastatic and two metastatic lines of MCF-7 human breast cancer cells of differing tumorigenic potential. PTM types and the amino acids on which they occur were identified by matrix-assisted laser desorption ionization time-of-flight (MALDI-TOF) mass spectrometry. Mass analysis was restricted to MALDI peaks having less than +/-150 parts per million (ppm) error, thereby holding our analysis to a more stringent criterion than previously published work with the HMG proteins. Validation of MALDI-TOF MS analysis was accomplished utilizing electrospray ionization tandem mass spectrometry (ESI MS/MS) and manual analysis of ion fragmentation spectra. Patterns and sites of PTMs identified in this study suggest that HMGA1a proteins, like the histones, exhibit a biochemical modification "code" that relates to cellular function. For example, both increased levels of acetylation and a previously unidentified dimethylation of both lysine and arginine residues were found on HMGA1a proteins from metastatic cells compared to proteins found in their nonmetastatic precursors. Additionally, the types of modification present on lysine-45 (e.g., unmodified, acetylation, or dimethylation) varied, depending on the metastatic potential of cells. These findings suggest that examination of the PTM patterns on HMGA1 proteins may provide valuable information concerning the physiological and phenotypic state of mammalian cells.

Publication types

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

MeSH terms

  • Amino Acid Sequence
  • Breast Neoplasms / genetics
  • Breast Neoplasms / metabolism*
  • Breast Neoplasms / pathology*
  • Cell Line, Tumor
  • Cell Transformation, Neoplastic / genetics
  • Cell Transformation, Neoplastic / metabolism
  • Cell Transformation, Neoplastic / pathology
  • HMGA1a Protein / biosynthesis
  • HMGA1a Protein / genetics
  • HMGA1a Protein / metabolism*
  • Humans
  • Molecular Sequence Data
  • Neoplasm Metastasis / genetics
  • Neoplasm Metastasis / pathology*
  • Peptide Fragments / biosynthesis
  • Peptide Fragments / genetics
  • Peptide Fragments / metabolism
  • Phenotype
  • Phosphorylation
  • Protein Processing, Post-Translational* / genetics
  • Recombinant Proteins / biosynthesis
  • Recombinant Proteins / genetics
  • Recombinant Proteins / metabolism
  • Spectrometry, Mass, Electrospray Ionization
  • Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization
  • Transfection

Substances

  • Peptide Fragments
  • Recombinant Proteins
  • HMGA1a Protein