During apoptosis of tumor cells HMGA1a protein undergoes methylation: identification of the modification site by mass spectrometry.
Programmed cell death is characterized by posttranslational modifications of a limited and specific set of nuclear proteins. We demonstrate that during apoptosis of different types of tumor cells there is a monomethylation of the nuclear protein HMGA1a that is associated to its previously described hyperphosphorylation/dephosphorylation process. HMGA1a methylation is strictly related to the execution of programmed cell death and is a massive event that involves large amounts of the protein. In some tumor cells, HMGA1a protein is already methylated to an extent that depends on cell type. The degree of methylation in any case definitely increases during apoptosis. In the studied cell systems (human leukaemia, human prostate tumor, and rat thyroid transformed cells) among the low-molecular-mass HMG proteins, only HMGA1a was found to be methylated. A tryptic digestion map of HPLC-purified HMGA1a protein showed that methylation occurs at arginine 25 in the consensus G(24)R(25)G(26) that belongs to one of the DNA-binding AT-hooks of the protein. An increase of HMGA1a methylation could be related to heterochromatin and chromatin remodeling of apoptotic cells.
Sgarra
Riccardo
R
Dipartimento di Biochimica, Biofisica e Chimica delle Macromolecole, Università di Trieste, via L. Giorgieri 1, 34127 Trieste, Italy.
Diana
Francesca
F
Bellarosa
Cristina
C
Dekleva
Vesna
V
Rustighi
Alessandra
A
Toller
Matteo
M
Manfioletti
Guidalberto
G
Giancotti
Vincenzo
V
D000595:Amino Acid Sequence; D000818:Animals; D017209:Apoptosis; D001120:Arginine / Q000737:chemistry; D001483:Base Sequence; D001665:Binding Sites; D018076:DNA, Complementary / Q000235:genetics; D018922:HL-60 Cells; D025741:HMGA1a Protein / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D008297:Male; D013058:Mass Spectrometry; D008745:Methylation; D008969:Molecular Sequence Data; D010449:Peptide Mapping; D011471:Prostatic Neoplasms / Q000378:metabolism; D051381:Rats; D011994:Recombinant Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D017386:Sequence Homology, Amino Acid; D014407:Tumor Cells, Cultured
D018076:DNA, Complementary; D011994:Recombinant Proteins; D025741:HMGA1a Protein; D001120:Arginine