SUMOylation of the hepatoma-derived growth factor negatively influences its binding to chromatin.
Hepatoma-derived growth factor is a nuclear targeted mitogen containing a PWWP domain that mediates binding to DNA. To date, almost nothing is known about the molecular mechanisms of the functions of hepatoma-derived growth factor, its routes of secretion and internalization or post-translational modifications. In the present study, we show for the first time that hepatoma-derived growth factor is modified by the covalent attachment of small ubiquitin-related modifier 1 (SUMO-1), a post-translational modification with regulatory functions for an increasing number of proteins. Using a basal SUMOylation system in Escherichia coli followed by a MALDI-TOF-MS based peptide analysis, we identified the lysine residue SUMOylated located in the N-terminal part of the protein adjacent to the PWWP domain. Surprisingly, this lysine residue is not part of the consensus motif described for SUMOylation. With a series of hepatoma-derived growth factor mutants, we then confirmed that this unusual location is also used in mammalian cells and that SUMOylation of hepatoma-derived growth factor takes place in the nucleus. Finally, we demonstrate that SUMOylated hepatoma-derived growth factor is not binding to chromatin, in contrast to its unSUMOylated form. These observations potentially provide new perspectives for a better understanding of the functions of hepatoma-derived growth factor.
Thakar
Ketan
K
 Department of Biochemistry, Centre for Biomolecular Interactions Bremen (CBIB), University of Bremen, Germany.
Niedenthal
Rainer
R
 Department of Biochemistry, Hannover Medical School, Germany.
Okaz
Elwy
E
 Department of Biochemistry, Centre for Biomolecular Interactions Bremen (CBIB), University of Bremen, Germany.
Franken
Sebastian
S
Department of Physiological Chemistry, Rheinische-Friedrich-Wilhelm University of Bonn, Germany.
Jakobs
Astrid
A
 Department of Biochemistry, Hannover Medical School, Germany.
Gupta
Shivangi
S
 Department of Biochemistry, Centre for Biomolecular Interactions Bremen (CBIB), University of Bremen, Germany.
Kelm
Sørge
S
 Department of Biochemistry, Centre for Biomolecular Interactions Bremen (CBIB), University of Bremen, Germany.
Dietz
Frank
F
 Department of Biochemistry, Centre for Biomolecular Interactions Bremen (CBIB), University of Bremen, Germany.
D000595:Amino Acid Sequence; D000818:Animals; D051792:Basic Helix-Loop-Helix Proteins / Q000378:metabolism; D019556:COS Cells; D002522:Chlorocebus aethiops; D002843:Chromatin / Q000378:metabolism*; D016384:Consensus Sequence; D015536:Down-Regulation / Q000235:genetics; D004926:Escherichia coli; D006801:Humans; D036341:Intercellular Signaling Peptides and Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D008969:Molecular Sequence Data; D011485:Protein Binding; D011499:Protein Processing, Post-Translational / Q000235:genetics; D017434:Protein Structure, Tertiary; D025842:SUMO-1 Protein / Q000378:metabolism* / Q000502:physiology
D051792:Basic Helix-Loop-Helix Proteins; D002843:Chromatin; D036341:Intercellular Signaling Peptides and Proteins; D025842:SUMO-1 Protein; C500942:ATOH1 protein, human; C051610:hepatoma-derived growth factor