Redistribution of the discs large tumor suppressor protein during mitosis.
Drosophila discs large (Dlg) has been shown to be an essential regulator of cell polarity and attachment, and is classified as a potential tumour suppressor in higher eukaryotes. Human Dlg is expressed in epithelial cells at sites of cell-cell contact and acts as a negative regulator of cell growth. Although hDlg has been shown to be phosphorylated during mitosis, little is known about its activity during this stage of the cell cycle. To investigate this further we have analysed in detail the pattern of hDlg expression during mitotic cell division. In early mitosis there is a marked increase in membrane-bound hDlg which is then retained throughout mitosis, while during cytokinesis, there is a specific concentration of hDlg at the midbody. Using mutants of Dlg we show that this is mediated by sequences in the carboxy terminal region of Dlg, but it does not require the SH3 or PDZ domains, and is independent of binding to protein 4.1. Finally, using a mutant of Dlg that consists of just this carboxy terminal region of the protein, we show that it can compete with endogenous hDlg for midbody accumulation, and this mutant also gives rise to altered cell growth. We conclude that localisation of Dlg to the midbody indicates a role for Dlg at this critical point in cytokinesis.
International Centre for Genetic Engineering and Biotechnology, Padriciano 99, I-34012 Trieste, Italy.
Paola
P
Massimi
Daniela
D
Gardiol
Sally
S
Roberts
Lawrence
L
Banks
D048868:Adaptor Proteins, Signal Transducing; D000818:Animals; D001859:Bone Neoplasms / Q000378:metabolism / Q000473:pathology*; D002455:Cell Division; D002465:Cell Movement; D048429:Cell Size; D002478:Cells, Cultured; D003094:Collagen; D003598:Cytoskeletal Proteins; D004252:DNA Mutational Analysis; D000074288:Discs Large Homolog 1 Protein; D004338:Drug Combinations; D016147:Genes, Tumor Suppressor / Q000502:physiology; D051528:Guanylate Kinases; D006801:Humans; D015603:Keratinocytes / Q000166:cytology* / Q000378:metabolism; D007668:Kidney / Q000378:metabolism; D007797:Laminin; D008565:Membrane Proteins / Q000378:metabolism; D051379:Mice; D008813:Mice, Inbred ICR; D018613:Microscopy, Confocal; D008938:Mitosis; D009479:Neuropeptides; D012516:Osteosarcoma / Q000378:metabolism / Q000473:pathology*; D011506:Proteins / Q000235:genetics / Q000378:metabolism*; D011509:Proteoglycans
D048868:Adaptor Proteins, Signal Transducing; D003598:Cytoskeletal Proteins; C513314:DLG1 protein, human; D000074288:Discs Large Homolog 1 Protein; C000614189:Dlg1 protein, mouse; D004338:Drug Combinations; D007797:Laminin; D008565:Membrane Proteins; D009479:Neuropeptides; D011506:Proteins; D011509:Proteoglycans; C028841:erythrocyte membrane band 4.1 protein; C120557:erythrocyte membrane protein band 4.1-like 1; C059485:matrigel; D003094:Collagen; D051528:Guanylate Kinases