MgcRacGAP, a new human GTPase-activating protein for Rac and Cdc42 similar to Drosophila rotundRacGAP gene product, is expressed in male germ cells.
In a search for new partners of the activated form of Rac GTPase, we have isolated through a two-hybrid cloning procedure a human cDNA encoding a new GTPase-activating protein (GAP) for Rho family GTPases. A specific mRNA of 3.2 kilobases was detected in low abundance in many cell types and found highly expressed in testis. A protein of the predicted size 58 kDa, which we call MgcRacGAP, was detected in human testis as well as in germ cell tumor extracts by immunoblotting with antibodies specific to recombinant protein. In vitro, the GAP domain of MgcRacGAP strongly stimulates Rac1 and Cdc42 GTPase activity but is almost inactive on RhoA. N-terminal to its GAP domain, MgcRacGAP contains a cysteine-rich zinc finger-like motif characteristic of the Chimaerin family of RhoGAPs. The closest homolog of MgcRacGAP is RotundRacGAP, a product of the Drosophila rotund locus. In situ hybridization experiments in human testis demonstrate a specific expression of mgcRacGAP mRNA in spermatocytes similar to that of rotundRacGAP in Drosophila testis. Therefore, protein sequence similarity and analogous developmental and tissue specificities of gene expression support the hypothesis that RotundRacGAP and MgcRacGAP have equivalent functions in insect and mammalian germ cells. Since rotundRacGAP deletion leads to male sterility in the fruit fly, the mgcRacGAP gene may prove likewise to play a key role in mammalian male fertility.
Touré
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A
Institut Cochin de Génétique Moléculaire, INSERM Unité 257, 24 Rue du faubourg Saint Jacques, 75014 Paris, France.
Dorseuil
O
O
Morin
L
L
Timmons
P
P
Jégou
B
B
Reibel
L
L
Gacon
G
G
D000595:Amino Acid Sequence; D018797:Cell Cycle Proteins / Q000378:metabolism*; D003001:Cloning, Molecular; D004268:DNA-Binding Proteins; D029721:Drosophila Proteins; D004789:Enzyme Activation; D020558:GTP Phosphohydrolases / Q000378:metabolism*; D019204:GTP-Binding Proteins / Q000378:metabolism*; D020690:GTPase-Activating Proteins; D006801:Humans; D008297:Male; D064168:Minichromosome Maintenance Complex Component 7; D008969:Molecular Sequence Data; D009687:Nuclear Proteins; D011506:Proteins / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism*; D012333:RNA, Messenger / Q000302:isolation & purification; D017422:Sequence Analysis, DNA; D017386:Sequence Homology, Amino Acid; D015398:Signal Transduction; D013094:Spermatozoa / Q000502:physiology*; D014018:Tissue Distribution; D020744:rac GTP-Binding Proteins
D018797:Cell Cycle Proteins; D004268:DNA-Binding Proteins; D029721:Drosophila Proteins; D020690:GTPase-Activating Proteins; C491087:Mcm7 protein, Drosophila; D009687:Nuclear Proteins; D011506:Proteins; D012333:RNA, Messenger; D020558:GTP Phosphohydrolases; D019204:GTP-Binding Proteins; C101624:MCM7 protein, human; D064168:Minichromosome Maintenance Complex Component 7; D020744:rac GTP-Binding Proteins