Growth factors-hormones and cell-bound signals thatstimulate orinhibit cellproliferation.2.Receptors-membrane-bound proteins that accept signals3Signal transducers relay messages.Transcription factors activate the expression of genes.(c)InhibitinggrowthfactorReceptorSignaltransducersTranscriptionfactorEProteinthatblocksDNAcell from dividing19-6
Copyright © The McGraw-Hill Companies, Inc. Permission required to reproduce or display 19-6 1. Growth factors Growth factors – hormones and cell hormones and cell-bound signals that bound signals that stimulate or inhibit cell proliferation. stimulate or inhibit cell proliferation. 2. Receptors Receptors – membrane membrane-bound proteins that accept signals. bound proteins that accept signals. 3. Signal transducers Signal transducers relay messages. relay messages. 4. Transcription factors Transcription factors activate the expression of genes. activate the expression of genes
The small GTPaseRASis involved in growthfactorsignaling(d)GrowthfactorReceptorRASRASRAS inactiveRASactiveGDPGTPwhenboundwhenboundtoGDPtoGTPMAPkinasecascade1TranscriptionfactorProliferation19-7Fig.19.12
Copyright © The McGraw-Hill Companies, Inc. Permission required to reproduce or display 19-7 The small The small GTPase RAS is involved in growth factor RAS is involved in growth factor signaling signaling Fig. 19.12
Cell cycle and its regulationDNA synthesisG1G2MDNA segregation19-8
Copyright © The McGraw-Hill Companies, Inc. Permission required to reproduce or display 19-8 Cell cycle and its regulation Cell cycle and its regulation S M DNA synthesis DNA segregation G1 G2
The length of cell cycle varies with each organismMFertilizedXenopusegg0.5hrMG1G224 hrCultured fibroblastMG1G2Saccharomyces cerevisiae2hrSG1G2M2.5 hrSchizosaccharomyces pombe19-9
Copyright © The McGraw-Hill Companies, Inc. Permission required to reproduce or display 19-9 Cultured fibroblast Saccharomyces cerevisiae Schizosaccharomyces pombe Fertilized Xenopus egg 24 hr 2 hr 2.5 hr 0.5 hr G1 G1 G1 S S S S G2 G2 G2 M M M M The length of cell cycle varies with each organism
Experiments with yeast helped identify genesthat control cell divisionThe budding yeastThefission yeastSchizosaccharomyces pombeSaccharomyces cerevisiae19-10
Copyright © The McGraw-Hill Companies, Inc. Permission required to reproduce or display 19-10 Experiments with yeast helped identify genes Experiments with yeast helped identify genes that control cell division that control cell division The budding yeast Saccharomyces cerevisiae The fission yeast Schizosaccharomyces pombe