Cell Cycle

Cell Cycle - 4 8 etc Isolated proteins and looked at...

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Cell Cycle (180 – 192) Prokaryotes can simultaneously duplicate and segregate HARTWELL Budding yeast cell cycle Why yeast? simple eukaryote, divides fast, genetic tools for yeast are well developed Mutagenize yeast screen for temperature sensitive mutants 25C: mutation has no effect 75C: mutation appears, cells arrested in growth “CDC” (cell division cycle) mutants Different CDC mutants cells stop at different phases, so whole colony looks the same CDC 28 NURSE Wants to find fission yeast equivalent of CDC28 Tried to find cells that are too big (can’t divide) Instead, found cells that are too small premature division = “wee mutants” Isolated 6 mutants, 5 are in gene wee 1 , 6 th gene = CDC2 Complementation : CDC2 is functionally equivalent to CDC28 Later found that CDC2/CDC28 makes a protein kinase Same CDC protein regulates cell cycle in yeast + humans HUNT Sea urchin eggs Divisions are synchronized: 2
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Unformatted text preview: 4 8, etc. Isolated proteins and looked at protein expression at 10 minute intervals Oscillating protein levels are related to cell division cycles calls protein cyclin (A and B) Cyclin is always made- oscillation comes from regulated degradation Cyclin is similar to MPF … purify MPF MPF = cyclin + CDC2/28 (aka CDK, cyclin dependent kinase I) CDK is only active when bound to cyclin MASUI Frog eggs- oocyte maturation in vitro In vivo , progesterone leads to meiosis Take egg arrested in metaphase II transfer cytoplasm to G2-arrested oocyte maturation Some factor in cytoplasm induces maturation MPF = maturation promoting factor MPF activity is LOW/G2, HIGH/M1, LOW/I, HIGH/M2, LOWI … etc … oscillates Cyclin high CDK1 on mitosis Cyclin low CDK1 off S G2 M G1 S-cyclin and M-cyclin bind to CDK to start S and M phases- degraded after phase...
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Cell Cycle - 4 8 etc Isolated proteins and looked at...

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