%T Catalysis of guanine nucleotide exchange on ran by the mitotic regulator RCC1
%J Nature
%V 354
%P 80
%K RCC1, pim1, spi1, ras, ran
%X RCC1 is a mitotic regulator from BHK with homology to pim1 in pombe.
HeLa RCC1 is complexed to a 25kDa protein related to ras, and is GTP/GDP binding, called ran. The pombe homolog is spi1.
RCC1 acts on ran in the same way as nucleotide exchange factors act on ras, exchanging GTP for GDP, activating ras. Ran.GTP is presumably activated (and GTP hydrolysed) by an as yet unidentified GAP analog.
RCC1 has not been shown to vary in activity over the cell cycle, although yeast has shown a link of misosis to S phase involving pim1. Spi1 overexpression rescues pim1-, though not pim1del. Probably due to compensatory levels of Spi1.GTP
%A Crabtree GW
%A Henderson JF
%D 1971
%T Rate limiting steps in the interconversion of purine ribonucleotides in Ehrlich Ascites tumor cells in vitro
%J Cancer Research
%V 31
%P 985-991
%K NTP conversion
%X Conversion of inosinate to guanylate is limited first by glutamine concentration and second by iosinate.
Conversion of iosinate to adenylate is limited by isoinate.
Adenylate -> guanylate limited by glutamine, and then probably adenylate deaminase. Guanylate to adenylate limited by guanylate reductase.
%A Dasso M
%D 1993
%T RCC1 in the cell cycle: the regulator of chromosome condensation takes on new roles
%J TIBS
%V 18
%P 96-101
%K RCC1, tsBN2, pim1, spi1
%X Review: functions of RCC1
RCC1 is the only gene found so far in the detection of unreplicated DNA that binds chromatin. PCC in tsBN2 is a genuine attempt at mitosis: nuclear envelope breakdown, spindle formation, MPF activation all occur.
tsBN2 at restr. temp. also inhibits transcription, though not as rapidly as replication.
RCC1 is lost from DNA at mitosis. Release also occurs following treatment with DNA intercalating agents.
Human RCC1 complements ts but not null mutations of the S. cerevisiae gene PRP20/SRM1/MTR1. This gene was found through several screenings:
SRM1 - Mating pathway, PRP20 - mRNA splicing and 3' end formation, MTR1 - mRNA export from nucleus
Yeast homolog is pim1.
No cell cycle specific expression observed; control is probably by post-translational modification.
All RCC1 homologs display interphase nuclear localisation, and all except SRM1 are displaced from DNA at mitosis.
Structure: N-terminal basic DNA binding region, followed by 7 tandem repeats each 50-60 aa. Drosophila homolog has additional C-terminal region.
DNA binding is not essential for activity (although activity is much lower). Neither is it sufficient; mutants in activity are known which still bind DNA.
Binds to highly abundant protein ran (25:1 excess). GAP protein is still not known,
%A Dasso M
%A Nishitani H et al
%D 1992
%T RCC1, a Regulator of Mitosis, Is Essential for DNA Replication
%J MCB
%V 12
%P 3337-3345
%K BHK, PCC, RCC1, replication
%X ts BHK mutants go into S phase PCC
Depletion in Xenopus egg extracts prevents replication of added sperm DNA. No effect on replication of ssDNA => not part of replication apparatus, but possibly part of the initiation of replication.
see Seino et al (92) for further work on ts BHK mutants, and Dasso (93) for review.
%A Day RS
%D 1993
%T Deoxyguanosine reverses inhibition by hydroxyurea of repair of UV-irradiated adenovirus 5
%J Mutation Res.
%V 293
%N 3
%P 215-223
%K dNTP pools, hydroxyurea
%X dG 100% reversal, dA 70%, dT 55%, dC 3%. dNTPs given at 5E-4 M.
HU treatment reduces dA and dG pools, but not dC and dT{hence effectiveness of dA and dG?}
Single strand repair most affected {Is there detection of ssDNA affected by dNTPs?}
Reductase activity is feedback controlled at two binding sites. One is pure feedback negative control, the other controls substrate specificity, depending on binding of dTTP, dGTP. dATP is inhibitory at this site also
%A Downes CS
%A Johnson RT
%A Yew FF
%D 1983
%T Effects of conditioned medium on nucleoside uptake, cell cycle progression and apparent DNA repair
%J J. Cell Sci.
%V 59
%P 145-158
%K dNTP, repair
%X Photocopy in file. Conditioned medium affects rate of uptake of nucleosides.
%A Haynes RH
%D 1985
%T Molecular mechanisms in genetic stability and change: The role of deoxyribonucleotide pool balance
%B Genetic Consequences of Nucleotide Pool Imbalance
%I Plenum Press
%C New York
%P 1-23
%K dNTP, mutation
%X Introduction to the book. Notes in file. dNTP pool bias leads to reduced replication fidelity and chromatic aberrations. Mutants in biosynthesis can be 'mutator' strains.
Some mutagens may act through causing nucleotide pool imbalance
%A Hunting D
%A Henderson JF
%D 1982
%T Methods for the determination of deoxyribonucleotide triphosphate concentrations.
%J Methods in Cancer Research
%V 20
%P 245
%K dNTPs, enzymatic assay
%X See photocopy
%A Matsumoto T
%A Beach D
%D 1991
%T Premature initiation of mitosis in yeast lacking RCC1 or an interacting GTPase
%J Cell
%V 66
%P 347
%K pombe, RCC1, pim1, spi1
%X Pombe mutant pim1 has M uncoupled from replication completion. cdc25 is not req'd for M in this mutant. pim1 is a homolog of RCC1
pim1 is rescued by overexpression of spi1, a ras-like GTPase
in Xenopus, the onset of dependent cycling with checkpoints occurs at the mid-blastula transition. Karyoplasmic ratio. Evidence: Aphidicolin (repl. inh.) only works in cell-free extracts when nuclei at high concentration.
pim1 req's both cdc2 and cdc13 to be observable, so must be upstream of MPF
At RT, cdc2 becomes transiently active in pim1- but not in +.
spi1 rescues pim1- but not spi1del
%A Murray AW
%D 1992
%T Creative blocks: cell cycle checkpoints and feedback controls
%J Nature
%V 359
%P 599-604
%K checkpoints
%X Early Xenopus embryos have no feedback; they rely on cell-cycle engine being slower than downstream events. Hartwell & Weinert argued that cells that fail are discarded, as observed in Drosophila, when such nuclei fall from the surface layer.
Most mammalian cells blocked in S phase stop growing and remain at G2 size, due to protein synthesis stopping also. When block is lifted they will resume where they left off. Rodent cells, on the other hand, continue to grow, and when the block is removed may or may not attempt mitosis and all die. This may be due to apoptosis. Protein synthesis inhibitors prevent such deaths.
{Theory: No cyclin buildup --> no rush into mitosis when block released}
Theory: RCC1 inactivation --> ran.GDP --> disappearance of replication forks.
%A Nicander B
%A Reichard P
%D 1981
%T Aphidicolin sensitivity of variant 3T6 cells selected for changes in ribonucleotide triphosphate reductase
%J Biochem. Biophys. Res. Comm.
%V 103
%P 148-155
%K dNTPs, aphidicolin
%X 2 mutants of 3T6 have resistance to aphidicolin, an inhibitor of DNA polymerase alpha:
3T6-HU-11 overproduces the active M2 subunit -> increaseed dATP and 2x normal resistance
3T6-CA/dA is mutated in the regulatory M1 subunit, and overproduces dATP and dCTP and has 7x normal resistance
Aphidicolin causes decrease in dCTP pool but not others. Aphidicolin may be competing with dNTPs for the polymerase. dCTP may have a regulatory function.
{did anyone try adding dCTP, if possible?}
%A Nishimoto T
%A Uzawa S
%A Schlegel R
%D 1992
%T Mitotic checkpoints
%J Curr Op in Cell Bio
%V 4
%P 174-179
%K review
%X Review of:
RCC1/ran/pim1/spi1/srm1/prp20
RAD9 (Brown et al 1992)
p34cdc2 (P) and cyclin binding; T161 (P) req'd
cdc25/p65 phosphatases
%A Reichard P
%D 1985
%T Ribonucleotide reductase and deoxyribonucleotide pools
%B Genetic Consequences of Nucleotide Pool Imbalance
%I Plenum Press
%C New York
%P 33-45
%X Notes in file. dNTP and ATP control of substrate specificity of ribonucleotide reductase. dATP is an overall off switch at high levels.
dCTP/dATP ratio high in cycling cells. Low in S phase arrest.
HU resistant mutants (15x wt reductase activity) have high dATP, limiting overproduction of others.
dNTP turnover is rapid - 10 pmol/min/million cells
Blocking de novo synthesis with amethopterin and HAT showed that two pools extant; synthesis preferentially from NTP sources via reductase, not from dN.
%A Roberge M
%D 1992
%T Checkpoint controls that couple mitosis to completion of DNA replication
%J Trends in Cell Bio.
%V 2
%P 277
%K RCC1, cdc2
%X Good review tying RCC1, recognition of un-replicated DNA and p34cdc2 activation.
%A Seino H
%A Hisamoto N
%A Uzawa S
%A Sekiguchi T
%A Nishimoto T
%D 1992
%T DNA binding domain of RCC1 protein is not essential for coupling mitosis with DNA replication
%J J Cell Sci
%V 102
%P 393-400
%K RCC1, tsBN2 mutant
%X If the N terminal DNA binding domain was removed it was still just as effective at rescuing the BHK21 derivative tsBN2 as wt RCC1. However the localisation of the truncated protein was not as confined to the nucleus. Sucrose gradients showed delN-RCC1 to be bound to nucleosomal proteins. N terminal has a nuclear localisation sequence, perhaps?
%A Squires S
%A Oates DJ
%A Bouffler SD
%A Johnson RT
%D 1992
%T Cockayne's Syndrome Fibroblasts are Characterized by Hypersensitivity to Deoxyguanosine and Abnormal DNA Precursor Pool Metabolism in Response to Deoxyguanosine or Ultraviolet Light
%J Somatic Cell & Mol. Gen.
%V 18
%P 387-401
%K HPLC, dNTPs
%X Shosh's work on nucleotide pools, measured by HPLC. Photocopy in file.
%A Walker DH
%A Maller JL
%D 1991
%T Role for cyclin A in the dependence of mitosis on completion of DNA replication.
%J Nature
%V 354
%P 314-317
%K cyclin A
%X Degradation of both A & B req'd for mitosis exit, but A destruction is earlier.
Ablation of cyclin A led to premature mitosis in Xenopus extracts, removing aphidicolin block. Cyclin A competing with cyclin B?
